Freezing/thawing effects on anaerobic digestion of mixed sewage sludge.
This study examined the effects of freezing/thawing disintegration on the characteristics of mixed (primary and waste) sewage sludge from municipal wastewater treatment plants. It also assessed the effects of freezing/thawing on anaerobic digestion, and its consequences for biogas production and digester supernatant quality. Freezing/thawing caused a decrease of more than 10% in the total chemical oxygen demand (COD), total nitrogen (TN), volatile solids (VS) and total solids (TS). A simultaneous doubling of the soluble COD and volatile fatty acids (VFA) occurred. Release of nitrogen and phosphorus compounds was also found. The biogas yield obtained from frozen/thawed sludge was 1.31 m(3) kg(-1) of removed VS; this exceeded approximately 1.5 times the value for the raw sludge. On the basis of the global mass balance it was indicated that freezing/thawing of the mixed sewage sludge followed by anaerobic digestion could be considered as a "double-phase digestion" rather than a pre-treatment method.
Montusiewicz
A
A
Institute of Environmental Protection Engineering, Faculty of Environmental Engineering, Lublin University of Technology, ul. Nadbystrzycka 40B, 20-618 Lublin, Poland. A.Montusiewicz@wis.pol.lublin.pl
Lebiocka
M
M
Rozej
A
A
Zacharska
E
E
Pawłowski
L
L
D000693:Anaerobiosis; D005615:Freezing; D005740:Gases; D012722:Sewage
D005740:Gases; D012722:Sewage