Wastewater reuse growing unprecedented populations and increasing pressure. Free Essays

Chapter 1 Wastewater Reuse: An Overview 1.1Introduction Growing unprecedented populations and increasing pressure on the development of new water resources have prompted a variety of measures to reclaim, recycle and reuse wastewater over the last two or three decades. As part of this trend, some municipalities have commenced to reuse wastewater for non-potable water needs, such as irrigation of golf courses and parks. We will write a custom essay sample on Wastewater reuse growing unprecedented populations and increasing pressure. or any similar topic only for you Order Now In a little but increasing number of municipalities, these measures involve the use of treated wastewater to augment the general water supply. A major catalyst for the development of wastewater reuse, recycling and reclamation has been the need to provide alternative water resources to achieve water quantity requirement for industry, irrigation, urban potable and non-potable water applications. The benefits coupled with reusing treated wastewater for supplemental applications prior to disposal or discharge include environmental protection, preservation of high quality water resources and economic advantages. These â€Å"wastewater reuse† projects are made possible by reliability and effectiveness of wastewater treatment technologies that can turn municipal wastewater into reclaimed wastewater that can serve as a supplemental water resource in addition to meeting standards established by the Safe Water Drinking Act. However, important problems remain regarding the levels of testing, monitoring and treatment needed to ensure human health when reclaimed wastewater is consumed for potable purposes. Some engineering and public health professionals oppose in principle to the reuse of wastewater for potable purposes, because standard public health philosophy and engineering practice call for using the purest source possible for drinking water.1 Others worry that existing techniques might not discover all the chemical and microbial contaminants that may be present in reclaimed wastewater. Several guidelines pertaining to potable reuse of wastewater have been issued, but these guidelines o ffer conflicting guidance on whether potable is adoptable and, when it is adoptable, what safeguards should be in place. 1.2 The Earth’s Water Resources Earth is known as the â€Å"Blue Planet† because water is discovered in many places on Earth including in the atmosphere, on the surface of the Earth and within rocks below the surface. The total volume of water on the planet is about 1,360,000,000 km3. About 71 percent of Earth’s surface is covered with water, and the oceans hold about 97 percent of all Earth’s water. Figure 1.1 illustrates the approximate distribution of the locations of water on Earth, of which only about 3 percent of the Earth’s water is classified as freshwater and only about 0.91 percent is discovered in freshwater lakes, swamps, rivers and groundwater supplies available for human consumption. Figure 1.1 Distribution of water in the hydrosphere. The water cycle or hydrologic cycle describes the continuous movement of water within the hydrosphere. This indicates the cyclic movement of water evaporated from water surfaces, land surfaces and snow fields or evapotranspiration from land plants and animals to the atmosphere. Atmospheric moisture condenses into clouds and precipitated to the earth as rain, snow, hail or in some other form. Once the precipitated water has fallen to Earth, it may percolate through soil strata to form groundwater aquifers or runs off into streams, lakes, ponds and the sea. Groundwater and surface water drain toward the sea for recycling. Many sub-cycles to the global-scale hydrologic cycle exist, involving the managed transport of water, such as an aqueduct. Wastewater reuse, reclamation and recycling have become important elements of the hydrologic cycle in industrial, agricultural and urban areas. Figure 1.2 illustrates an overview of the cycling of water from ground water and surface water resources to water treatment plants, industrial, irrigation, municipal application, and to wastewater reclamation and reuse facilities. Figure 1.2 Water reuse application. 1.1Types of Water Reuse When considering the reuse of treated wastewater for potable purposes, critical distinctions must be made between â€Å"indirect† and â€Å"direct† potable reuse and between â€Å"unplanned† and â€Å"planned† potable reuse. The key distinction between indirect and direct potable reuse is that direct potable reuse does not make use of any environmental barrier. In other words, simply sending treated wastewater from a wastewater treatment facility directly to a potable water-supply distribution system or a potable source treatment facility. This practice is rarely use because of the increased potential risk to public health and the negative public perception. Indirect potable reuse is that the purified reclaimed water is pumped into a raw water supply, such as an underground aquifer or in potable water storage reservoirs, resulting in mixing, dilution and assimilation, thus providing an environmental buffer. Indirect potable reuse can be unplanned and planned. Unplanned indirect potable reuse occurs continuously in the environment. This results when a water supply has a natural source that contains unintentional addition of wastewater. Planned indirect potable reuse is common practice to artificially recharge water supply sources with reclaimed water derived from treated wastewater. The water receives additional treatment prior to distribution. The reason that indirect potable reuse is not considered to cause a health risk is that the treated wastewater benefits from natural treatment from storage in surface water and groundwater aquifer before abstraction to ensure good water quality. 1.2Overview of Wastewater Treatment Technology The problems surrounding wastewater reuse are essentially related to public health. Only in unusual situations do the substances in sewage significantly downgrade the value of water for other purposes. Many diseases are caused by organisms that may be present in wastewater. In addition, there are many toxic and carcinogenic substances present in wastewater at levels that may or may not be adequate to cause disease. The effective wastewater treatment technology to meet water quality requirements for wastewater reuse applications and to protect public health is a crucial element for wastewater reuse system. Conventional wastewater treatment consists of a combination of physical, chemical and biological processes and operations to eliminate solids, organic matter, pathogens, metals and sometime nutrients from wastewater.2 Common terms used to define different degrees of treatment, in sequence of increasing treatment level are preliminary, primary, secondary, tertiary and/or advanced treatment. In some regions, disinfection step for control pathogenic organisms sometimes follows the last treatment step. Figure 1.3 shows a generalized wastewater treatment diagram. Figure 1.3 Generalized flow diagram for conventional wastewater treatment 1.1.1 Preliminary Treatment The purpose of preliminary treatment is the removal of sands, solids and rags that would settle in channel and interfere with treatment processes. Removal of these materials is necessary to protect the operation of subsequent treatment units. Preliminary treatment of wastewater typically includes screening, grinding, grit removal, flotation, equalization and flocculation. Treatment equipment such as bar screens, comminutors and grit chambers are adopted as the wastewater first enters a wastewater treatment plant. In grit chambers, the velocity of wastewater through the chamber is retained sufficiently high, so as to avoid the settling of organic solids. Comminutors are sometimes used to supplement course screening and serve to decrease the size of particles so that they will be removed and disposed of in a landfill. 1.1.2 Primary Treatment Primary treatment is the second step in treatment and removes organic and inorganic matters from raw sewage by the physical processes. Primary treatment includes screening to trap solid matters, comminution for removal of large solids, grit removal and sedimentation by gravity to remove suspended solids. In general, about one-half of suspended solids and 20 to 50 percent of the biochemical oxygen demand are removed from the wastewater by primary treatment process. Nutrients, pathogenic organisms, trace elements and potentially toxic organic compounds that are associated with solids in wastewater can also be removed by primary treatment processes. 1.1.3 Secondary Treatment Secondary treatment systems remove the biodegradable dissolved and colloidal matter using an array of biological processes coupled with solid/liquid separation. Biological processes are engineered to provide effective microbiological metabolism of organic substrates dissolved or suspended in wastewater.2 Part of the organic matter is oxidized by the microorganisms, thereby producing carbon dioxide and other end products. The remaining organic matter in wastewater provides the materials and energy needed to sustain the microorganism community. Secondary treatment systems can remove suspended solids and up to 95 percent of the biochemical oxygen demand entering the process, as well as certain organic compounds and significant amount of heavy metals. 1.1.4 Tertiary and/or Advanced Treatment Tertiary and/or advanced treatment is adopted when specific constituents which cannot be removed by primary and secondary treatment must be removed. In general, tertiary treatment refers to additional removal of suspended material by granular medium filtration and chemical coagulation. In other cases, advanced treatment refers to more complete removal of specific constituents, such as ammonia or nitrate removal by ion exchange or total dissolved solids removal by reverse osmosis.2 These processes essentially remove more than 99 percent of all the pollutants from wastewater, producing an almost drinking water quality. 1.1.5 Disinfection The objective of disinfection in the wastewater treatment is to destroy all pathogenic microorganisms. The major groups of pathogenic microorganisms include bacteria, viruses, amoebic cysts and protozoa. In general, disinfection can be achieved by chemical or physical method that destroys pathogens. Chemical methods are based on the addition of a strong acid, alcohol or an oxidizing chemical (such as chlorine, ozone, hydrogen peroxide or bromine). Alternatively, physical methods might include heating, incineration and irradiation with ultraviolet radiation. Disinfection is frequently combined with treatment plant design, but not effectively practiced, because of the reduced effectiveness of ultraviolet radiation or the high cost of chlorine where the water is not sufficiently clear or free of particles. 1.2 Types of Contaminants An important issue for people to understand that there are various types of contaminants that may be in your water. The specific contaminants leading to pollution in water involve a wide spectrum of pathogenic organisms, inorganic chemicals and organic chemical. High concentrations of contaminants can have adverse effects to our health. 1.2.1 Pathogenic Organisms Bacterium in water, also known as pathogenic organism, is a public health hazard with risk factors in nearly all regions of the world. It is evident from the water purification attempts throughout history that human realized that drinking water could be hazardous. Several other infectious diseases can be transmitted by contaminated water. Bacterial diseases include Typhoid fever, Cholera, Shigellosis and Salmonellosis. Gastroenteritis, Hepatitis A and SARS are examples of viral disease. Parasitic diseases, such as Schistosomiasis, Ascariasis and Taeniasis, are also transmitted via water. 1.2.2 Inorganic Chemicals Wastewater contains many inorganics that present known or potential health risks if consumed. These contaminants include such compounds as lead, cadmium, chromium, arsenic, nitrate and sulphate. Arsenic and lead are cumulative chemical poisons that can result in cancer, dermal lesions, peripheral neuropathies and vascular effects. 1.2.3 Organic Chemicals In a 1980 survey, a number of organic chemicals were found in water supplies. The term organic chemicals in this sense mean that they contain carbon atoms, such as chlorinated hydrocarbons, aliphatic compounds, benzenes and phenols, which mean that they are derived from petroleum. Organic chemical can easily combine with human tissue which can cause damage that includes kidney, liver system problems and increased cancer risk. Chapter 2 Wastewater Reuse Criteria 2.1 Introduction The principal issue of concern for consumer of treated wastewater is the quality of this water includes its physical, biological, chemical and radiological characteristics. These concerns therefore necessitate the formulation of criteria, standards and guidelines that are appropriate for the consumers of this water.3 A first stage in establishing wastewater reuse regulations and guidelines is wastewater reuse criteria. Wastewater reuse criteria are principally directed at health and environmental protection and typically address wastewater treatment, reclaimed water quality, treatment reliability, distribution systems and use area controls.2 Wastewater reuse criteria imply an idea condition without a legal basic. Regulations and guidelines are different in that regulations are legally enforceable and spell out specific figures that can be used for enforcement and administrative action, which guidelines do not have legal basic and compliance is voluntary. In theUnited States, the Environment Protection Agency issued guidelines in 1992 that are intended to offer guidance to states, which have not developed their own regulations or guidelines. At the international level, the World Health Organization has developed guidelines for wastewater reuse in agriculture and aquaculture. The World Health Organization guidelines are adopted throughout the world and provide all countries with the necessary information to set their own wastewater reuse regulations or guidelines. 2.2 Wastewater Quality for Reuse Applications Table 2.1 presents general wastewater reuse applications. The types of wastewater reuse may be classified into the following six broad categories include agricultural and landscape irrigation, industrial reuse, groundwater recharge, recreational and environmental, non-potable urban uses and potable reuse. Wastewater reuse can be employed to satisfy the water demand in various fields and contribute to the freshwater resources conservation. Table 2.1 Categories of Wastewater Reuse and Potential Constraints Wastewater reuse categoryaPotential constraints Agricultural and landscape irrigation Crop irrigationEffects of salts on soils and crops. Commercial nurseriesPublic health concerns, surface and groundwater pollution, marketability of crops, and public acceptance. Parks School yards Freeway medians Golf courses Cemeteries Greenbelts Residential areas Industrial reuse CoolingScaling, corrosion, biological growth, and fouling; public health concerns. Boiler feed Process water Heavy construction Groundwater recharge Groundwater replenishmentPotential toxicity of chemicals and pathogens. Salt water intrusion Subsidence control Recreational and environment Lakes and pondsHealth concerns and eutrophication. Marsh enhancement Streamflow augmentation Fisheries Snowmaking Non-potable urban uses Fire protectionPublic health, foulinf, scaling, corrosion, and biological growth. Air conditioning Toilet flushing Potable reuse Blending in water supplyPotential toxic chemicals, public health, and public acceptance. Pipe-to-pipe water supply a Arranged in descending order of anticipated volume of use. From Asano, T.D., et al., Water Environ. Technol., 4, 36, 1992. 2.2.1Wastewater Reuse for Agricultural Irrigation By far the biggest user of wastewater is agriculture throughout the entire semi-tropical and arid tropical areas of the world. Agriculture receives 67 percent of total water withdrawal and account for 86 percent of consumption in 2000. In Asia and Africa, an estimated 85 to 90 percent of all the freshwater use is for agriculture. By 2025, agriculture is anticipated to increase its water demands by 1.2 times. Therefore, wastewater reuse is important for sustainable water management. The reuse of wastewater for agriculture has some benefits as well as some disbenefits.4, 5 Benefits include the following: Source of extra irrigation water. Conservation of freshwater for other beneficial uses. Low cost source of a water supply. Alternative way to dispose of wastewater and avoid pollution and sanitary issues. Dependable, continuous water source. Effective use of plant nutrients contained in the wastewater, such as nitrogen and phosphorus. Provides extra treatment of the wastewater before being recharged to the groundwater. Disbenefits include the following: Wastewater not properly treated can cause potential public health issues. Hazardous chemical contamination of groundwater. Certain soluble constituents in the wastewater could be present at concentrations toxic to plants. The wastewater could contain suspended solids that may plug the capillary pores in the soil as well as block nozzles in the water distribution system. Great investment in equipment and land. Regulation, guideline and criteria have been established for the reuse of wastewater for agriculture and are normally based on several parameters, such as public health protection and concentration of components in the water. These components include salinity, boron, exchangeable ions and trace metals are of particular important. Table 2.2 presents the details of guidelines for water quality to be used for agricultural irrigation. These guidelines are established by the Food and Agricultural Organization in United Nation. I. Salinity As indicated, salinity is the most influential parameter in determining the applicability of water for agricultural irrigation. Salinity refers to the presence of dissolved salts in the soil and water. Table 2.2 Guidelines for Interpretation of Water Quality for Irrigation Degree of restriction on use Potential irrigation problemUnitsNoneSlight to moderate Severe Salinity (affects crop water availability)a ECdS/m0.70.7-3.0 3.0 or, TDSmg/L450450-2000 2000 Infiltration (affects infiltration rate of water into the soil. Evaluation using EC and SAR together)b SAR= 0-3and EC =0.70.7-0.2 0.2 = 3-6and EC =1.21.2-0.3 0.3 = 6-12and EC =1.91.9-0.5 0.5 = 12-20and EC =2.92.9-1.3 1.3 = 20-40and EC =5.05.0-2.9 2.9 Specific ion toxicity (affects sensitive crops) Sodium (Na)b Surface irrigationSAR33-9 9 Sprinkler irrigationmg/L33 Chloride (Cl)c Surface irrigationmg/L44-10 10 Sprinkler irrigationmg/L33 Boron (B)mg/L0.70.7-3.0 3.0 Trace elements (See Table) Miscellaneous effects (affects susceptible crops) Nitrogen (NO3-N)dmg/L55-30 30 Bicarbonate (HCO3) (overhead sprinkling only)mg/L1.51.5-8.5 8.5 pHNormal range6.5-8.4 a EC = electrical conductivity, a measure of water salinity, report in deciSiemens per meter at 25 °C (dS/m) or in units millimhos per centimeter (mmho/cm). Both are equivalent. TDS = total dissolved solids, report in milligram/liter (mg/L). b SAR = sodium adsorption ratio. At a given SAR, infiltration rate increases as water salinity increases. Evaluate the potential infiltration problem by SAR as modified by EC. c For surface irrigation, most tree crops and woody plants are sensitive to sodium and chloride; use the values shown. Most annual crops are not sensitive. With overhead sprinkler irrigation and low humidity (30%) sodium and chloride may be absorbed through the leaves of sensitive crops. d NO3-N, nitrate nitrogen, reported in terms of elemental nitrogen (NH4-N and organic-N should be included when wastewater is being tested). From Ayers, R.S. and Westcot, D.W., FAO, 7, 11, 54, 69, 1976. There are two assessments that characterize the salinity of water involving measuring total dissolved solids and electrical conductivity. Total dissolved solids refers to the material left in a vessel after evaporation of a filtered water sample and subsequent placed in a drying oven at a defined temperature.6 The total dissolved solids concentration relates to the conductivity of the water. The total dissolved solid can be calculated by multiplying conductivity by a factor, but the factor is not a constant. A factor most often used in agricultural is 640. TDS (mg/L) = EC (mmho/cm or dS/m) ? 640 Electrical conductivity is other measurement that more useful than total dissolved solids because it can be made easily and instantaneously by irrigators in the field. Salts that are dissolved in water conduct electricity. Therefore, the salt in the water is related to the electrical conductivity. Table 2.3 presents general guidelines as to the salinity hazard, total dissolved solids (TDS) and electrical conductivity. Table 2.3 General Guidelines for Salinity in Agricultural Irrigation Watera Classificationb TDS (mg/L) EC (mmhos/cm)c Water for which no detrimental effects are usually noticed500 0.75 Water that can have detrimental effects on sensitive crops500-1000 0.75-1.50 Water that can have adverse effects on many crops, requiring careful management practices1000-2000 1.50-3.00 Water that can be used for tolerant plants on permeable soils with careful management practices2000-5000 3.00-7.50 a Normally only of concern in arid and semiarid parts of the country. b Crops vary greatly in their tolerance to salinity (TDS or EC). c EC = electrical conductivity. Adapted from USEPA, Office of Water Program Operations, EPA-430/9-75-001, 1975. The adverse impacts of salinity can be augmented by a soil with poor characteristics (such as high evapotranspiration rates and poor drainage) that can indirectly affect the crop. The only way to control salinity hazard is by applying more water that carries off excess salt and leaches throughout the plant’s root zone. II. Exchangeable Cations The concentration of exchangeable cations in irrigation water must be considered. The exchangeable cations include sodium, calcium and magnesium. When sodium concentrations are high, the soil permeability is reduced and the soil structure is affected. When calcium is normally the predominant exchangeable cation in soil, the soil tends to have a granular structure which is easily worked and readily permeable. The sodium adsorption ratio has been developed to assess the degree to which sodium in irrigation water and provide an indicator of its potential deleterious effects on soil structure and permeability. The sodium adsorption ratio (SAR) of water is defined to the equation below: where: Na+= sodium Ca2+ = calcium Mg2+ = magnesium For irrigation water containing significant values of bicarbonate, the adjusted sodium adsorption ratio is sometimes used. The equation of adjusted sodium adsorption ratio (SARadj) is defined as follow: where: pK’2 – pK’c = empirical constants p (Ca2+ + Mg2+) = negative logarithm of the calcium and magnesium ion concentration in moles/liter p (ALK)= negative logarithm of the total alkalinity in milliequivalents/liter For general crops, the tolerance value of SAR and adjusted SAR for irrigation water is 8 to 18. In fact, the calculated SAR values in the range are suitable for sensitive crops. III. Boron Boron in treated wastewater is a potential hazardous ion for agricultural irrigation at high concentrations of around 1mg/L. The sources of boron in wastewater are normally from household detergents, industrial plants and sewage system where boron fertilizers are used. However, it must be remembered that boron is essential in crop productivity at low concentrations. Boron is also one of the important micronutrients for crops to obtain a high quality and quantity crop yield. As indicated, the deleterious effects for boron can happen on crop. Such effects are dependent on crop sensitivity to boron and boron concentrations in soil. A number of crops have been tested by experiment for boron sensitivity. The boron sensitivity of selected crops is listed in Table 2.4. Table 2.4 Relative Tolerance of Crops and Ornamentals to Boron TolerantSemitolerantSensitive (4.0 mg/L of Boron)(2.0 mg/L of Boron)(1.0 mg/L of Boron) AthelSunflower, nativePecan AsparagusPotatoWalnut, black and Persian or English PalmCotton, Acala and PinaJerusalem artichoke Date palmTomatoNavy bean SugarbeetSweetpeaAmerican elm MangelRadishPlum Garden beetField peaPear AlfafaRagged-robin roseApple GladilsOliveGrape (Sultanina andMalaga) BroadbeanBarleyKadota fig OnionWheatPersimmon TurnipCornCherry CabbageMiloPeach LettuceOatApricot CarrotZinniaThornless blackberry PumpkinOrange Bell pepperAvocado Sweet potatoGrapefruit Lima beanLemon (2.0 mg/L of boron)(1.0 mg/L of boron)(0.3 mg/L of boron) Note:Relative tolerance is based on the boron concentration in irrigation water at which boron toxicity symptoms were observed when plants were grown in sand culture. It does not necessarily indicate a reduction in yield. Tolerance decreases in descending order in each column. From Ayers, R.S. and Westcot, D.W., FAO, 7, 11, 54, 69, 1976. In United Nations, the Food and Agricultural organization issued guidelines for boron concentrations in irrigation water. The guidelines indicate that no issues will occur will occur for crops at boron concentration less than 0.75 mg/L. Between 0.75 and 2.0 mg/L of boron concentrations, increasing problem will exist, and severe problem happen at boron concentration above 2.0 mg/L. Table 2.5 presents the detailed guidelines for the allowable concentration of boron in treated wastewater for agricultural irrigation. Table 2.5 Limits of Boron in Irrigation Water Permissible Limits (Boron in miligrams per liter or parts per million) Crop Group Class of waterSensitiveSemitolerantTolerant Excellent0.330.671.0 Good0.33-0.670.67-1.331.0-2.0 Permissible0.67-1.01.33-2.02.0-3.0 Doubtful1.0-1.252.0-2.53.0-3.75 Unsuitable1.252.53.75 From van der Leeden, F., Troise, F.L., and Todd, D.K., The Water Encyclopedia, 2nd ed., Lewis Publishers, Boca Raton, FL, 1990, 466. Wastewater treatment systems are not efficient at removing boron unless some form of treatment is carried out, such as chemical precipitation. Some management options can also be adopted to degrade the toxicity of boron in treated wastewater and improve yields. These management options are engineered to provide additional nitrogen to maximize fertility of the soil. IV. Trace Metals or Elements All wastewater sent to treatment plants contain trace elements. The source of trace element is usually from industrial plant, but wastewater from residences can also have high trace element concentrations. Trace elements normally occur in treated wastewater but at very low concentrations, usually less than a few milligrams per liter with most less than 100 micrograms per liter. Some trace elements are essential for plant and animal growth at low concentrations, but all can exhibit plant toxicity at elevated concentration. The essential trace elements in wastewater include cadmium, chromium, copper, lead, mercury, molybdenum, nickel and zinc.7, 8, 9 The concentrations of trace elements in treated wastewater vary with wastewater treatment processes provided and their sources. Typically, the concentrations of trace elements in treated wastewater are in the range where negative effects are not likely to happen in short term. However, long term application of treated wastewater containing trace elements may lead to accumulation of trace elements in soil and may potentially result in groundwater contamination and plant toxicity. The range and recommended maximum concentrations of the trace elements in treated wastewater for agricultural irrigation are presented in Table 2.6. Table 2.6 Recommended Limits for Constituents in Reclaimed Water for Irrigation7 Long-Term UseShort-Term Use Constituent(mg/L) (mg/L) Remarks Trace Heavy Metals Aluminium5.0 20.0 Can cause nonproductivity in acid soils, but soils at pH 5.5 to 8.0 will precipitate the ion and eliminate toxicity. Arsenic0.10 2.0 Toxicity to plants varies widely, ranging from 12 mg/L forSudangrass to less than 0.05 mg/L for rice. Beryllium0.10 0.5 Toxicity to plants varies widely, ranging from 5 mg/L for kale to 0.5 mg/L for bush beans. Boron0.75 2.0 Essential to plant growth, with optimum yields for many obtained at a few-tenths mg/L in nutrient solutions. Toxic to many sensitive plants (e.g., citrus) at 1 mg/L. Usually sufficient quantities in reclaimed water to correct soil deficiencies. Most grasses relatively tolerant at 2.0 to 10 mg/L. Cadmium0.01 0.05 Toxic to beans, beets, and turnips at concentrations as low as 0.1 mg/L in nutrient solution. Conservative limits recommended. Chromium0.1 1.0 Not generally recognized as essential growth element. Conservative limits recommended due to lack of knowledge on toxicity to plants. Cobalt0.05 5.0 Toxic to tomato plants at 0.1 mg/L in nutrient solution. Tends to be inactivated by neutral and alkaline soils. Copper0.2 5.0 Toxic to a number of plants at 0.1 to 1.0 mg/L in nutrient solution. Fluoride1.0 15.0 Inactivated by neutral and alkaline soils. Iron5.0 20.0 Not toxic to plants in aerated soils, but can contribute to soil acidification and loss of essential phosphorus and molybdenum. Lead5.0 10.0 Can inhibit plant cell growth at very high concentrations. Lithium2.5 2.5 Tolerated by most crops at up to 5 mg/L; mobile in soil. Toxic at citrus at low doses – recommended limit is 0.075 mg/L. Table 2.6 (continued) Recommended Limits for Constituents in Reclaimed Water for Irrigation Long-Term UseShort-Term Use Constituent(mg/L) (mg/L)Remarks Trace Heavy Metals Manganese0.2 10 Toxic to a number of crops at a few-tenths to a few mg/L in acid soils. Molybdenum0.01 0.05 Nontoxic to plants at normal concentrations in soil and water. Can be toxic to livestock if forage is grown in soils with high levels of available molybdenum. Nickel0.2 2 Toxic to a number of plants at 0.5 to 1.0 mg/L; reduced toxicity at neutral or alkaline pH. Selenium0.02 0.02 Toxic to plants at low concentrations and to livestock if forage is grown in soils with low levels of added selenium. Tin, Tungsten, Titanium2 2 Effectively excluded by plants; specific tolerance levels unknown. Vanadium0.1 1 Toxic to many plants at relatively low concentrations. Zinc2 10 Toxic to many plants at widely varying concentrations; reduced toxicity at increased pH (6 or above) and in fine-textured or organic soils. Other Parameters ConstituentRecommended Limit Remarks pH6 Most effects of pH on plant growth are indirect (e.g., pH effects on heavy metals’ toxicity described above). TDS500-2000 mg/L Below 500mg/L, no detrimental effects are usually noticed. Between 500 and 1000 mg/L, TDS in irrigation water can affect many crops and careful management practices should be followed. Above 2000 mg/L, water can be used regularly only for tolerant plants on permeable soils. Free Chlorine Residual1 mg/L The secondary treatment processes vary in their effectiveness at the removal of significant trace elements. However, advance treatment process such as carbon adsorption and chemical coagulation can remove over 90 percent of the trace elements from the wastewater. As indicated, some trace elements are toxic at elevated concentrations. Cadmium, copper and molybdenum can be hazardous to animals at concentration too low to affect crops. Cadmium is of special concern as it can accumulate in the food chain. It does not affect ruminants in the little amounts they ingest. Most beef and milk products are unaffected by livestock ingestion of cadmium as it is stored in the kidneys and liver of the animal rather than the muscle tissues or fat. Copper is not harmful to monogastric animals but can be toxic to ruminants. However, the animal’s tolerance to copper increases as available molybdenum increases. Molybdenum may also be hazardous when available in the absence of copper. While zinc and nickel are a lesser concern than cadmium, copper and molybdenum. They have negative effects on plants at lower concentrations than the levels harmful to plants and animals. However, zinc and nickel toxicities are decreased as the pH is increased. 2.2.2 Wastewater Reuse for Industrial Use Treated wastewater can be an important potential source of water for many industries, particularly in water-short regions. The quantity of water used in power generation and manufacturing processes is very large and the availability of unlimited of water was considered as a prerequisite. Wastewater reuse for industrial use has many potential applications, ranging from common housekeeping options to advanced technology implementation. The reuse of wastewater for industry can be adopted through industrial processes, internal recycling and non- industrial reuse of industrial facility effluent. The major industrial categories that use treated wastewater include:7 Evaporative cooling water, Boiler feedwater, Process water, and Irrigation and maintenance of plant grounds, fire protection, and dust control. Among the various industrial users of treated wastewater, cooling water is the greatest single application. All heat from various industrial processes must be removed and the most efficient coolant is water. The water can be a once-through recirculating cooling system or cascading use of cooling water in other applications. Water quality requirements for industrial applications are related to four different issues include scaling, corrosion, biological growth and fouling, which may affect industrial process efficacy and integrity, as well as product quality. These concerns are addressed by the options summarized in Table 2.7. Table 2.7 Industrial Water Reuse: Concerns, Causes, and Treatment Options ConcernsCausesTreatment options Scalinginorganic compounds,saltsscaling inhibitor, carbon adsorption, filtration, ion exchange,blowdown rate control Corrosiondissolved and suspended solids pH imbalancecorrosion inhibitor,reverse osmosis Biological growthresidual organics, ammonia, phosphorousbiocides, dispersants, filtration Foulingmicrobial growth, phosphates, dissolved and suspended solidscontrol of scaling, corrosion, microbial growth, filtrationchemical and physical dispersants From Asano and Levine, 1998. Pathogens in treated wastewater used in industrial applications present potential health risks to workers and public from aerosols and windblown spray. Aerosols contain toxic organic compounds and bacteria, such as Legionella pneumophila, which causes Legionnaire’s disease. In recent years, the net quantity of water used has reduced sharply because water shortages and discharge regulations have made it necessary to treat it before disposing it away. A large quantity of this reduction is achieved by internal reuse. 2.2.3Wastewater Reuse for Recreational Use The treated wastewater may serve a variety of recreational applications include swimming, boating and fishing. The appearance of treated wastewater is essential when it is used, and treatment for nutrient removal may be adopted. Without nutrient control, there is a potential issue for algae blooms, resulting in odors and eutrophic conditions. The criteria, regulations and guidelines of treated wastewater for recreational purposes will vary with the potential for human contact, as well as the sources of the secondary pollutants, such as body discharges, air contaminants and sewage. The criteria, regulations and guidelines of treated wastewater to be used for recreational applications can be subdivided into the following three groups. I. Elementary Body Contact Recreational Water This group of treated wastewater used in situations where there is intimate contact between the human body and the water and where there is a potential risk of ingesting a large amount of water which may pose a health risk. The treated wastewater used for contact recreational purposes include swimming, waterskiing, bathing, etc. The methods of transmission of virus may happen due to ingestion of water or via the exposed mucous membranes and skin in protective ski barrier. Swimming pools have been implicated as the adenovirus pharyngitis and conjunctivitis, as well as enterovirus meningitis.10 Some of the diseases transmitted by swimming pool water are listed in Table 2.8. Table 2.8 Some Diseases Transmitted by Swimming Pool Water DiseaseCausative agent ConjunctivitisVirus Sinusitis and otitisStreptococci and Staphylococci (propagated by nasal mucus) Certain types of enteritisSome pathogens or certain viruses ingested with water Skin disease: EczemasKoch bacillus GranulomaMycobacterium marinum EpidermophytosisBrought about by the fungus that attaches itself to the skin between the toes and is contracted particularly easily when walking on areas around the pool. Typhoid feverSalmonella typhi DysenteryEntamoeba histolytica, Shigella Infectious hepatitisVirus Compiled from Reference 10 and 11. Normally, the criteria, regulations and guidelines of treated wastewater used that are adopted for this group are more stringent. For use in recreational applications where full body contact with the water is permitted, the water should be colorless, microbiologically safe and non-irritating eyes or skin. II. Secondary Body Contact Recreational Water This group of treated wastewater used includes fishing, boating, canoeing, camping, and golf course and landscape irrigation. Treated wastewater used for this category should not contain high levels of heavy metals or pathogens that accumulate in fish to degrees that pose health threat to the consumers. The recommended water quality criteria for body contact and secondary body contact are presented in Table 2.9. References 1Committee to Evaluate the Viability of Augmenting Potable Water Supplies with Reclaimed Water, Water Science and Technology Board, Commission on Geosciences, Environment, and Resources, National Research Council, Issues in Potable Reuse: The Viability of Augmenting Drinking Water Supplies with Reclaimed Water, National Academy Press, Washington, D.C., 1998. 2Takashi Asano, Wastewater Reclamation and Reuse, Technomic Pub.,Lancaster,Pa., 1998. 3 Donald R. Rowe, Isam Mohammed Abdel-Magid, Handbook of Wastewater Reclamation and Reuse, Lewis Pub., Boca Raton, Fla., 1995. 4 Shuval, H. I., Water Renovation and Reuse, Academic Press,New York, 1977. 5 Rowe, D. R., K. Al-Dhowalia, and A. Whitehead, Reuse of Riyadh Treated Wastewater, Project No. 18/1402, King Saud University, The College of Engineering Research Center, Riyadh, Saudi Arabia, 1988. 6 USPHA, Standard Methods for the Examination of Water and Wastewater, 15th ed., American Public Health Association,Washington,D.C., 1980. 7 USEPA, Manual – Guidelines For Water Reuse, EPA/625/R-92/004, Office of Water, Office of Wastewater Enforcement and Compliance, U.S. Environmental Protection Agency, Washington, D.C., September, 1992. 8Ayers, R. S. and D. W. Westcot, Water Quality for Agriculture, Food and Agriculture Organization of the United Nations,Rome, 1976. 9USEPA, Process Design Manual for Land Treatment of Municipal Wastewater, EPA 625/1-77-008, E1, E2 U.S. Environmental Protection Agency, Washington, D.C., October, 1977. 10 WHO, Report of a WHO Scientific Group, Human Viruses in Water, Wastewater and Soil, TRS 639, WHO, Geneva, 1979. 11 Glossary Water and Wastewater Control Engineering, 3rd ed., American Public Health Association,Washington,D.C., 1981. How to cite Wastewater reuse growing unprecedented populations and increasing pressure., Essay examples

Distribution Strategy free essay sample

In marketing, it is impossible to avoid consideration of marketing mix, which involves 4Ps. The 4Ps encompass: place, promotion, price and product (Viardot, 2004). This exposes one of crucial obligations of any marketing manager. That is, a marketing manager is responsible for formulating effective distribution strategy (place) in order to keep the other Ps moving (Distributionstrategy. org. , 2013). As a result, studies described distribution strategy as crucial prerequisite for success of any business (Chapter 15: Product Distribution, n. d. ). It is a plan of actions employed to move service/product from the manufacturer to the end consumers through different approaches such as physical distribution and distribution channels. Generally, it tries to describe where and how customers purchase firm’s service/products. Distribution strategy focuses on various factors, which encompass: location of the firm and target market, approaches of reaching the target market, warehousing, as well as transportation. In this paper, distribution strategy critically discussed besides evaluating how it used in consumer market. Channel intermediaries are firms or individuals such as wholesalers, agents, brokers, or retailers who help move a product from the producer to the consumer or business user. A company’s channel decisions directly affect every other marketing decision. Place decisions, for example, affect pricing. Marketers that distribute products through mass merchandisers such as Wal-Mart will have different pricing objectives and strategies than will those that sell to specialty stores. Distribution decisions can sometimes give a product a distinct position in the market.The choice of retailers and other intermediaries is strongly tied to the product itself. Manufacturers select mass merchandisers to sell middle price ranged products while they distribute top-of-the-line products through high-end department and specialty stores. The firm’s sales force and communications decisions depend on how much persuasion, training, motivation, and support its channel partners need. Whether a company develops or acquires certain new products may depend on how well those products fit the capabilities of its channel members. Some companies pay too little attention to their distribution channels.

Autism Essays (2130 words) - Autism, Psychiatric Diagnosis

Autism Autism Throughout the years the diagnosis of autism has changed dramatically. Once, it was mistakenly diagnosed as childhood schizophrenia. Now that much more extensive research has been done, researchers have found distinct characteristics that are typical of autistic individuals. It is most often characterized by difficulty in the child's ability to respond to people, events, and objects. Responses to sensations of light, sound, and feeling may be exaggerated. Delayed speech and language may be associated. Other characteristics include: impairment in ability to make peer friendships, absence of imaginative activity, stereotyped body movements, persistent preoccupation with parts of objects, marked distress over changes in trivial aspects of the environment, unreasonable insistence on following routines in precise detail, a restricted range of interests and a preoccupation with one narrow interest, along with many others. Although certain characteristics are typical of autistic children, the diagnosis is a multidisciplinary effort. The diagnosis requires a team of professionals because of the many unique characteristics and behaviors of the autistic child Each professional is assigned a different behavior to monitor. However, the psychiatrist and the psychologist are mainly responsible for the diagnosis and the psychological evaluations involved. The onset of this condition is usually observed within the first two and a half years. In 1968, the APA referred to autism as a single disorder, and now it is known to be a syndrome of behavioral and medical effects. Along with autism, several related disorders are grouped under Pervasive Developmental Disorders, PDD, a general category which is characterized by severe and pervasive impairment in several areas of development. The standard reference is known as the Diagnostic and Statistical Manual, DSM, which is now in its fourth edition. The DSM classifies the different types of PDD which are often mistaken as autism. The other PDD are Asperger's Disorder, Rett's Disorder, Childhood Disintegrative Disorder, and Pervasive Developmental Disorder-Not Otherwise Specified, PDD-NOS, which is commonly referred to as atypical autism. The term autistic spectrum disorder is frequently used to acknowledge the diversity and severity of autism . The characteristics and symptoms of autism can present themselves in a wide variety of combinations. There is no standard type and no suc h thing as a typical person with autism. The most commonly used terms to describe people with autism are: autistic-like, autistic tendencies, autistic spectrum, high functioning, or low functioning, and more-abled or less-abled. Autistic disorder is also know as Infantile Autism or Kanner's Syndrome. Most children with this condition exhibit poor social skills, and impaired cognitive functioning and language. What is it that causes this national crisis, affecting over 400,000 families, and costing the nation over 13 billion dollars. Autism is the third most common developmental disorder, more common than Down Syndrome, multiple sclerosis, or cystic fibrosis, and autism research still receives less than 5% of the funding of the other diseases. With the lack of funding, researchers from all over the world are spending a considerable amount of time and energy trying to find answers. A single specific cause of autism is still not known. The most current research links autism to neurological or biological differences in the brain, and in many families a pattern of autism or autism related disabilities appears. This could suggest that autism has a genetic basis, although no specific gene has been directly linked t o autism. Researchers believe that a genetic basis would be highly complex, involving a combination of several genes. Direct causes have not been discovered, but several theories has been proven false. Autism is not a mental disorder, children with autism are not unruly kids who choose not to behave. Autism is not caused by bad parenting, and no known psychological factors in child development have been proven to cause autism. Children with autism begin to show signs of this disease at around the age of two. This is when parents may notice delays in language, play, or social interaction. One of the many problems autistic children have is with social detachment and unresponsiveness. Autistic babies do not smile at there parents or reach out to be cuddled or picked up. They often do not play with other children, appearing to be in there their own world, unaware of people or events around them. Many children

Laura Clay, Southern Womens Suffrage Leader

Laura Clay, Southern Womens Suffrage Leader Laura Clay Facts Known for: major Southern woman suffrage spokesperson. Clay, like many Southern suffragists, saw womens suffrage as reinforcing white supremacy and power.Occupation: reformerDates: February 9, 1849 - June 29, 1941 Laura Clay Biography Laura Clay Quote: Suffrage is Gods cause, and God leads our plans. Laura Clays mother was Mary Jane Warfield Clay, from a wealthy family prominent in Kentucky horse racing and breeding, herself an advocate of womens education and womens rights. Her father was the noted Kentucky politician Cassius Marcellus Clay, a cousin of Henry Clay, who founded an anti-slavery newspaper and helped found the Republican party. Cassius Marcellus Clay was the United States ambassador to Russia for 8 years under Presidents Abraham Lincoln, Andrew Johnson and Ulysses S. Grant. He returned from Russia for a time and is credited with talking Lincoln into signing the Emancipation Proclamation. Laura Clay had five brothers and sisters; she was the youngest. Her older sisters were involved in working for womens rights. Mary B. Clay, one of her older sisters, organized Kentuckys first womens suffrage organization, and was president of the American Woman Suffrage Association from 1883 to 1884. Laura Clay was born at her familys home, White Hall, in Kentucky, in 1849. She was the youngest of four girls and two boys. Lauras mother, Mary Jane Clay, was largely in charge, during her husbands long absences, of managing the family farms and property inherited from her family. She saw that her daughters were educated. Cassius Marcellus Clay was from a wealthy slaveholding family. He became an anti-slavery advocate, and among other incidents where he was met with violent reactions to his ideas, he was once nearly assassinated for his views. He lost his seat in the Kentucky state House because of his abolitionist views. He was a supporter of the new Republican Party, and nearly became Abraham Lincolns vice president, losing that spot to Hannibal Hamlin. At the beginning of the Civil War, Cassius Clay helped organize volunteers to protect the White House from a Confederate takeover, when there were no federal troops in the city. During the years of the Civil War, Laura Clay attended Sayre Female Institute in Lexington, Kentucky. She attended a finishing school in New York before returning to her family home. Her father opposed to her further education. The Reality of Womens Rights From 1865 to 1869, Laura Clay helped her mother run the farms, her father still absent as ambassador to Russia. In 1869, her father returned from Russia and the next year, he moved his four-year-old Russian son into the family home at White Hall, his son from a long affair with a prima ballerina with the Russian ballet. Mary Jane Clay moved to Lexington, and Cassius sued her for divorce on grounds of abandonment, and won. (Years later, he created more scandal when he married a 15 year old servant, probably against her will as he had to restrain her from leaving. He divorced her after she attempted suicide. That marriage ended in divorce just three years later.) Under existing Kentucky laws, he could have claimed all the property his ex-wife had inherited from her family and he could have kept her from the children; he claimed his wife owed him $80,000 for her years living at White Hall. Fortunately for Mary Jane Clay, he did not pursue those claims. Mary Jane Clay and her daughters who were still unmarried lived on the farms she inherited from her family, and were supported by the income from these. But they were aware the under the existing laws, they were able to do so only because Cassius Clay did not pursue his rights to the property and income. Laura Clay managed to attend one year of college at the University of Michigan and one semester at State College of Kentucky, leaving to put her efforts into working for womens rights. Working for Womens Rights in the South Laura Clay Quote: Nothing is so laborsaving as a vote, properly applied. In 1888, the Kentucky Woman Suffrage Association was organized, and Laura Clay was elected its first president. She remained president until 1912, by which time the name had changed to the Kentucky Equal Suffrage Association. Her cousin, Madeleine McDowell Breckinridge, succeeded her as president. As head of the Kentucky Equal Suffrage Association, she led efforts to change Kentucky laws to protect married womens property rights, inspired by the situation in which her mother had been left by her divorce. The organization also worked to have female doctors on staff at state mental hospitals, and to have women admitted to State College of Kentucky (Transylvania University) and Central University. Laura Clay was also a member of the Womens Christian Temperance Union (WCTU) and she was part of the Womans Club movement, holding state offices in each organization. While Laura Clays father had been a liberal Republican and perhaps in reaction to that Laura Clay became active in Democratic Party politics. Elected to the board of the National American Woman Suffrage Association (NAWSA), newly merged in 1890, Clay chaired the new groups membership committee and was its first auditor. Federal or State Suffrage? Around 1910, Clay and other Southern suffragists began to be uncomfortable with efforts within the national leadership to support a federal woman suffrage amendment. This, they feared, would provide a precedent for federal interference in the voting laws of Southern states which discriminated against African Americans. Clay was among those who argued against the strategy of a federal amendment. Laura Clay was defeated in her bid for reelection to the board of the NAWSA in 1911. In 1913, Laura Clay and other Southern suffragists created their own organization, the Southern States Woman Suffrage Conference, to work for state-level womens suffrage amendments, to support voting rights only for white women. Probably hoping for compromise, she supported federal legislation to allow women to vote for members of Congress, providing the women otherwise qualified as voters in their states. This proposal was debated at NAWSA in 1914, and a bill to implement this idea was introduced into Congress in 1914, but it died in committee. In 1915-1917, like many of those involved in womens suffrage and womens rights, including Jane Addams and Carrie Chapman Catt, Laura Clay was involved in the Womans Peace Party. When the United States entered World War I, she left the Peace Party. In 1918, she briefly joined in supporting a federal amendment, when President Wilson, a Democrat, endorsed it. But then Clay resigned her membership in the NAWSA in 1919. She also resigned from the Kentucky Equal Rights Association that she had headed from 1888 to 1912. She and others formed, instead, a Kentucky-based Citizens Committee to work for a suffrage amendment to the Kentucky state constitution. In 1920, Laura Clay went to Nashville, Tennessee, to oppose ratification of the woman suffrage amendment. When it (barely) passed, she expressed her disappointment. Democratic Party Politics Laura Clay Quote: I am a Jeffersonian Democrat. In 1920, Laura Clay founded the Democratic Womens Club of Kentucky. That same year was a delegate to the Democratic National Convention. Her name was placed in nomination for President, making her the first woman so nominated at a major partys convention. She was nominated in 1923 as a Democratic candidate for the Kentucky State Senate. In 1928, she campaigned in Al Smiths presidential race. She worked after 1920 for repeal of the 18th Amendment (prohibition), even though she herself was a teetotaler and a WCTU member. She was a member of the Kentucky state convention that ratified repeal of prohibition (the 21st Amendment), primarily on states rights grounds. After 1930 After 1930, Laura Clay led mostly a private life, focusing on reform within the Episcopal church, her lifelong religious affiliation. She interrupted her privacy to oppose a law paying male teachers more than female teachers would be paid. She worked mostly within the church on womens rights, especially on allowing women to be delegates to church councils, and on permitting women to attend the Episcopal churchs University of the South. Laura Clay died in Lexington in 1941. The family home, White Hall, is a Kentucky historical site today. Laura Clays Positions Laura Clay supported womens equal rights to education and to the vote. At the same time, she believed that black citizens were not yet developed enough to vote. She did support, in principle, educated women of all races getting the vote, and spoke at times against ignorant white voters. She contributed to an African American church project aimed at self-improvement. But she also supported states rights, supported the idea of white superiority, and feared federal interference in Southern states voting laws, and so, except briefly, did not support a federal amendment for woman suffrage. Connections The boxer Muhammed Ali, born Cassius Marcellus Clay, was named for his father who was named for Laura Clays father. Books About Laura Clay Paul E. Fuller. Laura Clay and the Womans Rights Movement 1975.John M. Murphy. Laura Clay (1894-1941), a Southern Voice for Womans Rights. Women Public Speakers in the United States, 1800-1925: A Bio-Critical Sourcebook. Karlyn Kohrs Campbell, ed. 1993.

Early Sunday Morning by Edward Hopper Essay Example | Topics and Well Written Essays - 1250 words

Early Sunday Morning by Edward Hopper - Essay Example In the painting, the sky is clearly seen with no clouds in sight, just a little white fuzz at the right. The shadows being cast by objects indicate the sun is rising from the right side. The streets are empty with only a fire hydrant and a barber’s post appearing at the front of the shops. None of the shops are open too indicating that Edward was taking a walk quite early in the morning. The building in view is a two story building expanding across the length of the street. It seems to have residences at the top and shops at the bottom. The residences are brick red with rectangular windows both open and closed. In the windows are curtains. Some are white, while others are yellow. The shops are a darker green with large windows. Accesses to the residences are not shown. As the building ends towards the right, Edward cuts off the window at the top and the shop’s window. He intended to show that the building was still continuing. This may be true for both sides. On the top right, there is a dark shadow cast by a taller building. This may have been a newer structure and not part of the original building. It looks greatly out of place. Given the fact that the painting was painted during the time in small towns were being replaced by big cities with taller looming structures, this brings that reality to the painting. The darkness in that section is a sort of foreshadow of what will eventually happen to the small street, be replaced by taller buildings. The colours used in the painting also help in making the painting.

Western Civilization of the French Revolution Essay

Western Civilization of the French Revolution - Essay Example It essentially detailed his life, including capture, slavery, brutality, and eventual literacy. It was created in the United Kingdom. It is useful to historians because it provides a first-hand account of slavery, something that is relatively hard to come by, as so few were literate. The French Revolution was one of the most turbulent times in western history – it involved mass uprisings, huge reversals in power and wealth, and had one of the strangest endings: the rise of Napoleon. The development of one of the world’s most famous late emperors is a strange ending to a democratic revolution. Some argue that Napoleon largely upheld revolutionary values during his reign – and indeed there are some ways this was true, such as installing a civil code of laws to replace the whims of rulers, aristocrats and so forth and would eventually be a major influence in many countries around the world. However, this and similar achievements cannot overshadow the fact that the fundamentals of the revolution were populist, and an emperorship is anything but. If the spirit of the revolution was enshrined in the phrase â€Å"Libertà ©, Égalità ©, Fraternità ©,† then it is clear Napoleon did not live up to those standards. As mentioned previously, it is tempting to argue that Napoleon upheld many aspects of the revolution. Certainly his reign was nothing like as terrible to the French populace as that of the monarchs that proceeded the revolution: the economy was largely stabilized, wealth was less concentrated in the hands of the wealthy than previously and so forth. His Civil Code embodied many of the features present in the declaration of the rights of man,1 especially in imagining the rule of law as the prime mechanism of power, replacing the absolute control held by previous monarchs. While these achievements should be

Ammonium Dihydrogen Phosphate (ADP) Crystals Structure

Ammonium Dihydrogen Phosphate (ADP) Crystals Structure Ammonium dihydrogen phosphate (ADP) crystals are widely used as the second, third and fourth harmonic generator for Nd:YAG and Nd:YLF lasers. It belongs to the tetragonal system with the space group I-42d 1. These crystals are widely used for electro-optical applications such as Q-switching for Ti–sapphire and alexandrite lasers as well as for acousto optical applications2–4. Tris(thiourea)zinc(II) sulphate (ZTS) is a semi-organic nonlinear optical (NLO) material which finds applications in the area of laser technology, optical communication, data storage technology and optical computing because it has high resistance to laser induced damage, high nonlinearity, wide transparency, low angular sensitivity and good mechanical hardness compared to many organic NLO crystals5-8. It belongs to the orthorhombic system with noncentrosymmetric space group Pca21 and point group mm2. Growth, spectral, optical and thermal studies of rare earth neodymium(III) doped ZTS9, cerium(III) doped ZTS10,11 have been reported. We have also investigated the influence of Ce(III)- doping12 effects of ADP crystals. In the present investigation, the effect of La(III)-doping on ADP and ZTS crystals has been studied using FT-IR, XRD, SEM, EDS, UV–vis, thermal and Kurtz powder SHG measurements. ADP (E. Merck) was purified by repeated recrystallization. ZTS was synthesized as reported earlier13. To avoid decomposition, low temperature ( ZnSO4 ·7H2O + 3(CS(NH2)2) à ¯Ã¢â‚¬Å¡Ã‚ ® Zn(CS(NH2)2)3SO4 After successive recrystallization processes, crystals were grown by slow evaporation solution growth technique (pH = 6.2). Doping of lanthanum (5 mol %) in the form of lanthanum(III)- chloride (Aldrich) was used as such in the aqueous growth medium. The crystallization took place within 10–15 days and the high quality transparent crystals were harvested from the aqueous growth medium. Best quality and highly transparent seed crystals are used in the preparation of bulk crystals. Photographs of the as-grown crystals are shown in Fig. 2.2.1. The FT-IR spectra of pure and doped crystals reveal small shifts in some of the characteristic vibrational frequencies (Table.2.3.1.1.) and it could be due to lattice strain as a result of La(III)- doping. The vibrational patterns of lanthanum doped ADP exhibit slight variations as compared with pure ADP. PO4 stretching and bending vibrations are observed at ~1100, ~910 cm-1 and ~453, ~546 cm-1 respectively. Symmetric stretching vibrations of NH4+ ion are observed in the range of ~1407 cm-1. Vibrational peak at ~1280 cm-1 corresponds to OH bending. Broad peaks observed at ~3234 cm-1, ~3120 cm-1 correspond to N–H ·Ã‚ ·Ã‚ ·O stretching vibrations. A close observation of FT-IR spectra of pure ZTS and doped specimens also reveals that the doping results in slight shifts in some of the characteristic vibrational frequencies. It could be due to lattice strain developed as a result of doping. An absorption band in the region 2750–3400 cm-1 corresponds to the symmetric and asymmetric stretching frequencies of NH2 group of zinc(II) coordinated thiourea. The absorption band observed at ~1620 cm-1 in the spectra of pure and doped specimens corresponds to that of thiourea (~1625 cm-1)14 of about the same frequency and it can be assigned to NH2 bending vibration. The CN stretching frequencies of thiourea (1122 and 1502 cm-1) shifted to higher frequencies for pure and La(III)- doped ZTS crystals (~1128 and ~1500 cm-1). The C-S is stretching frequencies (1398 and 712 cm-1)15 are shifted to lower frequencies (~1394 and ~706 cm-1) for pure and doped samples. These observations suggest that metal coordinate with thiourea through The powder XRD patterns of La(III)-doped samples are compared with that of undoped one (Fig. 2.3.2.1). No new peaks or phases were observed by doping with inner transition metal lanthanum. However, a drastic reduction in intensity is observed as a result of doping. The most prominent peaks with maximum intensity of the XRD patterns of pure and doped specimens are quite different. The observations could be attributed to strains in the lattice. The cell parameters are determined from the single crystal X-ray diffraction analysis and the values of pure and doped crystals are given in the Table 2.3.2.1. The ionic radius of the dopant La(III) (117 pm) is very small compared with that of NH4+ (151 pm)16. Hence, it is reasonable to believe that the dopant can enter into the ADP crystalline matrix occupying predominantly substitutional positions without causing much distortion. However, the valance of the dopant is different from the host and hence one cannot expect only the simple substitut ional occupancy leading to inhomogeneous strains in the crystal17. It is also appropriate to mention here that in the case of dopants having a dissimilar valance and size from the substituting element of the host lattice, due to expected strain, even small thermal/ mechanical fluctuations during the growth process lead to easy formation of structural defects18,19. It clearly shows that the crystal undergoes non-uniform strain in the lattice. The cell volume of the La(III)- doped ZTS crystals increased (Table. 2). It could be due to the small ionic radius of Zn2+ (88 pm) in comparison with that of La(III) (117 pm)17. This type of behavior (the unit cell volume of the doped materials not varying regularly with the ionic radius of the dopant) has been explained by the electron-doping effect counteracting the steric effect20. The concentration of absorbing species can be determined using the Kubelka-Munk equation21, The direct and indirect band gap energies obtained from the intercept of the resulting straight line with the energy axis at [F(R)hÃŽ ½]2 = 0 and [F(R)hÃŽ ½]1/2 = 0 are deduced as 5.35 eV and 5.50 eV respectively for ADP:La and 5.37 eV 5.70 eV for ZTS:La (Fig. 2.3.3.1). The effect of the influence of dopant on the surface morphology of ADP crystal faces reveals structure defect centers as seen in SEM images (Fig.2.3.4.1). A plate like morphology with a layered structure is exhibited. The incorporation of lanthanum in the ADP crystal matrix results in cluster of scatter centers and voids than those of the undoped specimen. The flower like morphology is observed in ZTS doped specimens. Pure ZTS contains small defect centers in the plate surface and incorporation of La(III) increases the surface roughness (Fig.2.3.4.1(b)). The incorporation of La(III) into the crystalline matrix was confirmed by EDS performed on ADP and ZTS (Fig.2.3.5.1). It appears that the accommodating capability of the host crystal is limited and only a small quantity is incorporated into the ADP and ZTS crystalline matrix. EDS reveals that the accommodating capability of ZTS is much better than ADP as shown in Fig.2.3.5.1(b). The amount of doping in ADP:La and ZTS:La specimens are estimated using AAS and the foreign metal ion entering into the ADP/ZTS crystal matrix is much smaller but significant. Further, the final dopant concentration within the host lattice is not proportional to the prevailing concentration of dopant in the solution at the time of the crystallization process, since the host crystal can accommodate the dopant only to a limited extent. The AAS data reveal that the La(III) ion concentration in ADP and ZTS crystalline matrix are 7.5 ppm and 11.3 ppm respectively. High incorporation of the dopant takes place in the case of lanthanide doping in ZTS compared to ADP. TG/DTA thermogram reveals the purity of the material. The thermogram curve shows a gradual mass loss and residual mass obtained at 1000 ËÅ ¡C is only 10% Fig.2.3.6.1 (a) An endothermic peak is obtained in the DTA analysis for ADP:La at a higher temperature (200ËÅ ¡C) than the pure ADP crystals (191 ËÅ ¡C). The melting point of the material was confirmed by using Sigma instruments melting point apparatus (200ËÅ ¡C). The investigation shows that there is no physically absorbed water in molecular structure of crystals grown from the solution. The simultaneous TG-DTA curves in nitrogen for ZTS and ZTS:La systems at a heating rate of 20 ËÅ ¡C/min are given in the Fig.2.3.6.1(b). The absence of water of crystallization in the molecular structure is indicated by the absence of weight loss around 100 ËÅ ¡C. The melting point of pure ZTS is 231ËÅ ¡ C. A good thermal stability of ZTS:La is observed up to ~235 ËÅ ¡C and the thermal behavior is not very much altered in the presence of the dopant. The sharp endothermic peak at 235 ËÅ ¡C is may be due to melting point. TG curves show a gradual mass loss and residual mass obtained at 1000 ËÅ ¡C is ~20 %. The sharpness of the peak shows the good degree of crystallinity of the material. No decomposition up to the melting point ensures the stability of the material for application in lasers, where the crystals are required to withstand high temperatures. In order to confirm the influence of doping on the nonlinear optical properties (NLO) of the as-grown crystals, these were subjected to SHG test. The SHG efficiency of the materials was performed by Kurtz powder SHG method22. Input radiation used is 2.5 mV/pulse. The output SHG intensities of La(III) doped ADP and ZTS specimens give relative NLO efficiencies of the measured specimens. The doubling of frequency was confirmed by the green color of the output radiation whose characteristic wavelength is 532 nm and it indicates that the doped material exhibits second order NLO effect. The efficient SHG demands specific molecular alignment of the crystal to be achieved facilitating nonlinearity in the presences of a dopant. Incorporation of La(III) into ADP and ZTS crystalline matrix also enhances the SHG efficiency (Table.2.3.7.1) and hence La(III) is a useful dopant. The efficient SHG demands specific molecular alignment of the crystal facilitating nonlinearity in the presence of dopant or it may be due to the improvement in the crystalline perfection of ADP/ZTS crystals by low level La(III)- doping. The effect of various dopants on the SHG efficiencies of ADP/ZTS has been listed in Table.2.3.7.2. The comparative SHG oscilloscope traces of the powder samples ADP:La (blue) and ZTS:La (red) are displayed in Fig. 2.3.7.1. The influence of La(III) doping on the ADP and ZTS crystal has been systematically studied. The reduction in the intensities observed in the powder XRD patterns and slight shifts in vibrational frequencies in FT-IR indicate minor structural variations in the doped materials. Morphological changes in the doped specimen are observed in the SEM micrographs. The studies indicate that the crystal undergoes lattice stress as a result of doping. Energy dispersive X-ray spectrum reveals the incorporation of La(III)- into the crystalline matrix of ADP/ZTS crystals. AAS studies also confirm the above observations. It is clear that the incorporation of La(III)- is comparatively high in the case of ZTS. The thermal analysis reveals the purity of the material. Enhancement in SHG efficiency is observed in ADP/ZTS as a result of La(III)- doping became of facile charge transfer.