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Q&As since 1989


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Modification of biological waste water treatment plant

2005

We are a Korean Nylon Dyeing Finishing Industry operating in Bangladesh. We have a full fledged effluent treatment plant which enables us to thoroughly treat waste water from our dyeing mill and comply with international standard with regards to the treated effluent that we discharge.

Some of the dyestuff and chemicals that we use contain heavy metals like Cadmium(Cd) ; Chromium (Cr) ; Lead (Pb) ; Nickel (Ni) ; Zinc(Zn) and Copper(Cu). These heavy metals finally appear in the solid sludge which comes out of the treatment plant. Finally this sludge is disposed as landfill. Our concern is heavy metals may eventually leach out of the sludge and contaminate ground water.

We want your help with regard to the following.

1. Stabilization: How we may render the heavy metals stable so that it is insoluble to water and do not leach out to the ground water.
2. Immobilization: How we may immobilize/contain the sludge so that metals do not leach out.
3. Detoxification: How we may separate out the heavy metals and detoxify the sludge.

We are also interested in reducing usage of chemicals (e.g. alum) and amount of sludge generated.

May be any or a combination of the above options would be the solution to our problem.

MOHAMMAD IFTIKHER HAIDER
- Dhaka , Bangladesh

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Leaching of metals from sludges can be greatly reduced by blending the sludge with a "pozzolanic" material such as cement or fly ash. Some areas use clay soil such as laterite, but I do not know its effectiveness. The material should be mixed thoroughly, preferably in a mixer-muller or plow blender, so that there are no large pieces remaining. The metals are probably not worth recovering is you are using large quantities of alum.

Paul Morkovsky
- Shiner, Texas, USA
2005