Integral analysis of hydrodynamic cavitation effects on waste activated sludge characteristics, potentially toxic metals, microorganisms and identification of microplastics.

Wastewater treatment plants, the last barrier between ever-increasing human activities and the environment, produce huge amounts, of unwanted semi-solid by-product - waste activated sludge. Anaerobic digestion can be used to reduce the amount of sludge. However, the process needs extensive modernisation and refinement to realize its full potential. This can be achieved by using efficient pre-treatment processes that result in high sludge disintegration and solubilization. To this end, we investigated the efficiency of a novel pinned disc rotational generator of hydrodynamic cavitation. The results of physical and chemical evaluation showed a reduction in mean particle size up to 88%, an increase in specific surface area up to 300% and an increase in soluble COD, NH4-N, NO3-N, PO4-P up to 155.8, 126.3, 250 and 29.7%, respectively. Microscopic images confirmed flocs disruption and damage to yeast cells and Epistilys species due to mechanical effects of cavitation such as microjets and shear forces. The observed cell ruptures and cracks were sufficient for the release of small soluble biologically relevant dissolved organic molecules into the bulk liquid, but not for the release of microbial DNA. Cavitation treatment also decreased total Pb concentrations by 70%, which was attributed to the reactions triggered by the chemical effects of cavitation. Additionally, the study confirmed the presence of microplastic particles and fibers of polyethylene, polyethylene terephthalate, polypropylene, and nylon 6 in the waste activated sludge.

The Detection Rate of Enteric Viruses and Clostridium difficile in a Waste Water Treatment Plant Effluent.

Waste water treatment plant (WWTP) is considered as an important source of surface water contamination by enteric pathogens. In this study, we describe the occurrence of enteric viruses (group A rotaviruses, noroviruses, astroviruses, sapoviruses, hepatitis A virus, and hepatitis E virus) and Clostridium difficile in the effluent of a wastewater treatment plant during a 1-year period. Enteric viruses were simultaneously and efficiently concentrated in a single step using methacrylate monolithic chromatographic support. Rotaviruses, noroviruses (genogroup I and II), and sapoviruses were detected in all 12 concentrated samples, whereas astroviruses were not detected in August and September and hepatitis A and E viruses were not detected at all. Clostridium difficile was detected in all samples and altogether 121 strains were isolated and grouped into 32 different ribotypes of which 014/020 and 010 were most prevalent. Pathogens detected in WWTP effluent partially reflect the epidemiological situation of enteric viruses and C. difficile in human population and open the discussion on implementation of possible techniques for virus and bacteria removal from WWTP effluent prior to release into the surface water system.

Total bacterial and ammonia-oxidizer community structure in moving bed biofilm reactors treating municipal wastewater and inorganic synthetic wastewater.

Industrial-scale bioreactors treat wastewater of temporally variable composition under different weather conditions, while the microbial populations of wastewater treatment plants are often studied in controlled laboratory-scale systems with defined influent at a constant temperature. 16S rRNA- and ammonia oxidising amoA-gene-defined bacterial community structure was investigated in industrial and laboratory-scale moving bed biofilm bioreactors (MBBRs) treating municipal wastewater (WW) or synthetic ammonium solution (AS). Nitrification activity, 16S rRNA and amoA gene T-RFLP profiles were comparable between industrial and laboratory scale WW bioreactors. AS bioreactors exhibited higher nitrification and higher relative abundances of Nitrosomonadaceae and Nitrospiraceae families but only small changes in the general bacterial community structure was detected compared to WW MBBRs. Nitrosomonas europaea lineage dominated WW, while uncultivated Nitrosomonas-like sequences prevailed in AS bioreactors. These results suggest that influent type has a stronger influence on community structure than operational conditions, such as temperature or bioreactor size.