E. Kulbat

Antimicrobial resistance of fecal indicators in disinfected wastewater

The main objective of the study was to assess the potential of three systems (UV irradiation, ozonation, and micro/ultrafiltration) operated in a pilot scale in removal of antimicrobial-resistant fecal bacteria from secondary effluent of the local wastewater treatment plant (700,000 population equivalent). The effectiveness of the processes was analysed using the removal ratio of fecal indicators (Escherichia coli and Enterococcus spp.). The susceptibility of fecal indicators to antimicrobial agents important in human therapy was examined. Resistance to nitrofurantoin and erythromycin was common among enterococci and followed by resistance to fluoroquinolones and tetracycline. Resistance to high-level aminoglycosides and glycopeptides was also observed. E. coli isolates were most frequently resistant to penicillins and tetracycline. The extended-spectrum beta-lactamase-producing E. coli was detected once, after ozonation. Substantial attention should be paid to the E. coli and enterococci resistant to three or more chemical classes of antimicrobials (MAR), which in general constituted up to 15 and 49% of the tested isolates, respectively. Although the applied methods were effective in elimination of fecal indicators (removal efficiency up to 99.99%), special attention has to be paid to the application of sufficient disinfection and operation conditions to avoid selection of antimicrobial resistant bacteria.

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 (NURAX) 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 (PURAX and PURAE) 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; NURAE – nitrate production rate under aerobic conditions; NURAX – nitrate utilization rate under anoxic conditions; PAO – phosphorus-accumulating organisms; PRR – phosphate release rate under anaerobic conditions; PURAX – phosphate uptake rate under anoxic conditions; PURAE – 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

Elimination of the Chemical and Microbiological Pollutants in the Modernized Wastewater Treatment Plant “WschóD” in Gdańsk

In the article the results of investigations concerning the performance of modernised wastewater treatment plant “Wschod” are presented. The MUCT reactors were introduced in the biological treatment stage. WWTP is equipped with a unit for volatile fatty acids generation from primary sludge. The results of 2-years investigations of the removal of chemical and microbiological pollutants and parasites are discussed. The basic technological problems during the operation of the WWTP are identified. The removal of bacteria and parasites at subsequent stages of sewage treatment is analysed.