Evaluation of Waste Water Treatment Plant Efficiency for Effective Disposal (A Case Study of Agbara Industrial Estate)
Chapter One
Overall objective
The general objective was to determine the effectiveness of the waste water treatment plant located at Agbara Industrial Estate for the production of acceptable water quality for discharge into in Agbara Industrial Estate.
Specific Objectives
- To evaluate the performance of the waste water treatment plant in reducing pollutants discharged into in Agbara Industrial Estate
- To determine the contribution of WWTP to pollution of in Agbara Industrial Estate.
CHAPTER TWO
LITERATURE REVIEW
This Section provides a detailed description of the waste water treatment processes, literature on the parameters to be assessed when assessing or monitoring water quality, the important parameters, and relevant concepts and theories that enable understanding the waste water processes as well as the national and international standards of water quality discharged as effluent in the public environment including public waters.
Waste water treatment process and waste water treatment plant/works
There are the preliminary stages of waste water treatment which are mainly aimed at removing the large particles that may interfere with the flow of waste water (Qasim, 1994). There are four main stages/ processes involved called Primary, Secondary, and Tertiary as well as an optional advanced stage (Qasim, 1994).
During the primary stage, physical process such as mechanical screening and grit removal is done, and this is then followed by sedimentation, which is aimed at simultaneous elimination of oil & fatty acids, as well as settle able and suspended solids that float. During this process, a small amount of biochemical oxygen demand (BOD) and nutrients (N and P) may be removed. Bar or bow screen, primary sedimentation, pH neutralization and Imhoff tanks are the required facilities necessary for this stage (Qasim, 1994; Miruka et al., 2018).
In the secondary treatment, biodegradable organic matter including organic nitrogen is converted into to carbon (IV) Oxide, water and nitrate through aerobic and anaerobic microbial processes. Stabilization ponds, activated sludge, aquaculture, rotating bio-discs, trickling filters and constructed wetlands are typical examples of secondary treatment processes (Qasim, 1994).
At the third stage of treatment which is also known as the tertiary treatment process, nutrients including total nitrogen consisting of organic nitrogen, ammonia nitrogen and total phosphorus including particulate and soluble phosphorus are removed. Further, removal of settleable solids and BOD is done. This is mainly meant to prevent eutrophication in sensitive surface waters. The facilities could include: constructed wetlands, aquaculture, chemical precipitation, denitrification and nitrification, disinfection among others (Jern, 2006; Qasim, 1994).
At advanced treatment stage, waste water treatment for further use in agriculture, industrial and municipal purposes is carried out. Techniques used here include reverse osmosis, electro dialysis, selective ion exchange, hyper-filtration, chemical treatment and detoxification.
Agbara Industrial Estate (Agbara Industrial Estate): Wastewater treatment process
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The treatment process in Agbara Industrial Estate water treatment plant involves the following processes:
CHAPTER THREE
MATERIALS AND METHODS
This chapter describes the site of study and its environment. It also details the methods used to conduct the study (sampling designs, laboratory analysis protocols) and data analysis.
Population, Climate and Hydrology around the wastewater treatment plant (WWTP)
The treatment plant is located in Mavoko Sub-county (also known as Athi River) which has an area of 827.2 Km2 with the population of 322,499 people and population density of 390 persons per Km2 (KNBS, 2019). The area falls within Kapiti Plateau. Its estimated altitude is 1400m asl. The area’s rocks are predominantly volcanic that are derived from the Cenozoic era (Agbara Industrial Estate, 2016). Pellic Vertisols are also dominant in the area (black cotton soils) (Agbara Industrial Estate, 2016). The area falls within the in Agbara Industrial Estate basin that drains the area as it snakes towards the Indian Ocean (WRA, 2019). The WWTP is situated adjacent to the in Agbara Industrial Estate.
CHAPTER FOUR
RESULTS
This section presents the findings of the study. Interpretation of data was by comparing the national and global waste water quality standards before being discharged into the environment.
CHAPTER FIVE
CONCLUSIONS AND RECOMMENDATIONS
CONCLUSIONS
The study findings show that, the effectiveness or performance of the treatment plant was generally low due to low reduction potential of the treatment plant which subsequently led to effluent values that do not meet the acceptable maximum levels of pollution in the water for discharge into the public waters and the environments.
The performance of waste water treatment plant was not effective in reducing pollution load in terms of chemical pollutants specifically nitrates, phosphates and heavy metals i.e. mercury, lead copper, cadmium and selenium. Biological parameters (Total coliforms and the E. coli) remained unchanged after treatment process of the influent. The ineffectiveness or inefficiency was more pronounced in rain season. However, the treatment plant was effective in reducing pollution load for chemical oxygen demand (COD), biological oxygen demand (BOD). Generally, there was high concentration of mercury, lead, selenium and copper in the influent from the Agbara Industrial Estate and very low to undetectable levels of arsenic and cadmium. For physical parameters, the waste water treatment plant performed poorly by ineffectively not reducing Total dissolved solids (TDS), Total suspended solids (TSS), colour and odour. However, pH, conductivity and temperature increased in the effluent but were within allowable values described by Nigerian and Global standards.
Seasonal weather changes significantly affected the concentration of pollutants in waste water treatment plant. Phosphates, mercury, COD, BOD and coliform bacteria were high during dry season while nitrates, lead and selenium increased during rains. Copper remained relatively unchanged for both seasons although the concentration was high beyond acceptable limits by Nigerian and Global standards.
Conductivity, pH, salinity and temperature increased in the effluents but reduced during the wet season when compared to dry season. However, despite the increase, the concentrations were within the acceptable ranges recommended by Nigerian and Global standards. The influents in dry season were colorless and odorless but became darkish brown with pungent smell during rains. Total dissolved solids (TDS) and Total suspended solids (TSS) increased highly during wet season (rains) and their concentrations were above acceptable Nigerian and Global standards.
Generally, there was higher contamination at discharge point of the effluent from treatment plant during dry season with low levels upstream. Contamination reduced downstream as the stream continued to flow. There were high concentrations of heavy metals on the river (both upstream and downstream) attributed to anthropogenic activities upstream coupled with the ineffectiveness of the treatment plant contributing less to reduce the load downstream.
For physical parameters, conductivity, pH, salinity and even temperature were higher downstream than upstream, although all parameters were lower than at the overflow pools for both dry and wet seasons. Both upstream and downstream had clear waters compared to the overflow waste waters which were reddish brown with bad odor. The trend was the same total dissolved solids and total suspended solids especially during rains.
RECOMMENDATIONS
From the conclusions, the following recommendations were suggested from the study;
The Agbara Industrial Estate waste water treatment plant needs to be upgraded, redesigned or replaced with a new one in order to achieve more effectiveness in water treatment from the Mavoko area taking into consideration the grown population rely on the same.
The redesigning should include pretreatment phase before the effluents reach the treatment or segregation of wastes to increase the efficiency. Other areas which require attention are the anaerobic ponds to increase biodegradation and may be use of antiseptic chemicals to reduce coliform bacteria.
In addition, monitoring of water quality in waste water treatment or in Agbara Industrial Estate should consider the seasonal weather variations which influenced pollution load.
Finally, further research should be done to find the key sources of pollution on in Agbara Industrial Estate besides the less effective waste water treatment plant at the Agbara Industrial Estate. This should be coupled with studying the role of river gradient in cleansing the pollutants.
REFERENCES
- Alloway, B. J. (1995a). Heavy metals in soils. (2nd Edition). Blackie, New York.
- Al-Mutaz I & Al Ghunaimi M. (2001). Performance of Reverse Osmosis Units at High Temperatures. The Ida world congress on desalination and water reuse, Bahrain, October 26 – 31, 2001.
- American Public Health Association, APHA (2012). American water Association. AWW, Water pollution control Federation. Standard Methods for the examination of water and waste water 22nd edn. Washinton DC
- American Public Health Association, APHA. (1998). Standard methods for the examination of water and wastewater. 20th edition. American Public Health Association, Washington, DC.
- Bergeson, L. (2008). “The proposed lead NAAQS: Is consideration of cost in the clean air act’s future?”. Environmental Quality Management 18: 79-88.
- Bhatia S. (2002): Handbook of Industrial Pollution & Control: Air, Water, Wastes, & Pollution Control in Chemical Process and Allied Industries. Vol. II. CBS Publishers and Distributors, New Delhi: 20-500.
- Chen, CW, Chen CF, Dong, CD (2012). Distribution and Accumulation of Mercury in Sediments of Kaohsiung River Mouth, Taiwan. APCBEE Procedia. 2012; 1:153– 158.
