environmental sciences

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Expanding Gaps In Water Supply And Demand Environmental Sciences Essay

The gap between the supply and demand for water is expanding and is posing a threat to human existence. (Hussain et al,2002). Water demands throughout the world currently exceed nature's ability to replenish fresh water. This represents global challenges to our abilities to meet ongoing needs for water suitable for human consumption (Weber, 2002). The growth of human populations and the need to create a sustainable environment for society are two of the driving forces behind worldwide improvements in the provision of adequate wastewater treatment. (De Anda, Shear, 2008).

Every community produces liquid wastes. The liquid waste is essentially the water supply of the community after it has been used in many applications. In general, wastewater comprises of liquid waste generated by households, industry, commercial sources as a result of daily usage, production and consumption activities. The objective is to produce a waste stream and a slod waste or sludge suitable for discharge or reuse back into the environment.

Importance and necessity of WWM nowadays

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When untreated wastewater accumulates, the decomposition of the organic matter it contains will lead to nuisance conditions including the production of malodorous gases and numerous pathogenic microorganisms as well as nutrients which may contain toxic compounds that may be mutagenic or carcinogenic. For these reasons, the immediate and nuisance-free removal pf wastewater from its sources of generation, followed by treatment, reuse, or dispersal into the environment is necessary to protect public health and the environment.

Wastewater Management has great impacts on human health and the environment. It is also useful in the decontamination of infectious waste. Wastewater management is therefore important as it helps in the reduction of toxicity of effluent. Many toxic chemicals are transformed into nontoxic compounds by decomposition, degradation and adsorption as a result of these treatment processes. (Jin Sung Ra, et al; 2006). The treatment plants are designed to treat raw wastewater to produce a liquid effluent of suitable quality that can be disposed to the natural surface waters with minimum impact on human health or the environment. (Hussain et al, 2002). Proper management of wastewater would ease the demand of fresh water and reduce the quantity of wastewater, reaching in positive impacts for the environment and livelihoods.

Wastewater management is moving to include minimizing loss of scarce resources, reducing the use of energy and water, reducing waste generation and enabling the recycling of nutrients. (Lundin et al, 2000).

Characteristics of Wastewater

Though the actual composition of wastewater may differ from community to community, all municipal wastewater contains the following broad groupings of Organic matter, Nutrients (Nitrogen, Phosphorus, and Potassium), Inorganic matter (dissolved minerals), Toxic chemicals and Pathogens.

Wastewater has two characteristics:

Physical Characteristics: These characteristics are concerned with detection of wastewater by using the physical senses: temperature, odor, color, and feel of solid material.

Chemical Characteristics: The chemical characteristics of wastewater include: dissolved oxygen, pH, oxygen demand, toxic material, and nutrients.

Water is characterized in terms of its physical, chemical and biological composition.

The principal constituents of wastewater are:

The suspended solids, biodegradable organics composed principally of proteins, carbohydrates and fats, pathogens which contribute to communicable disease, nutrients, refractory organics, heavy metals and dissolved inorganics.

Hazards associated with WW

Wastewater treatment plant operators are exposed to a variety of hazardous chemical agents contained within the effluents and the reagents used in the wastewater processing or generated during the wastewaters treatment. These chemical agents may cause acute poisoning, chemical accidents (e.g., skin burns, injury to the eyes, etc.) damage to the respiratory system, allergies, dermatitis and chronic diseases. In addition, operators may be injured by slips, trips and falls on wet floors; falls into treatment ponds, pits, clarifiers or vats or splashes of hazardous liquids; they may also suffer cuts and pricks from sharp tools. Furthermore, they are exposed to hazards related to work in confined spaces. Other common hazards include electric shock, explosions, entanglement in moving machinery, etc.

Different operating levels and procedures within WWM

The pre-treatemnt removes materials that can be easily collected for the raw wastewater. The water is screened to remove all large oblects carried in the sewage stream.

The primary treatment consists of temporatily holding the sewage ina basin where heavy solids can settle at the bottom while oil, grease and lighter solids float to the surface. The settled and floating materials are removed and the remaining liquid may be discharged or subjected to secondary treatment. In the primary sedimentation stage, sewage flows through large tanks. The tanks are used to settle sludge while grease and oils rise to the surface and are skimmed off. Primary settling tanks are usually equippes with mechanically driven scrapers that continually drive the collected sludge in the base of the tank where it is pumped to sludge treatment facilities.

The secondary treatmnet removes deissolved and suspended biological matter. Secondary treatment is typically perfomed by microorganisims. This treatemnt is designed to substantially degrade the biological content of the sewage which are derived from human waste, food waste, soaps and detergent. The majority of municipal plants treat the settled sewage liquor using aerobic biological processes. To be effective, the biota require both oxygen and food to live. The bacteria and protozoa consume biodegradable soluble organic contaminants and bind much of the less soluble fractions into floc. A filter removes a small percentage of the suspended organic matter, while the majority of the organic matter undergoes a change of character, only due to the biological oxidation and nitrification taking place in the filter. With this aerobic oxidation and nitrification, the organic solids are converted into coagulated suspended mass, which is heavier and bulkier, and can settle to the bottom of a tank. The effluent of the filter is therefore passed through a sedimentation tank, called a secondary clarifier

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In the tertiary treatment, the treated water is sometimes disinfected chemically or physicaaly prior to discharge . The purpose of tertiary treatment is to provide a final treatment stage to raise the effluent quality before it is discharged to the receiving environment. Sand filtration removes much of the residual suspended matter. The purpose of disinfection in the treatment of wastewater is to substantially reduce the number of microorganisms in the water to be discharged back into the environment.

The sludges accumulated in a wastewater treatment process must be treated and disposed of in a safe and effective manner. The purpose of digestion is to reduce the amount of organic matter and the number of disease-causing microorganisms present in the solids.

Anaerobic digestion is a bacterial process that is carried out in the absence of oxygen. The process can either be thermophilic digestion, in which sludge is fermented in tanks at a temperature of 55°C, or mesophilic, at a temperature of around 36°C. One major feature of anaerobic digestion is the production of biogas (with the most useful component being methane), which can be used in generators for electricity production and/or in boilers for heating purposes.

Aerobic digestion is a bacterial process occurring in the presence of oxygen. Under aerobic conditions, bacteria rapidly consume organic matter and convert it into carbon dioxide

Sludge disposal

When a liquid sludge is produced, further treatment may be required to make it suitable for final disposal. Typically, sludges are thickened (dewatered) to reduce the volumes transported off-site for disposal

The removed fluid, called centrate, is typically reintroduced into the wastewater process. The product which is left is called "cake" and that is picked up by companies which turn it into fertilizer pellets.

Health and Safety aspects related to treatment plants

Sewage treatment plant safety is of grave concern around the world due to its unique nature. Sewage treatment plants workers are exposed to a wide variety of hazardous chemicals, deadly confined spaces, explosions, infectious diseases, extremes of heat and cold, along with sprains, cuts and bruises. Some chemically-related health complaints are acute in nature, involving short-term exposure and complaints such as irritations of the eyes, nose or throat. Other problems are chronic in which repeated exposure, sometimes over several years, have affected internal organs or have involved occupationally-related allergies [2]. A single sewage treatment plant may service a hundred or more industries; therefore an enormous range of chemicals may be present in the influent and sludge. The presence of toxic chemicals and organisms in sewage, in sludge, and in the air at specific sites in sewage plants has raised suspicion regarding their possible effects on the health of workers. Wastewater treatment plant workers may be exposed to chemicals or organisms by direct contact with wastewater and sludge, or by inhalation of gases, particles, aerosols, vapors, or droplets. These hazards may enter the plant in soluble form or

attached to suspended solids.The employees working in the waste water treatment are greatly exposed to health and safety related hazards. In order to reduce the high accident rate, it is essential to ensure that considerations of health and safety are included that is with the provision of appropriate guidance or tools and to select the most appropriate systems to ensure environmental targets are met with the least possible health and safety risk. This can be achieved by undertaking an assessment of the occupational health and safety risks of systems for collection, transfer, treatment and processing of waste water.

Health and Safety Risk Assessment

The Health and Safety risk can be conducted by assessing the waste management requirements, assisting in the design and optimization of a waste water treatment plant, conducting environmental, health and safety risk assessments, managing the treatment of the plant and monitoring compliance of the treatment program.

In order to achieve safe wastewater treatment with minimal impacts on the environment and public health, appropriate assessments are required. This study highlights an integrated risk based approach for assessing inherent hazards associated with wastewater treatment plants in order to manage and mitigate the environmental and public health risks inherent with wastewater treatment.

Objectives of study

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The aim of this study is to identify these hazards at sewage treatments plants particularly in Malaysia. Then, based on likelihood and severity the most risky hazards in the area of study will be assessed. Next, according to produced list of hazard, proper management system via hierarchy of control (Elimination, Substitution, Isolation, Engineering Controls, Administrative Controls, Personal Protective Equipment) will be applied.The objectives of this study are to identify the types of hazards that may be encountered in a wastewater treatment plant, to recognize unsafe conditions and take appropriate measures whenever they develop. The goal is to prevent and minimize consequences of catastrophic releases of highly hazardous chemicals.

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