Essay --

There are several pollutants present in municipal wastewater, including oxygen- demanding substances, pathogen, inorganic and synthetic organic chemicals, and nutrient. Dissolved oxygen in water is necessary to support aquatic life, consumed by aerobic bacteria and other aquatic organisms for living purpose. Biochemical Oxygen Demand (BOD) is the amount of oxygen that would be consumed if all the organics in water were oxidized by bacteria and protozoa (Interlab Supply, 2010). Microorganisms will break down the organic matter by consuming the dissolved oxygen present in the wastewater and BOD is normally used to measure the performance of sewage treatment plant. (United States Environmental Protection Agency, 2004) The wastewater effluent produced by the treatment plant has a high content of organic pollutants such as ammonia which will demand more oxygen. These substances destroyed and converted to other compounds by bacteria when the water has sufficient oxygen. Large amount of bacterium that widely spread in wastewater is also known as pathogens and hazardous to our health while waste products in wastewater are most often liquid or solids and they can be biological, chemical or radioactive dangerous. Apart from having adverse health involvements, wastewater contamination can also have natural and ecological affects, including the degradation of ecosystems which include decreasing of aquatic plants that help to preserve the condition of waterways or biodiversity loss. For example, loss of aquatic life likes fish and crustaceans that are an important part of both animal and human diet. Disinfection of wastewater and chlorination of drinking water supplies manage to reduce the occurrence of waterborne diseases such as typhoid fev... ...sociated with screenings. However, comminutors and grinders can also create problems for downstream processes, such as increasing plastics build up in digestion tanks or rag accumulation on air diffusers. In addition, solids from comminutors and grinders will not decompose during the digestion process. If these synthetic solids are not removed, they may cause biosolids to be rejected for reuse as a soil amendment. Large amounts of grit and sand entering a treatment plant can cause a serious operating problem that is needed for treatment. Grit includes sand, gravel, cinder, or other heavy solid materials that are â€Å"heavier† than the organic biodegradable solids in the wastewater. Removal of grit prevents unnecessary abrasion and wear of mechanical equipment, grit deposition in pipelines and channels, and accumulation of grit in anaerobic digesters and aeration basins.