Mumbai university > Civil > SEM 8 > Industrial Waste Treatment

Marks: 10M

Year: Dec 2014,

The modification in conventional aerobic and anaerobic biological treatment methods are as follows:

Oxidation ditch:

• The oxidation ditch involves the construction of number of ditch channels placed together side by side having depth of about 1.5m and length from 150-1000m or so.

• It may either consist of earthwork or in brick or stone masonry with vertical walls.

• The quality of effluent is quite good with suspended solids removal at about 95.4% and BOD removal about 98%

• This method however requires skilled supervision.

• It can be advantageously used for treating waste water from industries like pharmaceuticals, tanning, dairy etc located in densely populated area.

Oxidation pond:

• In oxidation pond, symbiosis relation exists between bacteria and algae.

• During day time in presence of O2, during photosynthesis process, this O2 is used by bacteria for oxidation of organic matter.

• In turn, bacteria will generate their own cell mass and CO2 is ultimate product of this oxidation process by algae.

• Depth of pond is maintained from 0.5-1m so that aerobic condition is maintained and also sunlight can reach upto bottom of ground.

• BOD removal ranges from 75-80%. It is necessary to give further treatment.

Aerated lagoons:

• An aerated lagoon is an earthen basin about 2.5-4m deep in which sludge sewage is filled and aerated by means of diffused air or mechanical aeration. Commonly mechanical aerators can be used.

• They are firmly fixed on permanent foundation. Sewage is sent in these lagoons after passing the grit chamber into giving any primary treatment.

• The detention period of 3-5 days is provided.

• It is ideally suited for middle size towns. The waste water of industries such as paper standard and food industries can also be easily treated by aerated lagoon.

• Due to increased depth they require shorter detention time i.e. 1/8-1/10 of these required for stabilization pond.

• The oxygen capacity varies from 1.5-2.5 kg of O2/lit/hr at 20 degree Celsius.

• The values vary depending on the characteristics of the sewage.