Pretreatment processes for the recycling and reuse of sewage sludge

This paper focuses on mechanical disintegration and will compare its result s to thermal and ozone treatment. Several mechanical methods can be used fo r disintegration of sewage sludge. The methods differ in energy consumption and suitability of the machines for practical application, which is of gre at influence on the selection of the method. Thermal disintegration process es have a higher energy consumption than mechanical methods, but they can u se low cost thermal energy instead of electrical energy. The highest soluti on of organic components is achieved using ozone treatment. Several reuse o ptions of disintegrated sludge in aerobic and anaerobic processes are expla ined. An acceleration and enhancement of the anaerobic stabilisation proces s is observed, especially if excess sludge is used. Mechanical disintegrati on leads to better results than thermal treatment in the range of 60 to 130 degreesC. For the aerobic process the substitution of external proton dono rs is of special interest. High denitrification rates can be achieved, if t he sludge is adapted to the substrate. Increasing the concentration of nitr ogen and phosphorus in the supernatant, in order to recycle these valuable compounds, mechanical disintegration and ozone treatment seem to be more su itable than thermal disintegration.