THE EFFECT OF A MODIFIED METHOD OF LIME-STABILIZATION SEWAGE-TREATMENT ON ENTERIC PATHOGENS

This study was conducted to demonstrate the effectiveness of a modific ation of lime stabilisation by the incorporation of pulverised fuel as h (PFA) for disinfection of sludge. The modified treatment is economic in terms of lime utilisation and uses another waste product, PFA, whi ch would also require disposal. Intestinal pathogens are the most prob able pathogenic organisms present in the sludge. Several species of in testinal pathogen were examined for their ability to survive in raw sl udge and then subjected to disinfection. The effect of the chemical mi xture was attributed to the high pH produced and maintained, as heat p roduction in the modified process was minimal. A mixture of 60% sludge (600 g/kg): 40% CaO/PFA (44.44 g/kg / 355.56 g/kg) with the ratio CaO :PFA 1:8, was shown to be able to prevent the growth of bacterial path ogens and maintain a pH above 11.0 for at least 7 d. Although further study concerning texture and other physical properties is required, a modified sludge treatment with this relatively low proportion of lime was found to be suitable for landfill or land reclamation as far as it s bacteriological disinfecting quality is concerned. (C) 1998 Elsevier Science Ltd.