Background: Disposal of vegetable waste in landfills and illegal sites leads to emission of greenhouse gases and leachate production, thereby imposing major environmental issues. As an alternative, this waste can be successfully recycled for its high nutrient content using composting process.Results: Five trials were made with the ratio of 6: 3: 1 of trial 1 (50 kg), trial 2 (70 kg), trial 3 (90 kg), trial 4 (120 kg) and trial 5 (150 kg) by adding 10 kg of dry leaves in each of the trials as bulking agent. Due to active microbial population and high biodegradable organic matter in vegetable waste, early thermophilic phase was observed within 18–24 h of the composting process in all of the trials with a maximum of 61.4oC in trial 3. Total mesophilic heterotrophs were observed in the range of 7.19 1011 CFU g-1 and gradually reduced to 2.65 9 106 CFU g-1 at the end of 20 days, which was considered due to prolonged thermophilic phase maintained in trial 3. An average of 54–56oC temperature was maintained for 7 days in trial 3, with spore-forming population in the order of 3.829 109 CFU g-1 contributing to higher organic destruction. The populations of fungus, actinomycetes and streptomycetes were observed to reduce during thermophilic phase and remained in the order of 2.859 104, 3.89 106 and 4.1 9 105 CFU g-1, respectively, at the end of 20 days. CO2 evolution and OUR were in the order of 0.89 and 0.32 mg g-1 VS d-1, respectively, in trial 3 denoting maximum degradation of organic matter and stabilization of compost. Indicator organisms were found well with the standard limits due to elevated temperature.Conclusions: Combinations of waste materials played a major role in favoring microbial succession. Temperature in the compost system had major effect on the survival of the microbial populations. Elevated temperatures favored higher degradation of organic matter, thereby stabilizing the compost within proposed time of composting and also destructing the indicator pathogens.

Purpose: The present work aims to isolate and identify bacterial community from the Rotary drum compost of green waste such as the water hyacinth. Compost quality was also investigated with the physicochemical parameters and the heavy metal analysis.Methods: For Rotary drum composting, a waste mixture of 150 kg with water hyacinth, cow dung and sawdust were prepared in the proportion of 6: 3: 1, respectively. The physicochemical parameters such as pH, temperature, volatile solids and the electrical conductivity were analyzed to detect the compost quality. Pb, Ni, Zn, and Cd were investigated for total heavy metals, toxicity characteristic leaching procedure (TCLP), diethylenetriamine pentaacetic acid (DTPA) and water solubility tests.Consistent and active bacterial community were isolated from the Rotary drum compost of water hyacinth. Culture dependent and culture-independent techniques were approached for the isolation process.Results: Twelve bacteria were isolated and identified by 16S rDNA sequencing and phylogenetic analysis; they majorly belonged to the Bacillus and Enterobacter family.The analysis of temperature, pH, EC, VS and heavy metals depicted the good quality of compost. Heavy metals concentration was in Pb[Ni [Zn [Cd; however, for Pb, Cd and Ni water solubility remained non-detectable, DTPA concentration for Pb and Cd was also found to be nondetectable.Conclusions: The microbes in water hyacinth compost are metabolically active degrading the organic matter, surviving in the heavy metal-loaded compost environment. Thus, green waste (water hyacinth) can be utilized to isolate bacterial species in anticipation of their application in heavy metal removal in liquid and solid waste sources for micro-bioremediation.

Background: Composting is one of the sustainable practices to convert sewage sludge into useful agricultural product because it is rich in organic matter, micro- and macronutrients, which is essential for plants growth and soil fauna to live. Therefore, the present study was to recycle the sewage sludge by Rotary drum composter. Five sets of experiments (C/N 15, 20, 25, 30 including control) were carried out in the reactor, where sewage sludge was coupled with sawdust and cattle manure to attain the optimal feedstock. The process was monitored with respect to physico-chemical characteristics and stability parameters during 20 days of composting period. In addition, the kinetic parameterskm and rm have been evaluated in the present work.ResultsHigher reductions in CO2 evolution and oxygen uptake rate (OUR) observed in C/N 30 showed the stability, resulting in the total biodegradable ingredients to be stabilized. Similarly, higher percentage reduction in carbon-nitrogen ratio was observed in C/N 30 followed by C/N 20, C/N 25, C/N 15 and control experiments, respectively, indicates maximum degradation was achieved; as it corroborate higher temperature regime occurred in C/N 30.The composting parameters such as moisture content, volatile solids, CO2 evolution, OUR and C/N ratio were reduced significantly (p<0.05). The kinetic model used illustrated the comparable variations in Michaelis constant (km) and maximum rate constant (rm) under varying proportions of the initial feedstock. The overall assessment of kinetic data for C/N 30 experiment showed enhancement of degradation during the composting process.ConclusionsThe results suggested that composting of sewage sludge with optimal proportion of cattle manure and saw dust, especially in C/N 30, can produce stable compost within 20 days of composting.

Background: Water hyacinth (Eichhorniacrassipes) is one of the most uncompromising weeds in the whole world. Its adverse effects due to fast growth rate are main physical interference with fishing and navigation. Water hyacinth also causes eutrophication due to the large release of organic nutrients after its degradation, consequentially deterioration of water quality and also adversely affecting aquatic flora and fauna. Therefore, composting is one of the best methods for control and utilization of water hyacinth. Water hyacinth being the plant material is rich in cellulose, hemicellulose, and lignin content which hinders the rate of degradation during composting. The raw materials including water hyacinth along with sawdust and cattle manure in five different proportions trial 1 (10: 0: 0), trial 2 (8: 1: 1), trial 3 (7: 2: 1), trial 4 (6: 3: 1), and trial 5 (5: 4: 1) were composted using Rotary drum composter.Results: Final product of water hyacinth composting was flourishing of nutrients such as nitrogen, phosphorus, sodium, potassium, calcium, and magnesium. The lignin reduction in all the five trials was obtained between 10 and 40%. The reduction in cellulose was observed ranging from 4 to 55% in different trials. Similar as cellulose and lignin, hemicellulose was also reduced about 11-46% in all five trials during the process.Conclusion: The maximum reduction inorganic matter, lignin, cellulose and hemicellulose was observed in trial 4; whereas, the nutrient contents (nitrogen, phosphorus, Na, K, Ca, and Mg) were increased significantly during the process. On analyzing the FTIR results, trial 4 showed that aliphatic and polysaccharides have easily degraded and aromatic compounds have increased with composting time in trial 4.

Vegetable waste usually contains high levels of organic matter, moisture and nutrients that make the waste unsuitable for disposal in municipal landfills. Composting of vegetable waste is in practice by many urban local bodies, and therefore, it was composted along with cow dung and sawdust in a 550-L batch scale Rotary drum composter. Four different trials of varying waste combinations of vegetable waste, cow dung and sawdust, i.e., trial 1 (5:4:1), trial 2 (6:2:1), trial 3 (7:2:1) and trial 4 (8:1:1) were composted by adding 10 kg of dry leaves as bulking agent with a total mass of 100 kg. With proper combinations of organic waste mix, a maximum temperature of 66.5oC was observed in trial 1 and 61.4 °C in trial 2, when compared to other two trials with prolonged thermophilic period. Due to such elevated temperature, higher degradation was observed in trials 1 and 2 with inactivation of pathogens to considerable amounts. Furthermore, final compost had total nitrogen of 2.31 and 3.01 %, total phosphorous of 4.30 and 3.27 % and final carbon-to-nitrogen ratio of 15 and 12, in trials 1 and 2, respectively. Carbon dioxide evolution and oxygen uptake rate of compost samples was analyzed for its stability and was observed to reduce completely at the end of 20 days with lower emission rates.

This study is aimed to investigate the effect of a Hybrid Hot air-Microwave-Rotary drum (HMRD) dryer on the thermal properties, quality, and nutritional characteristics of green pea under different operational conditions. The experiments were conducted under different air temperatures (40, 55, and 70 ° C), microwave power (90, 270, 450, and 630 W), and drum rotation speeds (5, 10, and 15 rpm). The thermal properties (e. g. drying time, effective moisture diffusion coefficient, activation energy, and specific energy consumption), quality features (color, shrinkage, and rehydration ratio), and nutritional properties (antioxidant activity and total phenol content) were determined. The results indicated that by increasing the microwave power, air temperature, and drum rotation speed, the drying time will decline. The highest diffusion coefficient and energy consumption were determined as 5. 04×10-11 m2/s and 109. 91 MJ/kg, respectively. The lowest changes in color, shrinkage and rehydration were calculated as 41. 34, 24. 08%, and 1. 57. The highest total phenol (14. 02 mg GAE/g d. w) and antioxidant (85. 86%) were obtained. Thus the newly designed dryer can be employed for drying the granular products and lead to satisfactory results.