LIQUID WASTE MANAGEMENT

This refers to the procedures and practices to prevent discharge of pollutants to the storm drain system or to watercourses as a result of the creation, collection and disposal of hazardous and non-hazardous liquid materials.

The sources of liquid waste in the city are industries, the airport and residential areas. There is one treatment plant serving the city; KIWASCO in Kisat.

Waste water types produced at the town include sullage and gray water.

The following are the definitions of commonly used terms in LWM

Soil water: waste water containing fecal matter

Grey water: waste water from kitchen, sinks, bathroom, laundry room that do not contain fecal matter.

Sewage: liquid waste containing suspended, colloidal and dissolves solids.

Sewer: a pipe conduit which carries sewage

Sewerage: network of sewers or pipes that are used for the purpose of transporting sewage.

Waste treatment: chain of treatment operations which reduce the volume and strength after which it renders the waste harmless and suitable for disposal.

Raw waste: untreated waste which is in a fresh state.

Sullage: same as grey water it refers to wastes flowing from the kitchen and bathroom

The soil water from the aforementioned facilities consists of potentially dangerous organisms that can cause the occurrence of water borne diseases like cholera, dysentery and typhoid. The organic content of these wastes is putriscible in nature and undergoes decomposition leading to emanation of obnoxious gases. 

Grey water is released from kitchens, bathrooms, laundry rooms and from wash hand basins while soil water is released from the water closets and urinals it contains fecal matter and urine. Sewerage system being used is the combined system whereby sanitary sewage and storm water are carried in a single sewer. Sewer Appurtenances include manholes, inspection chambers, grease traps, water closets, flushing tanks, urinals.

2.11.1 System Plumbing

Three types of plumbing system for drainage of facilities exist: two pipe system, one pipe system and single stack system. For one pipe system, there is one main pipe that collects both sullage and grey water from sinks, bathrooms and water closets then convey them to the building drain which joins the city drain but for two pipe system, there are two main pipes one for sullage the other for soil.

Reasons for waste water treatment:

To prevent ground water contamination

To prevent soil pollution

To protect aquatic life

To ensure re-use the treated effluent

To solve social problems caused by accumulation of waste water.

2.11.2 Treatment process 

2.11.2.1 Preliminary treatment

It involves the removal of waste water constituents that may cause maintenance or operational problems with the treatment operations, processes and systems. They include:

Screening

Comminuting- for removal of debris or rags

Grit removal- elimination of coarse suspended matter

Skimming- for removal of large quantities of oil and grease

2.11.2.2 Primary treatment

Done in the primary sedimentation tanks which are four in number. At this stage, a portion of suspended solids and organic matter is removed. This is done through physical operations such as:

Floatation

Sedimentation

Sludge is removed using a clarifier.

     Biological filtration

Nitrates, phosphates and ammonia are broken down by aerobic microorganisms at the top and anaerobic microorganisms at the bottom.

2.11.2.3 Secondary treatment

Here, sludge is further removed in the secondary sedimentation tanks which are also four in number. The retention period is 3hrs per tank.

 The final effluent is released into River Kisat which flows into L. Victoria.