Distribution and persistence of fecal bacterial populations in liquid and dewatered sludge from a biological treatment plant

The changes in composition and structure of fecal coliforms (FC) and enterococci (ENT) populations, as well as the elimination of spores of sulphite-reducing bacteria (SRB), were compared between municipal sewage and their derived sludge in a biological treatment plant in order to determine any selective reduction or adsorption to sludge during the treatment process. Additionally, the persistence of antibiotic-resistant enterococcal populations in two kinds of sludge was also considered to evaluate their potential elimination in the treatment process. Microbial indicators, vancomycin-resistant and erythromycin-resistant enterococci were enumerated. The structure and composition of FC and ENT populations were determined by biochemical fingerprinting and clustering analyses. Raw and treated sewage showed a concentration of FC 1 log unit higher than ENT and nearly 2 log units higher than spores of SRB. However, the three studied indicators showed similar concentrations in both types of sludge. Consequently, FC were eliminated in higher proportion than ENT and spores of SRB in sludge. FC and ENT populations showed high diversity and similarity population indexes for all kinds of samples. Antibiotic-resistant enterococci persisted in a similar proportion in respect to total enterococci not only in treated sewage but also in sludge. The persistence of antibiotic-resistant strains in sludge as well as in treated sewage should be considered if they are used for land disposal or for water reutilization, respectively.     

Viability of Rhodococcus equi and Parascaris equorum Eggs Exposed to High Temperatures

There is great concern about the potential pathogen contamination of horse manure compost spread in the same fields horses graze in. To ensure that pathogen destruction occurs, temperatures need to be sufficiently high during composting. Here, we investigated the survival rate of two marker organisms, Rhodococcus equi and Parascaris equorum eggs, exposed to temperatures potentially encountered during horse manure composting. Our results show that the time required to achieve a 1 log10 reduction in R. equi population (D-value) are 17.1 h (±1.47) at 45°C, 8.6 h (±0.28) at 50°C, 2.9 h (±0.04) at 55°C and 0.7 h (±0.04) at 60°C. For P. equorum eggs we show that at 45 and 50°C, 2 log10 reduction of viability is reached between 8 and 24 h of incubation and that it takes less than 2 h at 55 and 60°C to achieve a viability reduction of 2 log10. These results are useful for identifying composting conditions that will reduce the risk of environmental contamination by R. equi and P. equorum eggs.     

Inactivation of animal viruses during sewage sludge treatment.

Using a previously developed filter adsorption technique, the inactivation of a human rotavirus, a coxsackievirus B5, and a bovine parvovirus was monitored during sludge treatment processes. During conventional anaerobic mesophilic digestion at 35 to 36 degrees C, only minor inactivation of all three viruses occurred. The k' values measured were 0.314 log10 unit/day for rotavirus, 0.475 log10 unit/day for coxsackievirus B5, and 0.944 log10 unit/day for parvovirus. However, anaerobic thermophilic digestion at 54 to 56 degrees C led to rapid inactivation of rotavirus (k' greater than 8.5 log10 units/h) and of coxsackievirus B5 (k' greater than 0.93 log10 unit/min). Similarly, aerobic thermophilic fermentation at 60 to 61 degrees C rapidly inactivated rotavirus (k' = 0.75 log10 unit/min) and coxsackievirus B5 (k' greater than 1.67 log10 units/min). Infectivity of parvovirus, however, was only reduced by 0.213 log10 unit/h during anaerobic thermophilic digestion and by 0.353 log10 unit/h during aerobic thermophilic fermentation. Furthermore, pasteurization at 70 degrees C for 30 min inactivated the parvovirus by 0.72 log10 unit/30 min. In all experiments the contribution of temperature to the total inactivation was determined separately and was found to be predominant at process temperatures above 54 degrees C. In conclusion, the most favorable treatment to render sludge hygienically safe from the virological point of view would be a thermal treatment (60 degrees C) to inactivate thermolabile viruses, followed by an anaerobic mesophilic digestion to eliminate thermostable viruses that are more sensitive to chemical and microbial inactivations.     

Inactivation of animal viruses during sewage sludge treatment

Using a previously developed filter adsorption technique, the inactivation of a human rotavirus, a coxsackievirus B5, and a bovine parvovirus was monitored during sludge treatment processes. During conventional anaerobic mesophilic digestion at 35 to 36 degrees C, only minor inactivation of all three viruses occurred. The k' values measured were 0.314 log10 unit/day for rotavirus, 0.475 log10 unit/day for coxsackievirus B5, and 0.944 log10 unit/day for parvovirus. However, anaerobic thermophilic digestion at 54 to 56 degrees C led to rapid inactivation of rotavirus (k' greater than 8.5 log10 units/h) and of coxsackievirus B5 (k' greater than 0.93 log10 unit/min). Similarly, aerobic thermophilic fermentation at 60 to 61 degrees C rapidly inactivated rotavirus (k' = 0.75 log10 unit/min) and coxsackievirus B5 (k' greater than 1.67 log10 units/min). Infectivity of parvovirus, however, was only reduced by 0.213 log10 unit/h during anaerobic thermophilic digestion and by 0.353 log10 unit/h during aerobic thermophilic fermentation. Furthermore, pasteurization at 70 degrees C for 30 min inactivated the parvovirus by 0.72 log10 unit/30 min. In all experiments the contribution of temperature to the total inactivation was determined separately and was found to be predominant at process temperatures above 54 degrees C. In conclusion, the most favorable treatment to render sludge hygienically safe from the virological point of view would be a thermal treatment (60 degrees C) to inactivate thermolabile viruses, followed by an anaerobic mesophilic digestion to eliminate thermostable viruses that are more sensitive to chemical and microbial inactivations.     

Fungal community assembly during a high-temperature composting under different pasteurization regimes used to elaborate the Agaricus bisporus substrate

Agaricus bisporus cultivation is based on a selective substrate prepared by a meticulous composting process where thermophilic and/or thermotolerant fungi might play an important role in straw biomass depolymerization. Since fungi have physiological limitations to survive and grow in high-temperature environments, we set out different pasteurization regimes (57 °C/6 h, 60 °C/2 h, and 68 °C/2 h) to evaluate the impact on the fungal community assembly. The fungal community profile generated by high-throughput sequencing showed shifts in community diversity and composition under different pasteurization regimes. Most of the recovered sequences belong to the Ascomycota phylum. Among 73 species detected, Mycothermus thermophilus, Talaromyces thermophilus, and Thermomyces lanuginosus were the most abundant. In the current study, we outlined that pasteurization regimes can reshape the fungal community in compost which can potentially impact the A. bisporus development.     

Combined effects of spray‐drying conditions and postdrying storage time and temperature on Salmonella choleraesuis and Salmonella typhimurium survival when inoculated in liquid porcine plasma

The objective of this study was to determine the effectiveness of the spray‐drying process on the inactivation of Salmonella choleraesuis and Salmonella typhimurium spiked in liquid porcine plasma and to test the additive effect of immediate postdrying storage. Commercial spray‐dried porcine plasma was sterilized by irradiation and then reconstituted (1:9) with sterile water. Aliquots of reconstituted plasma were inoculated with either S. choleraesuis or S. typhimurium, subjected to spray‐drying at an inlet temperature of 200°C and an outlet temperature of either 71 or 80°C, and each spray‐drying temperature combinations were subjected to either 0, 30 or 60 s of residence time (RT) as a simulation of residence time typical of commercial dryers. Spray‐dried samples were stored at either 4·0 ± 3·0°C or 23·0 ± 0·3°C for 15 days. Bacterial counts of each Salmonella spp., were completed for all samples. For both Salmonella spp., spray‐drying at both outlet temperatures reduced bacterial counts about 3 logs at RT 0 s, while there was about a 5·5 log reduction at RT 60 s. Storage of all dried samples at either 4·0 ± 3·0°C or 23·0 ± 0·3°C for 15 days eliminate all detectable bacterial counts of both Salmonella spp.

Significance and Impact of the Study

Safety of raw materials from animal origin like spray‐dried porcine plasma (SDPP) may be a concern for the swine industry. Spray‐drying process and postdrying storage are good inactivation steps to reduce the bacterial load of Salmonella choleraesuis and Salmonella typhimurium. For both Salmonella spp., spray‐drying at 71°C or 80°C outlet temperatures reduced bacterial counts about 3 log at residence time (RT) 0 s, while there was about a 5.5 log reduction at RT 60 s. Storage of all dried samples at either 4.0 ± 3.0°C or 23.0 ± 0.3°C for 15 days was effective for eliminating detectable bacterial counts of both Salmonella spp.     

Performance and microbial community composition dynamics of aerobic granular sludge from sequencing batch bubble column reactors operated at 20 °C, 30 °C, and 35 °C

Two bubble column sequencing batch reactors fed with an artificial wastewater were operated at 20 °C, 30 °C, and 35 °C. In a first stage, stable granules were obtained at 20 °C, whereas fluffy structures were observed at 30 °C. Molecular analysis revealed high abundance of the operational taxonomic unit 208 (OTU 208) affiliating with filamentous bacteria Leptothrix spp. at 30 °C, an OTU much less abundant at 20 °C. The granular sludge obtained at 20 °C was used for the second stage during which one reactor was maintained at 20 °C and the second operated at 30 °C and 35 °C after prior gradual increase of temperature. Aerobic granular sludge with similar physical properties developed in both reactors but it had different nutrient elimination performances and microbial communities. At 20 °C, acetate was consumed during anaerobic feeding, and biological phosphorous removal was observed when Rhodocyclaceae-affiliating OTU 214 was present. At 30 °C and 35 °C, acetate was mainly consumed during aeration and phosphorous removal was insignificant. OTU 214 was almost absent but the Gammaproteobacteria-affiliating OTU 239 was more abundant than at 20 °C. Aerobic granular sludge at all temperatures contained abundantly the OTUs 224 and 289 affiliating with Sphingomonadaceae indicating that this bacterial family played an important role in maintaining stable granular structures.     

Performance of an UASB reactor treating synthetic wastewater at low-temperature using cold-adapted seed slurry

The present study is an attempt to investigate if a long-term acclimation of digester contents to low-temperatures would improve wastewater treatment at low-temperatures similar to mesophilic ranges. The feasibility of low-temperature (15 °C) anaerobic treatment of synthetic wastewater in an upflow anaerobic sludge blanket reactor was studied using inoculum from a cattle manure digester adapted to 15 °C. The effect of varying hydraulic retention time was studied by decreasing the retention time from 7 days to 1 day. Under a constant temperature of 15 °C with a hydraulic retention time of 1 day and a corresponding loading rate of 7.2 g-chemical oxygen demand (COD)/l/day, 90–95% removal efficiency was achieved. The methane production of 250 l/kg-COD removed at standard temperature pressure (STP) is a major highlight of the study complementing the high treatment efficiency achieved. Loading rates >5 g-COD/l/day was accompanied by increase in effluent volatile fatty acids (VFA) concentrations. Due to the presence of a high concentration of active granular sludge in the lower compartment of the reactor, 80% reduction of COD occurred within the granular bed of the reactor. Treatment of low strength wastewater for a short period showed 70–75% removal efficiencies with methane yield of 300 l/kg-COD removed. Specific methanogenic activity profiles of the anaerobic biomass revealed low-temperature (15 °C) optima, indicating selection of cold-active microorganisms during the acclimation process. The SMA assays also indicate the development of a putatively psychrophilic acetoclastic methanogenic community and biogas analysis showed 75% efficiency in energy recovery as methane.     

Enhancement of biochemical methane potential from excess sludge with low organic content by mild thermal pretreatment

Excess sludge with low organic content always led to the failure of anaerobic digestion for methane production. Recently, the mild thermal pretreatment, which is usually operated at temperatures below 120 °C, has drawn much attention due to less energy consumption and no chemical addition. In this study the effect of mild thermal pretreatment (50–120 °C) on the solubilization and methane potential of excess sludge with a low concentration of organic matters was investigated. Experimental results showed that the concentration of soluble organic matters increased gradually with temperature during the mild thermal pretreatment of excess sludge. Biochemical methane potential experiments demonstrated that the potential of methane production from excess sludge was greatly enhanced by mild thermal pretreatment, and under the conditions of pretreatment temperature 100 °C and digestion time 20 d the methane yield was as high as 142.6 ± 2.5 mL/g of volatile solids. Mechanism investigation on the enhancement of methane production from excess sludge exhibited that the consumptions of sludge protein and carbohydrate, the adenosine 5′-triphosphate content of anaerobic microorganisms, the activities of key enzymes related to anaerobic digestion, and the amount of methanogens were all improved by mild thermal pretreatment, in correspondence with the production of methane.     

Dry anaerobic ammonia–methane production from chicken manure

The effect of temperature on production of ammonia during dry anaerobic fermentation of chicken manure (CM), inoculated with thermophilic methanogenic sludge, was investigated in a batch condition for 8 days. Incubation temperature did not have a significant effect on the production of ammonia. Almost complete inhibition of production of methane occurred at 55 and 65°C while quite low yields of 8.45 and 6.34 ml g⁻¹ VS (volatile solids) were observed at 35 and 45°C due to a higher accumulation of ammonia. In order to improve the production of methane during dry anaerobic digestion of CM, stripping of ammonia was performed firstly on the CM previously fermented at 65°C for 8 days: the stripping for 1 day at 85°C and pH 10 removed 85.5% of ammonia. The first-batch fermentation of methane for 75 days was conducted next, using the ammonia-stripped CM inoculated with methanogenic sludge at different ratios, (CM: thermophilic sludge) of 1:2, 1:1, and 2:1 on volume per volume basis at both 35 and 55°C. Production of methane improved and was higher than that of the control (without stripping of ammonia) but the yield of 20.4 ml g⁻¹ VS was still low, so second stripping of ammonia was conducted, which resulted in 74.7% removal of ammonia. A great improvement in the production of methane of 103.5 ml g⁻¹ VS was achieved during the second batch for 55 days.     

Heat resistance of Clostridium sordellii spores

The thermal destruction kinetics of Clostridium sordellii spores was studied in this research. Decimal reduction times (D values) for C. sordellii ATCC 9714 spores ranged between 175.60 min for D₈₀ (the D value for spore suspensions treated at 80 °C) and 11.22 min for D₉₅. The thermal resistance (Z) and temperature coefficient (Q₁₀) values of spores were calculated to be as high as 12.59 °C and 6.23, respectively. At 95 °C, the relative thermal death rate and relative thermal death time of C. sordellii ATCC 9714 spores were found to be 0.0085/min and 118 min, respectively, indicating that the death rate of spores was 118 times lower at 95 °C than at 121.1 °C. Heat treatments at up to 85 °C for 120 min failed to cause a 100-fold destruction in spore populations of C. sordellii ATCC 9714. By contrast, spore counts were reduced by 2log₁₀ cycles within 73 min and 23 min at 90 °C and 95 °C, respectively. This is the first published report of thermal inactivation of C. sordellii spores; however, further studies are needed to confirm these results in real food samples.     

Physical Covering for Control of Escherichia coli O157:H7 and Salmonella spp. in Static and Windrow Composting Processes

This study investigated the effect of a 30-cm covering of finished compost (FC) on survival of Escherichia coli O157:H7 and Salmonella spp. in active static and windrow composting systems. Feedstocks inoculated with E. coli O157:H7 (7.41 log CFU/g) and Salmonella (6.46 log CFU/g) were placed in biosentry tubes (7.5-cm diameter, 30-cm height) at three locations: (i and ii) two opposing sides at the interface between the FC cover layer (where present) and the feedstock material (each positioned approximately 10 cm below the pile''s surface) and (iii) an internal location (top) (approximately 30 cm below the surface). On specific sampling days, surviving populations of inoculated E. coli O157:H7 and Salmonella, generic E. coli, and coliforms in compost samples were determined. Salmonella spp. were reduced significantly within 24 h in windrow piles and were below the detection limit after 3 and 7 days at internal locations of windrow and static piles containing FC covering, respectively. Likewise, E. coli O157:H7 was undetectable after 1 day in windrow piles covered with finished compost. Use of FC as a covering layer significantly increased the number of days that temperatures in the windrows remained ≥55°C at all locations and in static piles at internal locations. These time-temperature exposures resulted in rapid reduction of inoculated pathogens, and the rate of bacterial reduction was rapid in windrow piles. The sample location significantly influenced the survival of these pathogens at internal locations compared to that at interface locations of piles. Finished compost covering of compost piles aids in the reduction of pathogens during the composting process.     

Microbial sulfate reduction at low (8 °C) temperature using waste sludge as a carbon and seed source

Biological treatment of sulfate and metal-containing wastewater (such as acid mine drainage) is a viable option due to lower cost and better sludge quality compared to conventional chemical treatment. Although several substrates can be used as carbon source, a low-cost substrate is required for large scale applications. This study was conducted to investigate the suitability of waste sludge as a carbon and seed source for sulfate reduction at 8 °C in batch bioassays. Around 7 mmol of sulfate was reduced when the waste sludge mixture (WS) (6700 mg SS l^?1) from primary and secondary settling tank was supplemented as a carbon and seed source. However, only 1.6 mmol of sulfate was reduced with anaerobic digester effluent (ADS) (5300 mg SS l^?1). The produced H₂S from 1 g VSS l^?1 WS and ADS oxidation can theoretically precipitate around 90 and 35 mg Fe²⁺, respectively. Both WS and ADS oxidized ethanol to acetate at similar rates. It appears that WS is a good candidate for carbon and start-up seed source of sulfate reduction at 8 °C, whereas sulfidogenic acetate oxidation was the limiting step. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA genes showed that both sludge sources contain Desulfomicrobium apsheronum strain.     

Viral clearance during the manufacture of urokinase from human urine

The purpose of the present study was to evaluate the efficacies and mechanisms of the PAB (para-amino benzamidine) affinity column chromatography, virus filtration, pasteurization (60°C heat treatment for 10 h), and lyophilization steps employed in the manufacture of urokinase from human urine with regard to the removal and/or inactivation of human immunodeficiency virus (HIV), bovine viral diarrhoea virus (BVDV), bovine herpes virus (BHV), and murine encephalomyocarditis virus (EMCV). Samples from relevant stages of the production process were spiked with each virus and subjected to scale-down processes mimicking the manufacture of urokinase. Samples were collected at each step, immediately titrated using a 50% tissue culture infectious dose (TCID₅₀), and the virus reduction factors evaluated. PAB chromatography was found to be an effective step for removing BVDV, BHV, and EMCV with log reduction factors of 2.79, 6.50, and 5.96, respectively. HIV, BVDV, BHV, and EMCV were completely removed during the Viresolve NFP filtration step with log reduction factors of ≥6.06, ≥4.60, ≥5.44, and ≥6.87, respectively. Pasteurization was also found to be a robust and effective step in inactivating all the viruses tested, since there were no residual viruses detected after the pasteurization process. The log reduction factors achieved by pasteurization were ≥5.73 for HIV, ≥3.86 for BVDV, ≥6.75 for BHV, and ≥5.92 for EMCV. Lyophilization showed significant efficacy for inactivating BVDV, BHV, and EMCV with log reduction factors of 2.69, 1.37, and 4.70, respectively. These results indicate that the production process for urokinase exhibited a sufficient viral reducing capacity to achieve a high margin of virus safety.     

Biochemical characterization of a novel thermostable xyloglucanase from an alkalothermophilic Thermomonospora sp.

Xyloglucanase from an extracellular culture filtrate of alkalothermophilic Thermomonospora sp. was purified to homogeneity with a molecular weight of 144 kDa as determined by SDS-PAGE and exhibited specificity towards xyloglucan with apparent K _m of 1.67 mg/ml. The enzyme was active at a broad range of pH (5–8) and temperatures (40–80°C). The optimum pH and temperature were 7 and 70°C, respectively. The enzyme retained 100% activity at 50°C for 60 h with half-lives of 14 h, 6 h and 7 min at 60, 70 and 80°C, respectively. The kinetics of thermal denaturation revealed that the inactivation at 80°C is due to unfolding of the enzyme as evidenced by the distinct red shift in the wavelength maximum of the fluorescence profile. Xyloglucanase activity was positively modulated in the presence of Zn²⁺, K⁺, cysteine, β-mercaptoethanol and polyols. Thermostability was enhanced in the presence of additives (polyols and glycine) at 80°C. A hydrolysis of 55% for galactoxyloglucan (GXG) from tamarind kernel powder (TKP) was obtained in 12 h at 60°C and 6 h at 70°C using thermostable xyloglucanases, favouring a reduction in process time and enzyme dosage. The enzyme was stable in the presence of commercial detergents (Ariel), indicating its potential as an additive to laundry detergents.     

Removal and inactivation of human immunodeficiency virus (HIV-1) by cold ethanol fractionation and pasteurization during the manufacturing of albumin and immunoglobulins from human plasma

Viral safety is a prerequisite for manufacturing clinical albumin and immunoglobulins from human plasma pools. This study was designed to evaluate the efficacy of cold ethanol fractionation and pasteurization (60°C heat treatment for 10 h) for the removal inactivation of human immunodeficiency virus type 1 (HIV-1) during the manufacturing of albumin and immunoglobulins. Samples from the relevant stages of the production process were spiked with HIV-1, and the amount of virus in each fraction was quantified by the 50% tissue culture infectious dose (TCID₅₀). Both fraction IV fractionation and pasteurization steps during albumin processing were robust and effective in inactivating HIV-1, titers of which were reduced from an initial 8.5 log₁₀ TCID₅₀ to undetectable levels. The log reduction factors achieved were ≥4.5 and ≥6.5, respectively. In addition, fraction III fractionation and pasteurization during immunoglobulins processing were robust and effective in eliminating HIV-1. HIV-1 titers were reduced from an initial 7.3 log₁₀ TCID₅₀ to undetectable levels. The log reduction factors achieved in this case were ≥4.9 and ≥5.3, respectively. These results indicate that the process investigated for the production of albumin and immunoglobulins have sufficient HIV-1 reducing capacity to achieve a high margin of safety.     

Degradation of polyesteramides during composting under standard and isothermal conditions

Polyesteramides based on ɛ-caprolactam and ɛ-caprolactone differing in the content of ester-amide structural units were subjected to biodegradation — composting in a big compost pile under controlled conditions (controlled composting) and in small composters at a steady temperature of 60 °C (isothermal composting). Both types of composting resulted in degradation of the polyesteramides depending on copolymer composition, isothermal composting being more robust. The contribution of abiotic hydrolysis to the degradation of polyesteramides was studied at 60 °C in buffer solutions with pH 5.4, 7.4 and 8.4. The prevailing effect of abiotic hydrolysis over biological one was shown at 60 °C. Ester bonds in polyestramide chains were preferentially cleaved; therefore, the scope of degradation increased with the content of ester units in the copolymer.     

Cold ethanol fractionation and heat inactivation of hepatitis a virus during manufacture of albumin from human plasma

The purpose of the present study was to examine the efficacy and mechanism of fraction IV cold ethanol fractionation and pasteurization (60°C heat treatment for 10h), involved in the manufacture of albumin from human plasma, in the removal and/or inactivation of the hepatitis A virus (HAV). Samples from the relevant stages of the production process were spiked with HAV and the amount of virus in each fraction then quantified using a 50% tissue culture infectious dose (TCID₅₀). HAV was effectively partitioned from albumin during the fraction IV cold ethanol fractionation with a log reduction factor of 3.43. Pasteurization was also found to be a robust and effective step in inactivating HAV, where the titers were reduced from an initial titer of 7.60 log TCID₅₀ to undetectable levels within 5 h of treatment. The log reduction factor achieved during pasteurization was≽4.76. Therefore, the current results indicate that the production process for albumin has sufficient HAV reducing capacity to achieve a high margin of virus safety.     

The modelling of combined strategies to achieve thermophilic composting of sludge in cold region

Low ambient temperature presents a significant technical challenge for efficient operation of the composting facility located in cold region. In this study, mathematical model was used as a tool to develop the operational strategy to accomplish thermophilic composting of sewage sludge in the cold-climate environment. The correlations between composting temperature, water volatilization, heat loss rate, organics degradation and ambient temperature, feedstock temperature, sludge moisture and aeration rate were predicted and evaluated by using the numerical simulation method. The feasibility of optimizing air supply, adjusting feedstock moisture and elevating starting temperature in the low temperature surroundings was investigated. The results obtained from both mathematical modelling and pilot-scale composting experiments demonstrated that the combined strategies of the three approaches could preliminarily achieve material drying, pathogen inactivation and organics stabilization within 20 days at the ambient temperature as low as −24 °C. However, it seems difficult for anyone of these approaches to meet the requirement of thermophilic composting, independently.     

Changes in physical,chemical and microbial parameters during the composting of municipal sewage sludge

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.