Treatment procedure for fermentable sludge or effluent consists of reducing pH level, adding nitrite salt, agitating, filtering and neutralizing

摘要

The procedure for treating a fermentable sludge or effluent containing at least 15g/l of dry matter consists of extracting it from its reservoir and subjecting it to an acidification process with sulfuric acid to adjust its pH value to between about 2.5 and 3.5. A nitrite salt is then added to it to give a concentration of 0.5 - 1g of nitrogen per kg of dry matter, and the mixture is kept for a period of 5 min to 12 hours with constant or intermitted agitation, followed by the addition of a polymer and a filtering stage in a filter press to yield a filtrate and dehydrated sludge. The filtrate is passed through a buffer storage stage and then neutralized to about pH 7 immediately before discharging it into a reservoir. The residual sludge is compacted at a pressure of about 9 - 12 bars.