Research Paper Help on Sewage Treatment Plants

SEWAGE TREATMENT PLANTS

  1. What improvements will be made to sewage treatment plants over the next 20 years?

The key goals for changes in sewage treatment in the next 20 years will be mainly to improve microbiological safety, control corrosively as well as minimize concentrations of disinfection by-products. However, these objectives are somehow conflicting. For instance, disinfection is improved at low PH, and in the presence of higher concentrations of disinfectants. On the contrary, low PH usually intensifies corrosively, and maximum concentrations of disinfectant results in creation of more disinfection by-products. New treatment methods will be necessary to improve filtration such that it will help to eliminate the microorganisms that are very complex to inactivate. Thus, this will permit disinfection by the use of lower concentrations of disinfectants. Disinfection by-products will be managed through the elimination of solid material by improving coagulation or the addition of adsorption, oxidation or membranes, as part of the processes above convectional treatment. This will enable the utilization of lower concentrations of disinfectants for the purpose of providing adequate disinfection and the utilization of high PH to meet the requirements of the lead and copper rule (U.S 1995, p. 11).

There are two common disinfectants that do not use chlorine or products that contain chlorine, including ozone and ultraviolent radiation. These two products will be used more frequently. This is because they do not produce disinfectant residual for distribution system protection. However, a little amount of chlorine or products containing chlorine will be required for the purpose of maintaining the protection of the public. Another approach to biofilm control in the sewage distribution system entails the elimination of biodegradable organic matter in the treatment plant. This will minimize the demand for biocide in the delivery system, thus economizing on the utilization of chlorine and its elements of chlorine (U.S 1995, p. 11). In summary, with the advancement in technology, the major improvements that will be made to sewage treatment plants over the next 20 years will include;

  • Membrane treatment as an alternative for both the convectional filtration as well as primary disinfection utilizing oxidants.
  • Membrane treatment as a more useful way of the removal of natural and synthetic organics from the sewage water.
  • The removal of metallic substances in the delivery system and consumer plumbing.
  • The establishment of methods for alleviating water in the delivery systems that do not rely on the preservation of a residual oxidation in the delivery system.
  • The establishment of additional strategies for the purpose of protecting membrane disinfected water from contamination during distribution.
  • The establishment of methods for real time assessment of the microbiological contaminants as well as particulates, which includes a number of vital pathogens (Visvanathan 2002).
  • The establishment of more sophisticated methods for the purpose of maintaining high water quality during storage in some of the huge distribution system reservoirs.
  • Describe the entire process for bioinformatics analysis.

Sewage treatment plant normally involves several stages depending on the particular substance that is contained in the water. The stages include mechanical elimination of coarse matter and sand, neutralization, pre-clarification for the purpose of separating the undissolved substances as well as substances that are precipitated during neutralization, equalization of the sewage water quality, biological treatment,  and finally secondary clarification for the purpose of separating the biological sludge from the treated water (Copper et al 1991, p. 28).

Mechanical Cleaning

Mechanical cleaning helps in the removal of most of the huge solids, including rags and sticks that are normally contained in the sewage water. These are normally eliminated by screens that consist of metal bars, which are spaced at 19 mm intervals and are usually placed across the influent channels (Othmer 1973, p. 33).

Neutralization

The sewage water is usually strongly acidic as a result of how it is produced. For the purpose of protecting the bacteria within the treatment plant, lime milk is usually included to the sewage water depending on the PH level. This helps in precipitating inorganic matter as well as some of the organic matter.

Pre-clarification

At this phase, the precipitation materials of the neutralization procedure together with other materials descend to the surface, and are eliminated mechanically. The resulting sludge is then collected together with the sludge obtained from other treatment stages and then moved to the sewage sludge treatment system (Kemmer 1971).

Primary Treatment

The initial step of this phase includes Pre-aeration. The sewage water is aerated by air that is propelled through pierced pipes that are usually placed near the base of the tanks. This aeration is usually carried out to make the water less intense, enabling the grit to separate. The air also allows dissolved oxygen for the bacteria action to take place. The subsequent step of the primary treatment is sedimentation. The water is then passed through the sedimentation tanks, where the suspended solids are allowed to fall to the surface and scum is allowed to rise to the surface, while the clarified effluent passes on. The solids are then eliminated from the surface of the tank using scrapers, and scum is swept off using water jets. The scum as well as solids are then collected at the same point where they are mixed to form sludge (Henze 2002).

Secondary Treatment

At this stage, sludge from the sedimentation tanks is absorbed anaerobically in huge reservoirs, and then additional absorption takes place in the lagoons before draining in dewatering beds. Within the sludge absorbers, the temperature is maintained at 370C. At this point, the organic compounds contained in the sludge are transformed into carboxylic acids and then to methane and carbon dioxide.  After living the absorbers, the sludge undergoes a 50% Volume decrement (Olsson 1999). It is then taken back to the ponds and lastly to dewatering beds. At this point, all the pathogens are killed by sunlight. At this stage, the sewage water is sent direct to open air oxidation ponds to minimize their Biochemical Oxygen Demand (BOD) before undergoing pond oxidation (Tong et al. 1980). The fixed growth reactors (FGR’s) consist of tall, spherical tanks that are covered with fiberglass, which are each filled with about 36 million 10cm diameter wheels. Microorganisms are usually on these wheels, and this helps minimize the BOD of the sewage by about 70%. The sewage water is sprayed on the wheels and percolates down with the organics being decreased to carbon dioxide, methane, and a small quantity of foul-smelling Hydrogen sulfide. From the surface of the FGR, the effluent is channeled to a secondary sedimentation tank where sludge is eliminated, which is the channeled to join the incoming sewage water and complete the process again (Henze 2002).

Reference

Cooper, P. F., Freeman, D. J., & Lidgitt, P. J., 1991. U.S. Patent No. 5,006,232. Washington, DC: U.S. Patent and Trademark Office.

Henze, M. (Ed.)., 2002. Wastewater treatment: biological and chemical processes. Springer.

Kemmer, F. N., Robertson, R. S., & Mattix, R. D., 1971. U.S. Patent No. 3,619,420. Washington, DC: U.S. Patent and Trademark Office.

Olsson, G., & Newell, B., 1999. Wastewater treatment systems. Modelling, Diagnosis.

Othmer, D. F., 1973. U.S. Patent No. 3,772,187. Washington, DC: U.S. Patent and Trademark Office.

Tong, R. M., Beck, M. B., & Latten, A., 1980. Fuzzy control of the activated sludge wastewater treatment process. Automatica16(6), 695-701.

UNITED STATES. , 1995. Safe drinking water: future trends and challenges: an Environmental Futures report. Washington, DC, The Board.

Visvanathan, C., & Aim, R. B., 2002. Membrane Bioreactor Applications in Wastewater Treatment.