No abstract

An innovative and patented process for medium-high strength sewage which comprises an anaerobic step followed by a hybrid anoxic-aerobic chamber and a final ultrafiltration stage was characterized in terms of methane fugitive emissions as well as odours. The operation at ambient temperature implies higher methane content in the liquid anaerobic effluent, which finally causes concentrations around 0.01-2.4% in the off-gas released in the anoxic-aerobic chamber (1.25% average). Mass balances indicate that these emissions account for up to 30-35% of the total methane generated in the anaerobic reactor. A conventional biofilter (BF) operated at an empty bed residence time of 4 min was used to treat these emissions for 70 d. In spite of the fluctuations in the methane inlet concentrations derived from the operation of the wastewater treatment plant (WWTP), it was possible to operate at pseudo-steady-state conditions, achieving average removal efficiencies of 76.5% and maximum elimination capacities of 30.1 g m(-3) h(-1). Odour removal was quantified as 99.1%. Fluorescence in situ hybridization probes as well as metabolic activity assays demonstrated the suitability of the biomass developed in the WWTP as inoculum to start up the BF due to the presence of methanotrophic bacteria.

The occurrence of endotoxins in the effluents generated in a full‐scale conventional activated sludge (CAS) wastewater treatment plant was studied, with values up to 843 EU mL−1, which might suppose an important threat to the environment and, if water reuse is considered, event to potential consumers. The use of advanced wastewater treatment technologies such as membrane biological reactors (MBRs), which combines biological process and membrane filtration, is a suitable alternative to minimize these biological micropollutants, thus allowing significant reductions in final effluents (lower than 100 EU mL−1 in this work). Different post‐treatment alternatives were applied to the secondary effluent of the full‐scale CAS plant such as tertiary membrane filtration (TMF), coagulation‐flocculation (CF), adsorption with activated carbon and ozonation. Results indicate that CF and TMF are the best options to minimize the presence of endotoxins in the final effluent (>90% and up to 72%, respectively). The use of powdered activated carbon was not so effective (8–30%) even after a prolonged contact time of 24 h. Finally, ozonation appears not to be adequate due to the low removal efficiencies achieved (40% maximum) as well as the potential generation of more endotoxic material, especially at contact times below 30 min. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 432–436, 2015