Fate ofCryptosporidiumoocysts,Giardiacysts, and microbial indicators during wastewater treatment and anaerobic sludge digestion

1999 ◽  
Vol 45 (3) ◽  
pp. 257-262 ◽  
Author(s):  
Christian Chauret ◽  
Susan Springthorpe ◽  
Syed Sattar
Keyword(s):  
Wastewater Treatment ◽  
Clostridium Perfringens ◽  
Heterotrophic Bacteria ◽  
The Other ◽  
Anaerobic Sludge ◽  
Somatic Coliphages ◽  
Aerobic Wastewater Treatment ◽  
Sludge Digestion ◽  
Cryptosporidium Oocysts ◽  
Anaerobic Sludge Digestion

The extent of reduction in selected microorganisms was tested during both aerobic wastewater treatment and anaerobic digestion of sludge at the wastewater treatment plant in Ottawa to compare the removal of two encysted pathogenic protozoa with that of microbial indicators. Samples collected included the raw wastewater, the primary effluent, the treated wastewater, the mixed sludge, the decanted liquor, and the cake. All of the raw sewage samples were positive for Cryptosporidium oocysts and Giardia cysts, as well as for the other microorganisms tested. During aerobic wastewater treatment (excluding the anaerobic sludge digestion), Cryptosporidium and Giardia were reduced by 2.96 log10and 1.40 log10, respectively. Clostridium perfringens spores, Clostridium perfringens total counts, somatic coliphages, and heterotrophic bacteria were reduced by approximately 0.89 log10, 0.96 log10, 1.58 log10, and 2.02 log10, respectively. All of the other microorganisms were reduced by at least 3.53 log10. Sludge samples from the plant were found to contain variable densities of microorganisms. Variability in microbial concentrations was sometimes great between samples, stressing the importance of collecting a large number of samples over a long period of time. In all cases, the bacterial concentrations in the cake (dewatered biosolids) samples were high even if reductions in numbers were observed with some bacteria. During anaerobic sludge digestion, no statistically significant reduction was observed for Clostridium perfringens, Enterococcus sp., Cryptosporidium oocysts, and Giardia cysts. A 1-2 log10reduction was observed with fecal coliforms and heterotrophic bacteria. However, the method utilized to detect the protozoan parasites does not differentiate between viable and nonviable organisms. On the other hand, total coliforms and somatic coliphages were reduced by 0.35 log10and 0.09 log10, respectively. These results demonstrate the relative persistence of the protozoa in sewage sludge during wastewater treatment.Key words: Cryptosporidium, Giardia, indicators, wastewater, sludge.

Energy self-sufficient sewage wastewater treatment plants: is optimized anaerobic sludge digestion the key?

2013 ◽  
Vol 68 (8) ◽  
pp. 1739-1744 ◽  
Author(s):  
P. Jenicek ◽  
J. Kutil ◽  
O. Benes ◽  
V. Todt ◽  
J. Zabranska ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Energy Consumption ◽  
Anaerobic Digestion ◽  
Biogas Production ◽  
Treatment Plant ◽  
Anaerobic Sludge ◽  
Waste Activated Sludge ◽  
Sludge Digestion ◽  
Anaerobic Sludge Digestion ◽  
Standard Energy

The anaerobic digestion of primary and waste activated sludge generates biogas that can be converted into energy to power the operation of a sewage wastewater treatment plant (WWTP). But can the biogas generated by anaerobic sludge digestion ever completely satisfy the electricity requirements of a WWTP with ‘standard’ energy consumption (i.e. industrial pollution not treated, no external organic substrate added)? With this question in mind, we optimized biogas production at Prague's Central Wastewater Treatment Plant in the following ways: enhanced primary sludge separation; thickened waste activated sludge; implemented a lysate centrifuge; increased operational temperature; improved digester mixing. With these optimizations, biogas production increased significantly to 12.5 m3 per population equivalent per year. In turn, this led to an equally significant increase in specific energy production from approximately 15 to 23.5 kWh per population equivalent per year. We compared these full-scale results with those obtained from WWTPs that are already energy self-sufficient, but have exceptionally low energy consumption. Both our results and our analysis suggest that, with the correct optimization of anaerobic digestion technology, even WWTPs with ‘standard’ energy consumption can either attain or come close to attaining energy self-sufficiency.

scholarly journals Short-term flexibility for energy grids provided by wastewater treatment plants with anaerobic sludge digestion

2019 ◽  
Vol 81 (7) ◽  
pp. 1388-1397 ◽  
Author(s):  
M. Schäfer
Keyword(s):  
Wastewater Treatment ◽  
Renewable Energy ◽  
Business Models ◽  
Wastewater Treatment Plants ◽  
Operation Mode ◽  
Anaerobic Sludge ◽  
Sludge Digestion ◽  
New Business ◽  
Anaerobic Sludge Digestion ◽  
Flexible Plant

Abstract For a sustainable development of the energy sector – in the future – an additional potential of energetic flexibility as well as storage capacities will be required to compensate for fluctuating renewable energy production. The operation of energy systems will change and flexibility in energy generation and consumption will rise to become a valuable asset. Wastewater treatment plants (WWTPs) with anaerobic sludge digestion are capable of providing that needed flexibility, not only with their energy generators but also in terms of their energy consuming aggregates on the plant. Under these circumstances a methodical approach has been developed that can be used to select, evaluate and safely implement typical aggregates on WWTPs for flexible plant operation and the provision of energetic flexibility. Relevant key figures have been developed that reconcile requirements of the purification processes with technical-physical necessities as well as the demands of the energy market. Furthermore, restrictions and control parameters have been established which complement the developed key figures to ensure effluent quality. It was demonstrated that WWTPs are able to adapt their operation mode to external and internal requirements under controlled conditions. The existing flexibility is suitable for a variety of uses, and WWTPs in general are able to participate in today's and in future energy supply products and new business models. The results show that WWTPs have a significant potential to produce renewable energy and to provide energetic flexibility, which is needed to stabilize future renewable-energy-driven energy grids.

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