Disposal of Active Sludge from Wastewater Treatment Plants

Otpadnu vodu potrebno je obraditi prije ispuštanja u vodotokove. Proces obrade otpadnih voda obuhvaća provedbu prethodnih, primarnih, sekundarnih (bioloških) te tercijarnih postupaka. Iako biološka obrada otpadne vode može biti aerobna ili anaerobna, u praksi se češće susreće aerobna tehnologija obrade aktivnim muljem. Aerobnom obradom otpadne vode nastaju velike količine aktivnog mulja kojeg je potrebno zbrinuti na odgovarajući način. Postupci obrade mulja uključuju kondicioniranje, zgušnjavanje, odvodnjavanje, stabilizaciju, kompostiranje te toplinsku obradu. Obrađeni mulj moguće je konačno odložiti na zemljištu (lagune, ozemljavenjem), iskoristiti u poljoprivredi ili upotrijebiti kao sirovinu za dobivanje proizvoda termičkom oksidacijom (bioplin, solidifikacija). Izbor načina konačnog odlaganja mulja odraz je lokalnih, nacionalnih, kulturnih, povjesnih, geografskih, pravnih, političkih i ekonomskih okolnosti. Tako je najšire primjenjivana opcija konačnog odlaganja mulja u EU iskorištavanje mulja u poljoprivredi te odlaganje na odlagalištima, reklamacija i restauracija zemlje te spaljivanje. Obradu mulja treba smatrati sastavnim djelom postupka obrade otadnih voda. U radu su opisani navedeni postupci obrade i konačnog odlaganja mulja s naglaskom na anaerobnoj stabilizaciji.Before discharging into recipient, wastewater must be treated. Wastewater treatment includes previous, primary, secondary (biological) and tertiary treatment. Although biological treatment can be aerobic and anaerobic, the aerobic activated sludge technology is more commonly used. Downside of this technology is that large amounts of active sludge are produced, which should be managed properly. Excess sludge treatment processes include conditioning, concentration, drainage, stabilization, composting and heat treatment. Treated sludge can be disposed on landfills or in lagoons, used in agriculture or in thermal oxidation process for production of new products (solidification). Selection of final sludge disposal mode is reflection of local, national, cultural, historical, geographical, political and economic circumstances. In the EU, the most common disposal mode is exploitation of sludge in agriculture, its disposal on landfills, reclamation and restoration of ground or incineration. Sewage sludge treatment should be considered as a constituent part of wastewater treatment procedure. This paper describes different wastewater sludge treatments and its final disposal, with an accent on the anaerobic stabilization