Bacteriological evaluation of composting systems in sludge treatment (original) (raw)
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World Journal of Microbiology and Biotechnology, 2011
Changes in physical, chemical and microbial parameters were investigated during the composting of municipal sewage sludge. Raw sewage sludge (30% dry matter) was mixed with compost from sewage sludge (85% dry matter) in 3:1 ratio (v/v). The mixture was divided into 4 windrows which were composted under the same conditions except the turning factor. The turning was every 7, 10, 15 days and according to the temperature which must be (55-65°C) for windrow 1 (W1), windrow 2 (W2), windrow 3 (W3) and windrow 4 (W4), respectively. Water was added to adjust the moisture content (40-60%). The composting process consisted of 2 periods; fermentation (12 weeks) and maturation (4 weeks). The results showed that the temperature reached the maximum after 12 weeks for W1 and 11 weeks for W2, W3 and W4 and then decreased. The final compost was nearly odourless and black, especially in case of W4. The general trend indicates a decrease in organic matter, organic carbon and nitrogen (N), whereas ash, potassium (K) and phosphorus (P) increased and consequently C/K and C/P ratios decreased. There was a slight increase in C/N ratio. The pH increased and then decreased to near neutrality at the end. The mesophilic bacteria increased during the fermentation period and decreased after that, whereas the thermophilic ones increased with increasing of temperature, decreased after 2 weeks and increased again during the fermentation period and then decreased. The mesophilic and thermophilic fungi were present during the first week and disappeared after that. The final compost was pathogens-free as indicated by the counts of coliforms and Salmonella.
IOP Conference Series: Earth and Environmental Science, 2019
Jambi City has a Sludge Treatment Plant (IPLT) located in Talang Bakung. IPLT Talang Bakung processes sludge from household septic tanks. The processing consists of 1 anaerobic pond, 3 facultative ponds and 3 maturation ponds. The result of processing at IPLT is water that can be discharged into water bodies and sludge. The sludge still can be used, but it must be processed first. One of the sludge processing is a composting process. The composting process consists of two types, namely the composting process aerobically and anaerobically. This study aimed to compare the results of aerobic and anaerobic composting from IPLT sludge mixed with organic matter. Compost characteristics that are reviewed in this study are physical characteristics, those are water content and biological characteristics, namely pathogenic bacteria. The parameters measured in this study were the temperature, pH and number of Fecal Coliform bacteria at the beginning and end of the study
Purpose Sewage sludge samples from a water treatment plant in Nigeria were subjected to an in-vessel composting (using sawdust as a bulking agent) and thermal sludge processing to improve its quality for agricultural applications. Methods Treated samples were analyzed for physicochemical and microbiological properties using standard analytical and aerobic culture protocols. Results Microbiological analysis of the initial fresh mixture (sewage sludge/sawdust) showed that the total heterotrophic bacteria was 1.17 9 10 6 CFU/g of fresh compost, coliforms 4.7 9 10 4 CFU/g, Salmonella sp., and Shigella sp. 7.3 9 10 4 CFU/g, yeasts and moulds 9.0 9 10 4 CFU/g. These values were significantly (p = 0.05) reduced after 40 days of in-vessel composting to 4.3 9 10 4 CFU/g for total heterotrophic bacteria, 7.4 9 10 2 CFU/g for coliforms, while yeasts and moulds, Salmonella and Shigella sp. were not detected in the final compost. The results of the physicochemistry revealed variation in pH, temperature, and nutrients status of treated sludge. Conclusion Salmonella sp., Staphylococcus aureus, and Shigella sp. were eliminated, while a 2-log reduction in coliform counts occurred after 40 days of composting. Composting had a better processing impact by increasing the ash as well as reducing the carbon/nitrogen ratio of treated sludge, while thermal processing improved the sulfate and phosphate components of treated sludge. The treated sludge (biosolids) met the permissible limits of microbiological and nutritional standards recommended by US EPA for land application of sludge and could, therefore, be used as a biofertilizer, soil conditioner and also for land reclamation.
Environmental Technology & Innovation, 2021
Composting is a suitable solution to reduce the high quantity of sewage sludge produced every year. Microbiological quality of compost should be evaluated before its use. In this circumstance, researching the faecal bacteria indicators becomes more interesting to confirm the compost safety in terms of pathogenic microorganisms, which can cause health risk for the soil-plant-human system. This work monitored the evolution of pathogenic bacteria (faecal coliforms, faecal streptococci, Shigella spp., and Salmonella spp.) during windrows co-composting of three mixtures with different proportion of lagooning sludge and green waste under semi-arid climate. It also investigated the evolution of two bacteriophages (Coliphages and Salmonellaphages) as an indicator of long-term compost hygienization. The final composts showed a high reduction that reached 99% for faecal coliforms, faecal streptococci; and 100% for Shigella spp. and Salmonella spp.. These reductions revealed the efficiency of composting on bacteria inactivation. Comparison between the survivals of the two bacteriophages showed that Salmonella-phages have less tolerance to inactivation than coliphages, it was totally eliminated after 45 days of composting, while coliphages were completely inactivated after 200 days. The complete destruction of the bacteriophages showed the safety and the good microbial quality of the three cocomposting trials. These findings revealed that in the case of composting on windrows, a maximum temperature about 50 °C and time which, exceeds 5 months are essential to decrease pathogenic bacteria and virus to a safe level. We conclude that co-composting conditions of mixtures containing half and one-third of the sludge were more adequate for a rapid destruction of pathogens, compared to mixture containing two-third of the sludge. Based on this study, we anticipate that the proposed analysis will yield a rapid indicator of co-composting hygienization design with less dependency simple and fast technique.
STUDIES ON MICROBIOLOGICAL AND PHYSICOCHEMICAL CHANGES DURING WASTES COMPOSTING
Composting is one of the most successful biological processes for treatment of wastes residues. Microorganism’s activity during composting of waste materials were influenced by initial carbon/nitrogen ratios and physicochemical changes, e.g., electrical conductivity, temperature, pH, organic matter (OM) degradation, and total nitrogen (TN) losses. Compost heap was formed from mixture of rice straw, sugar beet straw and chicken manure. Also, total count of bacteria, fungi, actinomycetes, detection of pathogenic bacteria such as total and faecal coliform bacteria and salmonella were determined. Some physical and chemical analysis of compost during process was determined to determine compost maturity such as phytotoxicity and nitrification index. Thermophilic phase during composting process was decreased numbers of pathogenic microorganisms and after one month disappeared. Also, at the end of process E.C values were decreased after 4 months and germination index recorded 88.1% for maturity of compost.
Aspects Regarding Recycling Sludge by Composting\
Environmental Engineering and Management Journal
It has been an increased interest in using sewage sludge as agricultural fertilizer and soil improvement material, especially as compost with biomass. This paper analyses five samples of composts from bio waste and sewage sludge, with various percentage of sludge, using the following parameters: pH, EC, carbohydrates content, enzymes content and C: N ratio. The results were correlated with FT-IR spectra and germination test in order to assess the stability and maturity of the composts samples. It was also calculated the composition efficiency of compost samples. All tests indicate a favorable environment for microorganisms and a good conversion to complex compounds: amino acids, carbohydrates and products of their biodegradation amines, amides, carboxylic acids, aldehydes, ketones, enzymes, proving they can act as bio fertilizers.
Journal of Applied Sciences and Environmental Management, 2009
Environmental specialists classified sewage sludge as a hazardous waste because of high organic compounds and pathogenic microorganisms. Therefore sewage sludge should be stabilized before disposal. Composting is an effective and economical method to stabilize sewage sludge. The object of this study is determining the optimum conditions of co-composting of dewatered sewage sludge and sawdust. Pilot scale study was performed in Isfahan municipal wastewater treatment plant. To perform this study, the dewatered sewage sludge with humidity between 78-82 percent was mixed with sawdust. Turning over did once a week for aeration. Temperature was monitored at different depths daily. Other parameters such as N, C, organic matters, pH, heavy metals, total and fecal Coliform and Salmonella were determined three times a week. The results of this study showed that after about 15 th days, temperature of the mixture reached up to 55 o C, and was stabled for fifteen days. Humidity, organic matter, organic carbon and C/N ratio of the mixture decreased during of the study, due to increasing the temperature. Also organic matter and humidity mainly decreased in thermophilic phase. The number of total and fecal coliforms and also Salmonella decreased to A class standards of U.S. EPA at the end of the operation. The result indicated that co-composting of sewage sludge with sawdust is a reliable and simple method to schedule, with high flexibility and low odor production. Organic compounds and pathogenic microorganisms reduced and EPA standards were met during this method. @ JASEM .
Environmental Systems Research, 2017
Background: Composting is one of the integrated waste management strategies used for the recycling of organic wastes into a useful product. Composting methods vary in duration of decomposition and potency of stability, maturity and sanitation. This study was aimed to investigate the comparative effectiveness of four different methods of composting viz. windrow composting (WC), Vermicomposting (VC), pit composting (PC) and combined windrow and vermicomposting (WVC) on the stabilization, maturation and sanitization of mixtures of municipal solid organic waste and dried faecal sludge. Methods: The composting treatments were arranged in a completely randomized block design with three replications. The changes in physico-chemical and biological characteristics of the compost were examined at 20 days interval for 100 days using standard laboratory procedures. The analysis of variance was performed using SAS software and the significant differences were determined using Fisher's LSD test at P ≤ 0.05 level. Results: The evolution of composting temperature, pH, EC, NH + 4 , NO − 3 , NH + 4 : NO − 3 ratio, OC, C:N ratio and total volatile solids varied significantly among the composting methods and with composting time. The evolution of total nitrogen and germination index also varied significantly (P ≤ 0.001) with time, but their variation among the composting methods was not significant (P > 0.05). Except for PC, all other methods of composting satisfied all the indices for stability/maturity of compost at the 60th day of sampling; whereas PC achieved the critical limit values for most of the indices at the 80th day. A highly significant differences (P ≤ 0.001) were noted among the composting methods with regard to their effectiveness in eliminating pathogens (faecal coliforms and helminth eggs). The WVC method was most efficient in eliminating the pathogens complying with WHO's standard. Conclusion: Turned windrow composting and composting involving earthworms hastened the biodegradation process of organic wastes and result in the production of stable compost earlier than the traditional pit method of composting. The WVC method is most efficient in keeping the pathogens below the threshold level. Thus, elimination of pathogens from composts being a critical consideration, this study would recommend this method for composting organic wastes involving human excreta.
Characterization of bacterial population during composting of municipal solid waste
Composting is a natural biological process that degrades organic matter which is carried out spontaneously by aerobic microorganisms, whose metabolic action leads to the mineralization and partial humification of organic residue. The aim of this study was to investigate survival of potentially pathogenic bacterial species throughout the process and detection of enterotoxigenic Escherichia coli (ETEC) in the compost using PCR. The presence of heterotrophic bacteria, total total and fecal coliforms, and bacteria succession were also determined. Out of the total 222 bacterial colonies isolated, 33 different genera and 56 different species were identified, being Bacillus, Escherichia, Enterobacter, and Pseudomonas, the prevailing genera. Total coliform counts ranged between 9.0 x 10 4 and 3.0 x 10 6 cfu/g, and fecal coliform counts between 1.0 x 10 4 and 2.3 x 10 6 cfu/g. The composting process was partially efficient, since even though coliform counts were reduced, enterotoxigenic E. coli was detected in mature compost.
2016
ORIGINAL ARTICLE Introduction: The presence of pathogenic microbial agents and pathogens in organic fertilizers causes health problems and disease transmission. The aim of this study was to evaluate the efficiency of vermicomposting process in improve the microbial quality of the compost produced. Materials and Methods: This experimental study was conducted as a pilotscale one, in the laboratory of school of Health. In order to produce vermicompost, some perishable domestic waste were mixed whit sludge of wastewater treatment plant in a reactor. Tests to determine the microbial quality of the product were carried out at an early stage, during the process of production, and on the final product. The worms used for the production of vermicompost were Eiseniafotida worms. Results: According to the results of this study, a significant decrease was observed in the number of fecal coliforms in Sludgedomestic waste; as the number of fecal coliforms reduced from 7500000 (MPN/g), in the raw ...