Nitrification, denitrification, and dephosphatation capability of activated sludge during co-treatment of intermediate-age landfill leachates with municipal wastewater

ABSTRACT

This study focuses on the possible use and efficacy of the co-treatment of landfill leachate (intermediate-age) with municipal wastewater. The nitrification, denitrification, and dephosphatation capability of activated sludge acclimated with a mixture of raw municipal wastewater (RWW) with gradually increasing amounts of raw landfill leachate (RLL) (from 0.5 to 5% v/v) were tested. Biochemical tests were conducted simultaneously in batch reactors (BRs). According to the obtained data, the ammonia utilization rate (AUR) was 3.68 g N/(kg volatile suspended solids (VSS)·h) for RWW, and it increased to 5.78 g N/(kg VSS·h) with the addition of 5% RLL. The nitrate utilization rate under anoxic conditions (NUR_AX) remained at a comparable level of 1.55–1.98 g N/(kg VSS·h). During the anoxic phase, both nitrate utilization and phosphorus uptake occurred, suggesting that denitrifying phosphorus-accumulating organisms (DPAOs) utilized N–NO₃. With the addition of RLL, the rates of anoxic and aerobic phosphate uptake (PUR_AX and PUR_AE) and phosphate release rate (PRR) decreased. The PRR was likely negatively influenced by high N–NO₃ concentrations but not completely inhibited due to the availability of a biodegradable fraction of chemical oxygen demand (COD). Thus, monitoring the NH₄–N load in wastewater treatment plant influent before co-treatment is more informative than that using hydraulic-based criteria.

Abbreviations: σ – standard deviation; AUR – ammonia utilization rate; DPAO – denitrifying phosphorus-accumulating organisms; MLVSS – mixed liquor volatile suspended solids content; MSW – municipal solid waste; NUR_AE – nitrate production rate under aerobic conditions; NUR_AX – nitrate utilization rate under anoxic conditions; PAO – phosphorus-accumulating organisms; PRR – phosphate release rate under anaerobic conditions; PUR_AX – phosphate uptake rate under anoxic conditions; PUR_AE – phosphate uptake rate under aerobic conditions; RLL – raw landfill leachates; RM0.5 – raw mixture of RWW with 0.5% (vol.) of RLL; RM3 – raw mixture of RWW with 3% (vol.) of RLL; RM5 – raw mixture of RWW with 5% (vol.) of RLL; RWW – wastewater; VFA – volatile fatty acids; WWTP – wastewater treatment plant

KEYWORDS:

• Intermediate-age landfill leachates
• municipal wastewater
• co-treatment
• kinetics of biochemical processes
• nitrification–denitrification–dephosphatation

Additional information

Funding

This research was co-financed by the following projects: The Polish Ministry of Science and Higher Education (Warsaw, Poland) [grant no. N N523 557538] and ‘The Centre for Advanced Studies – the development of interdisciplinary doctoral studies at the Gdansk University of Technology in the key areas of the Europe 2020 Strategy’ [POKL04.03.00-00-238/12].