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WUPA SEWAGE WATER TREATMENT PLANT

The environment is the entire physical, chemical and biological factors external to the human host; and all related behaviors, but excluding those natural environments that cannot reasonably be modified. It also refers to the surroundings or conditions in which a person, animals or plants lives or operated.

The growing population and the process of utilization by man, the environment is subjected or exposed to protection and degradation processes, survival of any living organism, human inclusive in any environment is contingent upon the inability and quality of such environment.

Sewage treatment is the process of removing contaminants from wastewater and house hold sewage, both effluents and domestics. Its objective is to produce an environmentally safe fluid waste stream (or treated effluent) and a solid waste (or treated sludge) suitable for disposal or re-use (usually as farm fertilizer). Sewage is treated in order to produce a disposable effluent without causing harm to the surrounding environment and prevent pollution. It includes physical, chemical and biological processes to remove physical, chemical and biological contaminants. Here at WUPA, we don’t use chemicals in treating sewage because of the negative effect these chemicals might have on aquatic lives when water (treated effluent) is discharged into the natural flow.

Using advanced technology, it is now possible to re-use sewage effluent for drinking water although it is not implemented here because of the lack of the presence of water board Close to the treatment plant and also to reduce the risk of epidemics.

2.3              SEWAGE TREATMENT PROCESS

The sewage is gotten from municipal areas i.e. phase I, II and III central area of Abuja city and its immediate environment, although the entire F.C.T has not been covered or linked to this sewage treatment plant. Domestic sewage is what is basically treated here; industries are expected to have a mini sewage treatment plant of their own. Sewage treatment involves three (3) basic stages: Primary, Secondary and Tertiary stage and the entire treatment process here can be divided into Mechanical and Biological process.

Below is the flow chart of the sewage treatment process.

2.3.0           THE INLET

Sewage from households comes into the treatment plant through a sewer line and it moves with its natural force of gravity. Influent is the raw wastewater (i.e Sewage) that has been collected and conveyed to the plant for treatment. It includes all the waste and debris that entered the collection system or point.

FIGURE 1A Inlet                                      FIGURE 1B Inlet with an overflow

2.3.1           COARSE SCREEN

The sewage flow through a channel to the coarse screen from the inlet, at this point debris and wastes larger than 5cm are removed by mechanical means, the screened debris are then conveyed using conveying belt to the waste bin and later disposed

                                                                     

FIGURE 2A        Coarse screen              FIGURE 2B Rake that remove debris

2.3.2           LOW-LIFT PUMPING STATION OR SCREW PUMP

The sewage flow through a channel to the low-lift pumping station from the coarse screen and the sewage is been agitated by the screw pump and convey through a channel to the fine screen.

FIGURE 3A Low-lift pump                      FIGURE 3B Low-lift pump

2.3.3  FINE SCREEN

The fine screen consist of what is called lamellas and is arranged step by step for the removal of debris and wastes of above 4mm and are conveyed using the conveying belt to the screen press or compactor and deposited on the waste bins provided.

FIGURE 4 Fine screen

2.3.4           GRIT CHAMBER

Sewage from the fine screen flows directly into the grit chamber. The Grit chamber contains Scraper Bridge, grit Classifier and air blowers which are at the base of the chamber. The air blower helps to recover the fat and scum as froth because they are not biodegradable and also oxygenate the waste water. The grease and scum are removed by the scraper bridge and the sand sediments which are sent to the Grit pumping station then to the grit classifier.

FIGURE 5A Grit chamber                            FIGURE 5B Grit pumping station

2.3.5           DISTRIBUTION WELL

Here at the distribution well, the sewage is equally or evenly distributed to the aerator basins/tank or bioreactors.

FIGURE 6 Distribution well 

2.3.6           AERATION BASINS OR BIO-REACTOR

There are six (6) aeration basins in the plant and each have twelve (12) mammoth rotors, eight (8) mixers and each basin has a volume capacity of 27,700 cubic meter (m3). The basin is the heart of the plant. The mammoth rotors aid in oxygenation i.e initiate oxygen to the aeration basins for the survival of the microorganisms for complete biodegradation. The mixers also ensure a homogenous mixture for microorganisms to be in continuous contact with their food, ensure the direction of flow and prevent sedimentation of the sludge. biological process takes place at the basin i.e biodegradation and nitrogen cycle. Also, nitrification and de-nitrification occurs at the basin. Nitrification is the conversion of ammonium compounds into nitrite by nitrifying bacteria. While De-nitrification is the conversion of nitrate to nitrogen gas by bacteria.

Biodegradation is achieved by water-born micro-organisms such as bacterial, protozoa which convert organic matter to carbondioxide, water and energy. Sludge is formed at the basin and the detention period of the wastewater is 30 hours 4 minutes before it flow to the final clarifiers.

FIGIURE 7A Basin                                             FIGURE 7B        Basin                  

2.3.7           CLARIFIER

This is conical in shape, sedimentation takes place in the final clarifier. The clarifier has a scraper brush which is mobile that scrapes out the slugde particles at the side of clarifier basin for futher sedimentation. Sludge and water are separated here. Both the sludge and the bacteria settle down at the bottom of the clarifier and clear water overflow to the effluent of the UV station for final purification, while the sludge and live bacteria are pumped to the sludge pumping station.

FIGURE 8

2.3.8           ULTRA VIOLET RADIATION CHAMBER

The clear water flow to the UV chamber where live bacteria and other micro-organisms that had escaped the final clarifier are disinfected or killed by the UV radiation. The UV chamber is well protected such that human has no direct access to the radiation due to its harmful effect.

   

FIGURE 9

2.3.9           EFFLUENT

This is the treated water (clear water) that flows out of the treatment plant or discharged into the WUPA RIVER.

FIGURE 10A Effluent                                                 FIGURE 10B Effluent

2.3.10        SLUDGE PUMPING STATION

The sludge and live bacteria are sent to the station through the process of osmosis. At these point two things occurs here:

I.      RAS (Return Activated Sludge): The live bacteria are pumped back to aeration tanks to sustain the biological process

II. WAS (Waste Activated Sludge): When the sludge is in excess then it is pumped to the gravity thickener.

FIGURE 11A                                                      FIGURE 11B

A generalized, schematic diagram of an activated sludge process

2.3.11        GRAVITY THICKENER

The Gravity Thickener are basins which consist of a rotating rack that stirs the sludge until the sludge settles and become thickened at the bottom by centrifugal forces, and the extracted water is conveyed to the supernatant pumping station while the sludge is stored to a particular level before it is conveyed to the Dewatering system.

FIGURE 12

2.3.12           DEWATERING UNIT

This is where sludge is treated by addition of a measured amount of polymer which further extracts water from the sludge. The water extracted is pumped to the centrate pumping station while sludge is moved to the sludge lagoons where is completely dried by sun and ready to be collected and used as natural fertilizer. The excess water in the centrate and supernatant pumping stations from the Dewatering system and Gravity thickeners respectively are conveyed to the Distribution well where the water is cycled back as part of the influent.

2.3.13         SLUDGE LAGOON

It is a site for drying and storing of sludge.

2.3.14         MIMIC PANEL

This is a place where the entire process taking place in the plant and is controlled by a highly sophisticated PLC system. Personnel are stationed at the plant every day to monitor its activities and take hourly reading from it