Eco-friendly Wetland Park by KPT - A viable solution for combating with land based source of marine pollution

Karachi Harbour is at the receiving end of large quantum of City's municipal cum industrial effluents through 6 major drains and several smaller outfalls. The major drains and their assessed volumes are as under:

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1. Lyari River                220 mgd

2. Nehr-e-Khayyam              16 mgd

3. Soldier Bazar Nallah        30 mgd

4. Railway Nallah               4 mgd

5. Pitcher Nallah               7 mgd

6. Karli Nallah                 7 mgd

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The effluents besides containing high concentration of toxic chemicals and heavy organic load also transport solid waste in the shape of floating debris and suspended plastic / polyethylene material. Presently, the most significant factors adversely impacting on the marine eco-system in the port area are the sewage and nutrient inputs. The effects of these input is to reduce the dissolved oxygen level that increases the BOD to critical levels. It is also apparent that due to the major impact of sewage and nutrients, the affects of other pollutants, such as trace metals and oil play a secondary role. According to the available data, some trace metal concentrations in the port can be considered at a level where chronic toxic effects would be expected.
These trace metals include copper, chromium, zinc and arsenic. In an improved oxygen environment, where species of aquatic biota were less restricted, these trace metal levels would become a cause of greater concern.
The adverse impact of these pollutants has jeopardised the marine eco-system not only in the harbour but also on the coast. The high toxicity present in the untreated industrial effluents and the oxygen starvation caused by the raw sewage has drastically strained the marine life and whatever fish survive in the area is unfit for human consumption.
The above adverse impact is not restricted to Karachi harbour only because part of these pollutants is exported to the coastal water with the tide twice a day. Also, this certainly affects the fish population in the coastal waters.
The current sewage condition in the city required a complete separation of sewage and storm water drainage systems, transmission of all sewage and wastewater through closed sewer system to treatment plants and treatment of raw sewage to a level, meeting the EPA regulations' before discharging into the sea.
The Karachi Water & Sewerage Board is main body to cater treatment of all liquid waste. Presently, three sewage treatment plants with a total designed capacity of 150 mgd are installed in the city and sewage generated in different parts of the city is carried to these plants for treatment.
To cater the increasing load of liquid waste, KW&SB comes up with a solution of Greater Karachi Sewerage Plan (S-III) which geared towards improving environmental and sanitation conditions of Karachi through a well-integrated system of collection, treatment and disposal of sewage.
Karachi Port Trust joined hands with KW&SB and shared 33% cost of S-III project as per approved PC-I. Moreover, KPT planned to built waste water treatment Plant at Mai Kolachi which will treat 60 mgd coming from Nehr-e-Khayyam, Soldier Bazar Nallah & City Railway Station Nallah.
The Karachi Port Trust and a non-profit environmental group known as PANI (Peoples & Nature Initiative) presented a viable solution for the treatment of waste water coming through these drains. The study was carried out by the professionals in the area which concluded that there are 17 small drains also pouring untreated liquid waste into the China Creek along with Nehr-e-Khayyam, Soldier Bazar Nallah & City Railway Station Nallah.
The solution presented is based on up-flow anaerobic sludge blanket concept. It is planned that Deep Septic Tank will be constructed at the site through which the sewage flows upward from the bottom and a thick sludge layer acts as a blanket to promote anaerobic degradation. This process will remove 80% bio-chemical oxygen demand from the water. The water coming from the septic tanks will allow to flow in a pond through open arteries for further refining. This treated water will overflow from the pond to the wetland where mangroves vegetation will clear it more before it enters into the harbour water. Various pathways and wildlife aviary will be established for promoting wide variety of environmental and ecological education activities.
Copyright Business Recorder, 2011