Hygienization performances of innovative sludge treatment solutions to assure safe land spreading (original) (raw)
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Hygienization by innovative sludge treatment processes, to assure safe land spreading
Sludge microbial quality is a major issue to be assessed for the sustainable reuse of sludge in agriculture. Within the ROUTES project innovative solutions for the production of good quality sludge are evaluated and the hygienisation performances of the proposed sludge treatment systems is assessed. The paper describes the efficiency of pathogens and indicator removal by a combination of a disintegration pre-treatment, by thermal hydrolysis, and thermophilic anaerobic digestion and by a combined anaerobic and aerobic digestion process. To better address the fate of pathogens with diverse resistance capacity different indicators microorganism (E.coli, spore of sulphide reducing clostridia SSCR and somatic coliphage SOMCPH) and specific pathogens (Salmonella and enteric viruses) were monitored. An improvement of hygenization was obtained by both investigated processes. Thermal pre-treatment improved the SOMCPH removal of more than one logarithmic unit and efficiently eliminated bacter...
Monitoring of bacterial and parasitological contamination during various treatment of sludge
Water Research, 2001
Abstract}Wastewater treatment results in the production of large quantities of sludge. Agricultural use is an interesting alternative provided that the health risks are taken into account. In France, a decree (1998) defines ''sanitized'' sludge as sludge that has been treated so that pathogens (Salmonella, enteroviruses, viable nematode eggs) are no longer detectable. The aim of this study was to determine the impact of various sludge treatments on 2 types of pathogens (Salmonella and nematode eggs). We also assessed the levels of micro-organisms that indicate faecal contamination (E. coli, Enterococci, sulfite-reducing anaerobes spores). Various treatment processes were analyzed: 4 biological, 3 chemical, 1 heat , 2 storage and 4 sampling campaigns were carried out. Concerning the parasitological contamination of sludge at the entrance of all sites, concentrations of total nematode eggs and viable nematode eggs were highly heterogeneous (respectively, from 2 to 53 eggs/10 g DM and from 2 to 45 eggs/10 g DM) with viable eggs present in all samples. The total concentration of nematode eggs in the sludge was not greatly affected by treatment or storage, and was in the range 51-66 eggs/10 g DM. However, the situation was different for mean viable egg counts. For four treatments, no viable eggs were detected. Mesophilic processes are inefficient at eliminating viable nematode eggs. Salmonella were systematically detected in all sludge samples at the entry to the station, except for limed sludge intended for storage. At the end of four treatments Salmonella had been totally eliminated. For the fecal contamination indicators, the largest decrease in E. coli contamination was observed following liming and after thermophilic treatment. The mesophilic treatments resulted in very small decreases in contamination. A similar pattern was observed with Enterococci. For the spores of sulfite-reducing anaerobe bacteria, with the exception of heat treatment, which reduced contamination by 3.2 log units, the maximum decrease in contamination was 1.7 log. For storage of sludge, E. coli and Enterococci levels had decreased at first but then increased between 6 and 8 months of storage. #
Hygienization of sludge through anaerobic digestion at 35, 55 and 60 °C
Water Science & Technology, 2013
Legislation in Sweden and the European Union concerning the use of sewage sludge in agriculture is under revision and future concentration limits for pathogens in treated sludge are likely to be expected. The aim of this study was to evaluate the hygienization of Salmonella, Escherichia coli, Enterococcus and Clostridium perfringens through continuous anaerobic digestion at 35, 55 or 60 °C, as well as to investigate process stability and methane production at 60 °C. The results indicated that digestion at 55 or 60 °C with a minimum exposure time of 2 h resulted in good reduction of Salmonella, E. coli and Enterococcus and that anaerobic digestion could thus be used to reach the concentration limits suggested for the EU, as well as Sweden. Furthermore, stable continuous anaerobic digestion of sludge was achieved at 60 °C, albeit with 10% less methane production compared to digestion at 35 and 55 °C.
Microbiological quality of sewage sludge after digestion treatment: A pilot scale case of study
Journal of Cleaner Production, 2020
In the frame of the water circular economy, the reuse of the treated sewage sludge supposes a good action. Nevertheless, the reuse might suppose a human health risk because of the presence of pathogen germs, concentrated in the generated sludge during urban wastewater treatment. For this reason, sludge treatments, conventional or advanced, should be focused on the reduction of fermentation capacity and microorganisms presence. This research assess the microbiological quality of the treated sludge, based on the use of faecal pollution indicators such as total coliforms, Escherichia coli, Enterococcus sp., Pseudomonas sp., Staphylococcus aureus and total mesophilic bacteria, after the application of different digestion treatments, and their final aptitude to be reused. Three different pilot scale plants were used: two anaerobic digestion plants with a volume of 2.75 m 3 working in mesophilic (35-37 C) and thermophilic (55-57 C) conditions, and hydraulic retention times (HRT) ranging from 5 to 20 days; and a autothermal thermophilic aerobic digestion plant (ATAD) with a volume of treatment of 3.9 m 3 working at 55-57 C for an HRT of 5e15 days. The raw sludge to be treated came from a full-operative WWTP located in the region of Navarra (Spain), laid within Ebro River Basin. It was concluded that both treatments studied obeyed the current European legislation in therms of E. coli concentration and absence of Salmonella spp., being available for agricultural purposes. Considering other microbiological parameters, the anaerobic thermophilic treatment had the best conditions to reduce the Enterococcus sp. concentrations and the aerobic thermophilic treatment was the best one reducing E. coli, being non-significant the influence of HRT to microbial reduction. For this reason, it is strongly recommended the use of both faecal indicators to assess the microbial quality of the treated sludge.
The importance of Evaluation of microorganisms in raw sewage sludge intended for agriculture
Research Square (Research Square), 2024
The present study was conducted to determine the microbiological characteristics of sewage sludge from ve waste-water treatment plants (WWTPs) in eastern Algeria and to assess the e ciency of drying beds in lowering the microbial load in this sludge, which is typically used in agricultural elds. We chose the ve most signi cant waste-water treatment facilities in Algeria's Eastern area to carry out this study. Where we have counted harmful microorganisms (Salmonella, Clostridium), and examined parasites. Total coliforms, fecal "E. coli" and fecal streptococci were used as indicators of fecal contamination. The obtained results indicate that the examined sewage sludge is a rich source of microorganisms, particularly bacteria of fecal origin, especially during the months of high temperature (Spring, Summer), and moor particular in the sludge of medium age (more than 1 month). As a result, we have reported a signi cant presence of anaerobic sulfate-reducingria (ASR), Salmonella spp., and E. coli. We also observed that this sludge included parasites, ranging from protozoa to helminth eggs. We may draw the conclusion that even if the microbiological load in the sewage sludge signi cantly decreased after treatment in the drying beds, the hazards associated with the spread of this sludge must be managed by adherence to a set of exact guidelines. This study allowed us to determine the microbiological properties of sewage sludge, through which we can reduce the risks or de nitively eliminated, which allows the possibility of valued them in the agricultural sector by avoiding all possible environmental risks and even on health public.
Microbiological Control in Decontamination of Sludge from Wastewater Treatment Plant
Processes, 2022
Dynamics of the microbiological indicators of fresh sludge from wastewater treatment plants with a concentration of CaO, 10% and 20%, and ash, −30% and 50%, and treated with quicklime, ash, and microbial fertilizer for a 50-day period of composting were studied. The influence of temperature, water content, and oxygen on the development of microbes was established in laboratory conditions. Microbiological analysis included the determination of non-pathogenic (non-spore-forming bacteria, bacilli, actinomycetes, micromycetes, bacteria digesting mineral nitrogen), and pathogenic (Salmonella, Listeria, Escherichia coli, Enterococcus, Clostridium perfringens) microorganisms. Of the beneficial microflora in the sludge before treating, the amount of non-spore-forming bacteria was the highest, followed by bacilli and micromycetes. It was found that actinomycetes were absent in the untreated sludge. Clostridium perfringens occupied a major share in the composition of the pathogenic microflora...
Journal of Water and Health, 2015
Birkenhead and coliphage MS2 during 1 mesophilic anaerobic digestion and air drying of sewage sludge 2 3 4 ABSTRACT 21 Factors affecting the decay of Salmonella Birkenhead and coliphage, as representatives of 22 bacterial and viral pathogens, respectively, during mesophilic anaerobic digestion (MAD) and 23 air drying treatment of anaerobically digested sewage sludge were investigated. Controlled 24 concentrations of S. Birkenhead were inoculated into non-sterile, autoclaved, -irradiated 25 and nutrient-supplemented sludge and cultures were incubated at 37 ºC (MAD sludge 26 treatment temperature) or 20 ºC (summer air drying sludge treatment temperature). Nutrient 27 limitation caused by microbial competition was the principal mechanism responsible for the 28 decay of S. Birkenhead by MAD and during air drying of digested sludge. The effects of 29 protease activity (PA) in sludge on MS2 coliphage decay in digested and air dried sludge 30 were also investigated. MS2 coliphage showed a 3.0-3.5 log 10 reduction during incubation 31 with sludge-protease extracts at 37 °C for 25 h. Proteases produced by indigenous microbes 32 in sludge potentially increase coliphage inactivation and may therefore have a significant role 33 in the decay of enteric viruses in sewage sludge. The results help to explain the loss of 34 viability of enteric bacteria and viral pathogens with treatment process time, and contribute to 35 fundamental understanding of the various biotic inactivation mechanisms operating in sludge 36 treatment processes at mesophilic and ambient temperatures. 37 38
The Effect of Physical Factors on Fecal Coliform Viability Rate in Sewage Sludge
Journal of Geoscience and Environment Protection, 2014
Experiments were conducted on the survival rate of fecal coliform after spreading the sewage sludge for desiccation on sludge beds in an open field throughout the year. The ambient temperature, humidity, sunlight intensity and solar radiation were measured during the period of sludge desiccation. The maximum average temperature, sunlight intensity and solar radiation were recorded throughout the year. During May and August the minimum microbial counts were recorded after four weeks of sludge desiccation. Relative humidity did not have significant effect on survival rate. The minimum microbial counts were taken after four weeks of sludge drying. When the sludge was mixed with three different media, the maximum count of fecal coliform was presented when soil mixed with sludge and irrigated with treated sewage effluent (TSE). When soil mixed with sludge irrigated with well water, the number of fecal coliform count dropped significantly. The minimum count occurred when compost was used instead of sludge. This was a clear indication that the source of contamination was from sludge and was mostly contributed by the TSE irrigation. The use of dried sludge after four weeks of treatment had the lowest fecal coliform count and was safe to be used as fertilizer for farming. Oman is located in a semi-equatorial belt with arid environmental conditions which are ideal for elimination of microbial pathogens. Thus, sludge desiccation in such environmental conditions, specifically during the hot months of the year, is perfect for such practice.
Occurrence and levels of indicators and selected pathogens in different sludges and biosolids
Journal of Applied Microbiology, 2007
Aims: Determine the occurrence and levels of pathogens and indicators in raw and treated sludges and compare their persistence after two different treatments.Methods and Results: Helminth ova, Cryptosporidium spp., Salmonella spp., enteroviruses, and bacterial and viral indicators were determined in raw sludges and biosolids produced after mesophilic and thermophilic treatments. Except Salmonella, all of the parameters were quantified. Helminth ova were found at very low concentrations even in raw sludges. Viable Cryptosporidium oocysts were still present in most samples of treated sludges. Faecal coliforms, spores of sulphite-reducing clostridia (SSRC), and somatic coliphages were the only indicators with values above their detection limits in most of the samples.Conclusions: Pathogens were still detected in some treated sludge samples. SSRC were the most resistant micro-organisms to treatments and hence may be an indicator for the reduction of protozoan oocysts. Somatic coliphages constitute an alternative as viral indicators due to their detection in sludges before and after treatment.Significance and Impact of the Study: Because of the persistence of some pathogens after sludge treatments, additional indicators are needed. SSRC and somatic coliphages are good candidates. Easy and inexpensive methods for the determination of these indicators are feasible both in industrialized and developing countries.