title: Persistency of bacterial indicators in biosolids stabilization with coal fly ash and lime.
abstract: Alkaline coal fly ash and lime were tested for their effectiveness in pathogen removal from biosolids at different time intervals and temperatures. Coal fly ash at 10 and 35% w/w was mixed with dewatered biosolids and then the ash-biosolids mixture was mixed separately with 0, 1.1, 2.2, 4.4, 8.5, 11, and 18% calcium oxide (w/w on a dry weight basis) with and without heating to 55 degrees C. Total bacteria, salmonella, and total coliforms were monitored at various time intervals. Both ash-biosolids mixtures with or without lime amendment had a significantly lower total bacterial population than the biosolids control, but the residual indigenous bacterial flora in the ash and lime stabilized biosolids still maintained a population of greater than 10(4) g(-1) dry biosolids. Alkaline-stabilized biosolids with a lime amendment rate greater than 8.5% could maintain pH greater than or equal to 12 for more than 2 hours, which effectively removed total coliforms and salmonella in the mixture. Heat treatment to 55 degrees C and a storage time of 14 days provided an added advantage resulting in a further reduction in pathogens for all treatments. It is recommended that 10% ash-biosolids mixture should be amended with a minimum of 8.5% lime on a dry weight basis for at least 2 hours to achieve acceptable levels of salmonella and total coliforms to ensure no pathogenic risk following land application.
authors.affiliation: Department of Biology, Hong Kong Baptist University, Peoples Republic of China. jwcwong@hkbu.edu.hk
authors.forename: J W
authors.initials: JW
authors.lastname: Wong
authors.forename: M
authors.initials: M
authors.lastname: Fang
authors.forename: R
authors.initials: R
authors.lastname: Jiang
mesh_terms: D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification; D017610:Calcium Compounds / Q000494:pharmacology*; D002244:Carbon / Q000494:pharmacology*; D011232:Chemical Precipitation; D003031:Coal; D060729:Coal Ash; D004755:Enterobacteriaceae / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D010087:Oxides / Q000494:pharmacology*; D052638:Particulate Matter; D012475:Salmonella / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification; D013997:Time Factors
chemical_list: D017610:Calcium Compounds; D003031:Coal; D060729:Coal Ash; D010087:Oxides; D052638:Particulate Matter; D002244:Carbon; C016538:lime