ABSTRACT
The physicochemical and bacteriological qualities of
effluents from WUPA Sewage Treatment Plant, Abuja were determined within the
duration of twelve weeks. Grab method of wastewater sampling was used while
sampling for the analysis. The sampling and analysis were carried out between
May and September, 2015. Samples were collected at the inlet to the treatment
plant (SCP 1), outlet of aeration tank (SCP 7C-2), outlet of sedimentation tank
(SCP 8C-3), effluent outlet of the treatment plant (SCP 4), 10m upstream and
10m downstream of the receiving water body (River WUPA).
Parameters analyzed included; biochemical oxygen demand (BOD5),
chemical oxygen demand (COD), total suspended solids (TSS), nitrate as nitrogen
(NO3-N), nitrite as nitrogen (NO2-N), ammonium as
nitrogen (NH 4-N), dissolved oxygen (DO), chloride (CL-),
sulfate (SO4-), faecal coliform (FC), total coliform
count (TCC), pH and electrical conductivity (EC). The results of the sample
analysis showed that the average removal efficiencies of the treatment plant in
terms of BOD5 and COD were 92% and 83%% respectively, while the
average removal efficiency for TSS was 89%. The dissolved oxygen (DO), nitrate
(NO3-N) and nitrite (NO2-N) concentration of the effluent
were observed to have increased by an average of 46%, 61% and 72% respectively
relative to the inlet values.
The average removal efficiencies for ammonium as N (NH4-N),
CL- and SO4- were 58%, 19% and 30% respectively
and the bacteriological contamination of the wastewater was averagely removed
by 93% and 92% for faecal coliform (FC) and total coliform count (TCC)
respectively. The pH and electrical conductivity (EC) were varied by 3% and 11%
respectively.
The study revealed that there was no adverse impact of the
effluent water on the receiving water body (river WUPA) in terms of
physiochemical parameters as the treated effluent from the facility conformed
to the specified discharge limits for WHO (2007) and NESREA (2011), but in
terms of the bacteriological parameters; values of the total coliform count
(TCC) and faecal coliform (FC) were observed to be higher than that of the
river at both upstream and downstream sections, which necessitates the
development of a maintenance plan for the treatment plant with emphasis on
proper maintenance of the unit processes of the treatment plant and UV treating
the effluent properly before discharge into the receiving water body.
A simple mathematical model was developed for BOD5
and TSS using mathematical analysis and the relationship obtained are as shown
below:
Y = 0.4218x2 – 19.6070x + 126.08; where Y = BOD5
(mg/l), x = Hydraulic retention time (Hr.) and Y = 0.6471x2 –
23.3510x + 146.91; where Y = TSS (mg/l), x = Hydraulic retention time (Hr.).
CHAPTER ONE
INTRODUCTION
1.1 Background
The major sources of water for
human uses include but are not limited to lakes, rivers, soil moisture and relatively
shallow groundwater. Three main factors that are affecting water demand over
the past century are Industrial growth, Population growth and Irrigated
Agriculture. Over the years water pollution has been of serious concern. The
major pollutants are pathogens, nutrients, organic matter, heavy metals, toxic
chemicals, silt and salt and suspended solids (Moazzam et al., 2015).
Particularly, South Asia and Southeast Asia are facing severe problems of water
pollution. Renowned Rivers (Yellow in China, Ganges in India, and Amu and Syr
Darya in Central Asia) are top on the list of the world‟s most polluted rivers
(Sushil, 2008). The case is similar in the developing nations of the world as
most rivers in the urban areas are heavily polluted with domestic sewage,
industrial effluents, chemical and solid wastes (UNEP, 2002).
Industries have become integral
part of modern society; as a result production of wastes is inevitable in
industrial activities (Dipu, et al., 2015). A material becomes waste when it is
discarded without expecting to be compensated for its inherent value. Those
wastes may pose potential hazard to human and the environment when improperly
treated, stored, transported or disposed off or mismanaged (Misra and Pandey,
2004). Surface water bodies in developing countries are under constant threat
as a result of indiscriminate discharge of polluted effluents from industrial,
domestic and agricultural/sewage activities. (Kambole, 2003). Nigeria not an
exception, water pollution is the most serious environmental problem due to
disposal of solid and liquid wastes on land and surface water. Abundant as it
may
seem, water in its clean state is
one of the rarest element in the world (Omole, and Longe, 2008). Like all
scarce resources which have regulations guiding their exploitation, ownership,
preservation and sustenance, water is protected by a body of laws, policies and
regulations in order to prevent abuse FGN (2000). It is the use to which the
water is to be put that determines the quality standard that must be imposed,
Anyata and Nwaiwu (2002). For instance, water meant for consumption, food and
pharmaceutical industrial purposes would have higher standards than water for
agricultural production.
The level at which the sewage has
to be treated depends on where it will be disposed and treatment standards are
higher for disposal into freshwater bodies than that into the sea. However,
typically even where sewage treatment plants (STPs) exist, sewage collection
networks are inadequate; some portion goes for treatment and the rest flows
into drains. Sometimes wastewater stagnates in pools from which it leaches into
the groundwater table and contaminates underground aquifers.
The WUPA Sewage Treatment Plant
(WSTP) Abuja is an environmentally friendly project which has been designed to
ensure that the ambience in the city remains clean and pleasant. It also
ensures that the quality of the underground water is improved upon and the
streams remain clean as only treated water is discharged back into its natural
flow. The concept of the aeration basin sewage treatment plant has been lauded
the world-over for its immense health and environmental benefits. It
tremendously reduces the risk of epidemics associated with human waste disposal
which might be traceable to the release of untreated water back to the stream
and rivers.
Monitoring of the environmental
parameters of the effluent would allow having at anytime, a precise idea on
performance of the wastewater treatment plant and if necessary, appropriate
measures may be undertaken to prevent adverse impact on the environment. The
obtained result will be very much useful in identification and rectification of
operational and maintenance problems. The primary cause for degradation of our
water resources is the pollution caused by sewage discharged from cities and
towns. Hence, the treatment plant should be routinely checked for their
performance and flaws in the treatment units. This is usually carried out based
on the removal efficiency of various wastewater characteristics. The WSTP adopt
the biological treatment using activated sludge process. The BOD removal and
degree of bacteria removal for a properly operating aerobic activated sludge
treatment plant are estimated to be 80-95 and 90-95 percent respectively
(Punmia et al., 2005).
The completion of the WUPA Sewage
Treatment Plant heralded the arrival of a new dawn for the inhabitants of
Abuja, capital and seat of government of the Federal Republic of Nigeria, the
most populous nation in Africa. Construction works on the WUPA sewage treatment
plant (WSTP) Abuja started in 2001, blazing the trail for being the largest of
its kind in sub-Saharan Africa. Its state of the art, high technology and
computerized accessories rank this treatment plant at par with the most modern
treatment plants in the world (WSTP Abuja, 2007).
Sludge which is produced as a
solid-by product of the sewage treatment process is of agricultural benefit as
it could be collected and used as natural fertilizers to boost the growth and
production of cash and food crops by the local farmers. The inhabitants of
Abuja and the
surrounding communities will
continue to be thankful to the government for establishing this sewage
processing plant within its domain. It epitomizes the position of government to
provide a strong and virile economy by ensuring and safeguarding the
environment and health of its citizens, designed to meet the requirements of
700,000 PE (Population Equivalent). The plant can accommodate an Average Dry
Weather Inflow of 5,500 cubic meters per hour or 131,250 cubic meters per day.
The entire treatment process can be divided into mechanical and biological
phases. At no stage of the process is the addition of chemicals required. After
the sewage has passed through the first stage of mechanical treatment, it
enters the Aeration tanks, followed by the final clarifier where the sludge and
water will be separated through a biological process. Figure 1.1 is the process
layout of the WUPA treatment plant (WSTP Abuja, 2007).
The environmental impact of the
WSTP and its benefits to the inhabitants of Abuja and its environs symbolizes a
new approach to waste management and healthier living by the Nigerian
Authorities. The completion of this project is a further testimony to the
engineering capabilities of SCC Nigeria Limited and its total commitment to the
overall development of Nigeria.
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