Elements Surrounding Wastewater Treatment Plants - Report Example

Student Name Student ID Course Name Course Convenor Semester 1 Due Date Table of Contents I. Introduction.................................................................................................................. 3 II. Characteristics of wastewater treatment...................................................................... 4 III. Objectives of wastewater treatment............................................................................. 4 IV. Need for water treatment............................................................................................. 5 V. Wastewater collection systems.................................................................................... 6 VI. Wastewater treatment process..................................................................................... 7 VII. Biological and aerobic system..................................................................................... 9 VIII. Conclusion................................................................................................................... 10 Report on Elements Surrounding Wastewater Treatment Plants Introduction The world is embracing the environmental conservation program of treating wastewater. Town councils have taken up the initiative of treating wastewater that comes from homes as well as businesses within the town (Shariff, Riyaz, et al 62). Recently there has been an increase in reuse of treated wastewater. This has prompted countries such as Australia to have separate systems of treating wastewater and storm water in order to satisfy the demand. This report will look into the crucial needs of treating wastewater as well as the objectives, characteristics of the wastewater treatment plants. Wastewater from homes is divided into two categories; black water, which is discharged from toilets, and grey water, which comes from used water in the kitchen sinks, laundry, and bathrooms. Commercial premises such as hotels, shops, or restaurants are also allowed to discharge wastewater into the municipal water treatment system. In addition, some industries have been allowed to discharge their effluent into the municipal system. The municipal authorities have imposed restrictions on industries in terms of the amount of wastewater to be discharged into the system (Cheremisinoff 46). This restriction is seen as a protective measure to safeguard wastewater treatment workers and the infrastructure of the treatment plant. The authorities have also stipulated effluent standards and parameters. While setting the standards, environmental values, including public consumption of the treated water, are assessed (Metcalf and Eddy 24). However, the standards are controlled by the availability of technology and cost of practicality. These are most common parameters standards used globally. Parameter Limit Biochemical Oxygen Demand 5 15mg/L SS 15mg/L PH 6.6 to 8.5 Dissolved Oxygen > 2mg/L TN 5mg/L TP 1mg/L F. Coli forms 200 org/100mL Source: (Metcalf and Eddy 44) Characteristics of wastewater treatment Wastewater treatment plants observe levels of organic matter, solid content, dissolved oxygen, total organic carbon, nitrogen, phosphorus, biochemical oxygen demand, and chemical oxygen demand in the wastewater. The total organic matter in the wastewater will necessitate the bulk treatment required during the treatment process, which in turn will enable the plant to avoid depletion of oxygen in the treated water. Dissolved oxygen is quite influential in determining the quality of treated water coming from the plant. In many treatment plants, wastewater depletes the dissolved oxygen at a faster rate, thereby hindering the re-aeration process. The composition of solid material in wastewater is 0.1%. Out of this fraction 70% is organic while 30% is inorganic. Proteins carbohydrates and fats are classified as organic whereas inorganic is composed of grits, metal and salts (Cheremisinoff 236). The chemical oxygen demand and organic carbon are the main elements used in characterising the content of organic matter in wastewater. Objectives of wastewater treatment The main aim of wastewater treatment plants is to reduce the level of contaminants in the wastewater. The wastewater contaminants include; solids, harmful nutrients, pathogenic organisms that deplete oxygen in the water, oils, and grease, as well as industrial contaminants such as heavy metals. The focus has changed over the years; from removing solid contaminants, to the removal of oxygen depleting material and nutrients that may cause eutrophication (Metcalf and Eddy 141). Additionally, wastewater treatment aims to reduce environmental dangers to the environment associated with untreated water. Untreated water may cause extensive pollution and the degradation of the environment. Wastewater treatment has a sludge treatment and management obligation. This obligation ensures that the higher in volume of sludge originating from wastewater, is stabilised and beneficial for human use, for instance in agriculture. Need for water treatment This technology of wastewater treatment is extremely beneficial since it provides enough water for agricultural use and industrial processes. There is a substantial need for water reclamation and reuse since wastewater is a massive threat to the environment and marine life. The concerns raised on health issues caused by wastewater put the burden on industries, and forced them to treat their effluents before discharging the effluents back to the source (Cornwell, David, and Lee 57). Wastewater treatment and recycling, adds to the overall water needs of the public in large cities. The highly treated effluent is pumped back into the city's water grid to add to the scarce water source for the municipality. The graph below shows the volume of water reused between 1993 and 1997 in Australia. Source: (Ball, Sinclair, and Merz 9) Wastewater collection systems The municipal wastewater system consists of manholes, pump stations, and drainage system pipes which rely on the force of gravity. Local sewers are usually located at the rear property boundary, lower than the water main, to avoid contamination of the town water supply (Metcalf and Eddy 331). The collection systems are designed so that wastewater flows satisfactorily at an adequate speed. The systems also have self cleansing features. The flow of waste water in the pipe does not exceed ¾ of the pipe. This measure ensures that the wastewater does not flow out of the pipe at low pressure points. The sewers are designed to handle low volume during dry weather and higher volume during wet weather. The drainage pipes are channelled from commercial premises, institutions, and small scale industries. During wet weather, the drainage system allows for infiltration or increased inflow of rain. Source (“Wastewater collection systems.” 7) The manholes provide access to the passage during the cleaning process. They are placed at intervals to allow changes in pipe sizes and pipe junctions. The collection system is quite economical, with relatively few pump stations that pump the wastewater to the next stage of the water treatment process. The system has submersible pumps placed at designated points of the system. Source (“Wastewater collection systems.” 8) The diagram above depicts a typical wastewater collection system - indicating the pumps and sewer lines. The water flow varies from throughout the day. The peak flow times are early in the morning and early in the evening. However, the system faces challenges such as surcharging, deterioration of drainage pipes, and excessive inflow. These problems lead to discharges of raw wastewater into the surrounding environment. Such challenges have led to municipalities using traditional trenching methods for sewer installations. There are various methods of relining sewer lines. Liners are normally installed in existing sewers. Water inflation is a perfect example of relining technique (Veissman and Hammer 171). The problem is also fixed by design techniques to avoid the build-up of slime in the pipes. Large industries are embracing trenchless technology, which includes using tunnelling techniques. The discharge regulation and maintenance is strictly followed. In Australia, the government has implemented a policy known as ‘trade waste control’. This policy stipulates the specified standards of water treatment plants. Wastewater treatment process The municipality has employed the conventional method of treating water. This process has four crucial stages; preliminary, primary, secondary, and tertiary. Wastewater treatment is achieved through physical and biological methods (Tchobanoglous and Edward 466). Chemical processes are not that significant since the biological technology has advanced tremendously (Shariff, Riyaz, et al S62). In the preliminary stage physical methods are applied. This includes the screening and removal of grits and solid contaminants. The aeration method is used to remove grit and solid sediments. Sludge is then directed to the primary stage where sedimentation occurs. Sedimentation allows solids to settle at the bottom of the sedimentation tanks or centrifuge tanks (Tchobanoglous and Edward 467). The sedimentation process provides a mechanism to remove scum from the surface. The next stage is the secondary stage where biological treatment takes place. The oxygen depleting organisms are eliminated from the wastewater. This step reduces biochemical oxygen demand, as well as the suspended solid material. Nutrient removal and reduction of eutrophication also takes place at this stage. The final stage is the tertiary treatment stage. At this stage advanced treatment procedures, such as sand or carbon filtration and application of membrane technologies such as reverse osmosis and microfiltration, occur. Source: (“Conventional Wastewater Treatment Process” 2) Disinfection comes in at the advanced stage of treatment. It is a crucial step where undesirable environmental residue and harmful pathogens are removed using various methods. Such methods include; the use of UV light and chlorination (Tchobanoglous and Edward 469). Biological and aerobic system Biological treatment comes after the wastewater has gone through sedimentation. This procedure removes suspended residual organic material in the effluent. Biological treatment is categorized according to the level oxygen used up. The system has both aerobic and non-aerobic biological treatment systems. In the aerobic system, the aerobic microbial organisms transform the suspended organic matter into matter that may settle and then be removed physically (Tchobanoglous and Edward 409). Municipal wastewater treatment systems have incorporated trickling filters into their biological filtration system. The system produces high quality effluents and has a low maintenance cost (Metcalf and Eddy 391). In recent years, the wastewater treatment plants for municipalities have transformed and are using the activated sludge process. This process is more compact than trickling filtration process with variations in oxidation and aeration. Both of these processes are anaerobic procedures. Anaerobic microorganisms digest the sludge in the wastewater. The sludge is broken down into stable compounds such as carbon dioxide and methane. In addition, the activated sludge process eliminates the smell of the effluent. Comparison of nitrogen and phosphorus removal efficiency Treatment method Characteristic of nitrogen & phosphorus (mg/L) Removal efficiency (%) TKN TP TKN TP Aerobic Aerobic lagoon 109 31.4 84 64 Oxidation ditch system 52 24 92.3 58.3 Anaerobic Anaerobic digestion 76 - 181 5 - 32 28 17.3 - 23 Facultative Anaerobic - aerobic lagoon n/a n/a 26.4 16.2 SHR 50 - 380 18 - 162 94 - 98 97 AAO 49.0 10.4 69.1 28.5 Source: (Tchobanoglous and Edward 399) Conclusion Wastewater treatment plants are located in areas that allow the water to gravitate freely into the system. The area is usually found in a non-populated low-lying area. Analysis is usually carried out to ensure the plant minimises the potential pollution (Metcalf and Eddy 412). The treatment facility meets the main objective of treating and purifying water for the public (AWWA 17). The National Water Quality Management Body ensures water supplied by the municipality is safe for public consumption. Cleaning maintenance and odour control processes are carried out within the specified regulations set up by governing authorities and environmental agencies. The scarcity of water in the world has contributed to the increase in the reuse and conservation of water. In response to the rising demand for water, government and environmental agencies have initiated programs to ensure that there is a stable storm water treatment plant in urban centres (Ball, Sinclair, and Merz par. 14). This increases the water surplus in cities as long as the catchment and harvesting programs are well managed. Works Cited AWWA. Water quality and treatment: a handbook of community water supplies. 4th ed. Toronto, Ontario: McGraw-Hill. 1990. Print. Ball, Jonas, Sinclair Knight & Merz Pty 2001, Inland Waters Theme Report. Web. Accessed on 21 May 2012. Cheremisinoff, N. P. Handbook of Water and Wastewater Treatment Technologies, Butterworth-Heinemann, 2002. Print. “Conventional Wastewater Treatment Process” n.d. JPEG file. Accessed on 21 May 2012. Cornwell, David A. & Lee, R. “Waste stream recycling: its effects on water quality.” J. Am. Water Works Assoc. 86.11 (1994): 50-63. Metcalf and Eddy Wastewater Engineering, Boston: McGraw-Hill. 2003. Print. Shariff, Riyaz, et al. "Advanced Process Control Techniques for Water Treatment using Artificial Neural networks1." Journal of Environmental Engineering and Science 3 (2004): 61-67. Tchobanoglous, George and Edward Schroeder. Water Quality, Massachusetts, USA: Wesley Publications, 1985. Print. Veissman, W and Hammer M. J. Water Supply and Pollution Control, 6th ed, Massachusetts, USA: Wesley, 1998. Print. “Wastewater collection systems.” Wallbridge and Gilbert engineers, (2007): 1-30. PDF file. 21 May 2012. Read More