Sludge Hygienization / Sludge Pasteurization
From Sludge Management
Equipment consists of recuperative exchanger, pasteurization exchanger and pasteurization container.Equipment works with undrained sludge with dry matter content 5 to 8 %.Non-treated sludge is preheated in recuperative exchanger with utilization of heat recovery from pasteurized sludge.Preheated sludge is warmed by heating water on given pasteurization temperature in pasteurization exchanger (water/sludge).Necessary detention period for sludge hygienization is achieved in pasteurization container.Pasteurization temperature guarantees devitalization of pathogenic microorganisms in given detention period.Pasteurized sludge is cooled down in recuperative exchanger by giving its heat to non-treated sludge before inlet to sludge digester.In mesophillic sludge digester originates energy-rich biogas.From biogas and its burning is received electric energy and warm.
Pasteurization is process, whereat sludge is warmed on certain temperature only for short time, e.g. on 70 °C for a period at least 30 minutes. Optimal temperature is 64 to 70 °C, which warrants high level of pathogenic microorganisms devitalization. Pasteurizaton must be combined with following sludge stabilization, in most cases anaerobic in sludge digester. It's because already weakened pathogens in reduced quantity aren't able to compete for substrate with anaerobic biomass in sludge digesters and they wither away in it. Another advantage of pre-pasteurized sludge is its better stabilization and better dewatering features.
Pasteurization process take place in 3 apparatuses: recuperative exchanger sludge/sludge, pasteurization exchanger water/sludge and pasteurization container. Non-treated sludge is pumped into inner chamber of recuperative exchanger. Outer chamber of recuperative exchanger is filled with warmed hygienized (pasteurized) sludge, which is pumped from pasteurization container. There is necessary to agitate inner chamber of recuperative exchanger. Thereby will take up place warm transfer between warm and cool sludge.
Preheated non-treated sludge is pumped into pasteurization exchanger water/sludge, where is heated on temperature 70 °C. That temperature must be keeped minimally for 30 minutes, whereof is achieved in pasteurization container. Keeping of needed temperature in pasteurization container is scaned by temperature meters in that container. There is supplied heating water with temperature 80 °C from boiler-room (or eventually from combined heat and power unit if it's installed) into pasteurization exchanger for sludge warming.
Pasteurized (hygienized) sludge is used again for preheating of new incoming sludge in recuperation exchanger. Pasteurized sludge is cooled by it and moves away to sludge digester, where passes sludge stabilization process.