Ingemar Karlsson

Chemical Wastewater Treatment — Value for Money

The British often use the expression “value for money”. In this paper we will try to demonstrate that this expression is very valid for chemical wastewater treatment. Different aspects of wastewater treatment will be examined, such as: Treatment efficiency Area requirement Sludge production Cost Ecological impact.

Carbon Source for Denitrification from Pre-Precipitated Sludge

The organic matter not removed by gravity in a pre-sedimentation tank is in a stable suspension consisting of particles smaller than 0.1 mm. This stable suspension may be destabilized by using low molecular, positively charged metal salts such as polyaluminium sulphate or polyaluminum chloride. These salts are also able to form fluffy hydroxide flocs that can arrest the destabilized particles through general sweep coagulation. Large aggregates capable of being sedimentated are formed. Dissolved compounds like phosphorus are precipitated at the same time. Figure 1 shows that with an effective flocculant and with good initial mixing and floc formation, particles down to 0.1 µ may be destabilized, coagulated and removed from the wastewater (Levine et. al., 1985).

Use of Internal Carbon from Sludge Hydrolysis in Biological Wastewater Treatment

Chemical pretreatment changes the composition of wastewater by reducing the content of particulate organic matter. The resulting lower sludge production facilitates the nitrification. The pretreatment reduces the amount of carbon available for denitrification. To increase the denitrification capacity, the precipitated sludge can be hydrolysed into a readily degradable form and used as a electron donor.

Beneficial Use of Sludge from Sewage Plants and Water Works

Pure water is one of our most important assets today. Therefore there are increasing demands on water treatment. It is our responsibility to return the water to nature in the same condition as we borrow it.

Thermal Sludge Treatment to Decrease Sludge Volume and Recycle the Sludge to New Products

Pure water is one of our most important assets today, and that is why we place increasing demands on water treatment. The purer the water we wish to return to nature — from whom we borrowed it — the more impurities (sludge) we have to separate. Sludge is thus a growing problem, but only a problem if the impurities are not separated into their different components.