Rotary Drum Composter Research Articles

Study on effects of temperature, moisture and pH in degradation and degradation kinetics of aldrin, endosulfan, lindane pesticides during full-scale continuous rotary drum composting

Study focused on effects of temperature, moisture and pH on degradation and degradation kinetics of aldrin, endosulfan (α), endosulfan (β) and lindane during vegetable waste composting using full-scale continuous rotary drum composter (FSCRDC). Extraction, concentration and quantification of pesticides were made from waste material at different stages by ultra-sonification, silica gel column and GC–MS analysis. Removal efficiency of aldrin, endosulfan α, endosulfan β and lindane was found 85.67%, 84.95%, 83.20% and 81.36% respectively due to optimum temperature, moisture, pH and enhanced microbial activity. Maximum temperature in inlet zone was found 60–65°C which is most suitable for complex microbial population. After feeding and turning in inlet zone, temperature reduced to 38°C from 60 to 65°C and regained it within 7–8h, and pH reduced to 5.3±0.2 from 7.5±0.3 in 4h and regained it in 10h. Heterotrophic bacteria Bacillus sp., Pseudomonas sp. and Lactobacillus sp. also decreased from 4.4×103 to 7.80×102CFUg−1 in 2h due to gradual variation in temperature and pH. No significant temperature change was found in middle and outlet zones during feeding and turning. Degradation of pesticides was observed as first order kinetics and half-life of aldrin, endosulfan α, endosulfan β and lindane was reduced to 25.54, 18.43, 18.43 and 27.43d from 1095, 60, 270 and 160d respectively. Thus, the observations in contrast of removal and degradation kinetics of organochlorine pesticides residues in vegetable waste though full-scale rotary drum composting proved it the best suited technique.

Influences of natural zeolite on speciation of heavy metals during rotary drum composting of green waste

The presence of heavy metals in water hyacinth compost is the main limiting factor for its land application. Water hyacinth can accumulate heavy metals in its tissues. Application of natural zeolites (clinoptilolite) during water hyacinth composting may be helpful to immobilise heavy metals. The present study was carried out on the speciation of heavy metals (Zn, Cu, Mn, Fe, Pb, Ni, Cd and Cr) during rotary drum composting of water hyacinth mixed with cattle manure, sawdust and natural zeolite. The Tessier sequential extraction method was used for heavy metal speciation determination. The water hyacinth, cattle manure and sawdust at a ratio of 6:3:1 ratio was mixed with 5, 10 and 15% natural zeolite by weight. Influences of physicochemical parameters such as temperature, pH and organic matter degradation on speciation of heavy metals were studied during the process. A rotary drum composter has been shown to be highly efficient for organic matter degradation. The most bioavailable fractions (exchangeable and carbonate fractions) were reduced significantly due to the combined effects of zeolite addition and metal complexing with stabilised organic matter as a result of the high degradation of organic matter in a rotary drum. Ni, Pb and Cd were not found in the reducible and oxidisable fractions. Overall, the addition of an optimum quantity of natural zeolite significantly reduced the bioavailability fractions of heavy metals during rotary drum composting of the water hyacinth.

Effect of carbide sludge (lime) on bioavailability and leachability of heavy metals during rotary drum composting of water hyacinth

The bioavailability and leachability of heavy metals play a major role in the toxicity of heavy metals in the compost applied for soil conditioning. A rotary drum composter was used for the study of heavy metal bioavailability and leachability during water hyacinth composting with a mixture of cattle manure, sawdust and lime. Lime was added in 1, 2 and 3% to the mixture of water hyacinth, cattle manure and sawdust at a ratio of 6:3:1 respectively. Influences of physico-chemical parameters on heavy metal bioavailability and leachability were studied during the process. The bioavailability of heavy metals solubility and diethylene triamine penta-acetic acid extractability was examined. The toxicity characteristics leaching procedure (TCLP) test was performed for assessing the hazardous properties of compost. The nutrients and the total concentration of heavy metals were increased during the composting process. The lime was very effective in reducing water solubility, plant availability and leachability of the selected heavy metals (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr) during the process. The addition of lime provided a buffer against the decrease in pH and a sufficient amount of Ca that would improve the metabolic activity during composting. The addition of an excess amount of lime slowed the metabolic activity of the microbes due to its high alkalinity. The TCLP test confirms that the heavy metals concentrations in the control and in the lime-amended compost were below the threshold limits.

Diversity of bacterial isolates during full scale rotary drum composting

Bacterial diversity of full scale rotary drum composter from biodegradable organic waste samples were analyzed through two different approaches, i.e., Culture dependent and independent techniques. Culture-dependent enumerations for indigenous population of bacterial isolates mainly total heterotrophic bacteria (Bacillus species, Pseudomonas species and Enterobacter species), Fecal Coliforms, Fecal Streptococci, Escherichia coli, Salmonella species and Shigella species showed reduction during the composting period. On the other hand, Culture-independent method using PCR amplification of specific 16S rRNA sequences identified the presence of Acinetobacter species, Actinobacteria species, Bacillus species, Clostridium species, Hydrogenophaga species, Butyrivibrio species, Pedobacter species, Empedobactor species and Flavobacterium species by sequences clustering in the phylogenetic tree. Furthermore, correlating physico-chemical analysis of samples with bacterial diversity revealed the bacterial communities have undergone changes, possibly linked to the variations in temperature and availability of new metabolic substrates while decomposing organics at different stages of composting.

Assessment of bioavailability and leachability of heavy metals during rotary drum composting of green waste (Water hyacinth)

Studies were carried out on bioavailability and leachability of heavy metals (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr) during rotary drum composting of water hyacinth (Eichhornia crassipes) for 20 days. This study investigates the influence of physic-chemical parameters such as pH, temperature and organic matter content on distribution of heavy metal bioavailability and leachability during water hyacinth composting. The bioavailability was investigated in the form of water soluble and diethylenetriamine penta-acetic acid (DTPA) extractable. Results show that during composting, the total metal concentration was increased. Water soluble Ni, Cd and Pb and DTPA extractable Cd and Pb were not detected but all metal concentration were observed by TCLP test during the composting process. Leachability of Cd was very low among all the eight metals analyzed. The optimum proportion of cattle manure can enhance organic matter degradation and humification process; consequently it reduced the toxicity of metals during rotary drum composting.

Composting of Water Hyacinth using a Pilot Scale Rotary Drum Composter

Composting of water hyacinth, mixed with cattle manure, rice husk and sawdust in four different proportions, was performed in a pilot scale rotary drum composter. The physico-chemical characteristics, i.e., temperature, moisture content, pH, electrical conductiv- ity, total organic matter (OM), nitrogen dynamics and nutrients were evaluated during the 20 days composting process. The stabilities of the composts were also investigated with respirometric analysis, i.e., CO2 evolution rates and oxygen uptake rate (OUR). Among all trials, trial 1 (6 water hyacinth, 3 cattle manure, 1 rice husk) indicated the best composting mix, as shown by the highest temperature profile and OM loss, and lowest CO2 evolution rate and OUR.

Maturity Assessment of Rotary Drum and Windrow Composts In Terms of Germination Index and Enzymatic Activities

Better efficiency of composting process for domestic solid waste was calculated after monitoring two kinds of composting systems viz., Rotary drum composting and windrow composting system. Physico-chemical parameters, enzymatic activity and germination index test were analyzed. A statistical correlation was adopted between germination index values and enzymatic activity. The correlated values were relatively higher in case of rotary drum composting system as compared to windrow pile, having highly significant (P<0.01). Judging from the study results, drum composting system was relatively mature with higher degradation rate, enzymatic activity and germination index, producing the resultant biodegradable product as a manure of better quality in lesser period of drum composting in comparison to windrow composting system.

High rate composting of herbal pharmaceutical industry solid waste

High rate composting studies of hard to degrade herbal wastes were conducted in a 3.5 m(3) capacity rotary drum composter. Studies were spread out in four trials: In trial 1 and 2, one and two turns per day rotation was observed, respectively, by mixing of herbal industry waste with cattle (buffalo) manure at a ratio of 3:1 on wet weight basis. In trial 3 inocula was added in raw waste to enhance the degradation and in trial 4 composting of a mixture of vegetable market waste and herbal waste was conducted at one turn per day. Results demonstrated that the operation of the rotary drum at one turn a day (trial 1) could provide the most conducive composting conditions and co-composting (trial 4) gave better quality compost in terms of temperature, moisture, nitrogen, and Solvita maturity index. In addition a FT-IR study also revealed that trial 1 and trial 4 gave quality compost in terms of stability and maturity due to the presence of more intense peaks in the aromatic region and less intense peaks were found in the aliphatic region compared with trial 2 and trial 3.

Drum composting of municipal solid waste

The high initial C/N ratio (>30) found in Indian municipal solid waste (MSW) leads to more time required for composting (>3 months), with poor-quality compost production. Therefore, the effects of MSW amended with cattle manure (trial 1) and tree leaves (trial 2) were compared with unamended MSW (control) in a rotary drum composter. The initial C/N ratios of trial 1 and trial 2 were kept at 22, as compared to 32 for the MSW control sample. It was observed that trial 1 produced high-quality and stable compost within 20 days. It showed higher final total nitrogen (2.2%), final total phosphorus (3.2 g/kg) and low electrical conductivity (2.7 dS/m). At the end of 20 days, higher degradation caused lower final oxygen uptake rate (OUR) (1.8 mg/g volatile solids (VS)/day), final CO2 evolution (1.0 mg/g VS/day) and final C/N ratio (7.8). Trial 2 produced good-quality and stable compost resulting in 1.9% of total nitrogen, 2.7% of total phosphorus and low OUR (2.0 mg/g VS/day), CO2 evolution (1.5 mg/g VS/day) and C/N ratio (10.1) after 20 days of composting. However, the control sample with an initial C/N ratio of 32 showed higher OUR (3.6 mg/g VS/day) and CO2 evolution (2.6 mg/g VS/day) comprising a lower concentration of total nitrogen (1.6%) and total phosphorus (2.3 g/kg), which indicated an unstable and low-quality product as compared to trials 1 and 2. Therefore, results showed that the characteristics of MSW amended with cattle manure and tree leaves significantly influence the compost quality and process dynamics in a rotary drum composter.

Microbial diversity during Rotary Drum and Windrow Pile composting

This study investigates the prevailing microbial communities during the composting of vegetable waste, cattle manure and saw dust, in a household (250 l) batch scale Rotary Drum composter and Windrow Pile. Physico-chemical parameters were analyzed to study the organic matter transformations. Total organic matter reduced from 63.8% to 36.2% in rotary drum and 39.6% in windrow pile composting. The C/N ratio decreased from 26.52 to 8.89 and 14.33 in rotary drum and windrow pile composting. The indigenous population of total heterotrophic bacteria decreased in rotary drum and windrow pile composting after 20 days. However, total fungal load initially increased within initial 4 days, then subsequently reduced in final composts. The average number of fecal coliforms and fecal Streptococci showed decrement with time, in both composting systems. Escherichia coli and Salmonella species number deduced during the study. Composting cycle started with Gram positive rods but ended up with the dominance of Gram negative bacilli shaped bacteria. Transformation of organic compounds during the biodegradation of organic waste, difference in the utilization of nutrients (organic matter) by the different group of microbes and high temperature could be cited as a possible reason of the above changes. Scanning electron microscopy has been used to obtain the surface structures of the cultured mycoflora. Results of the study revealed that higher diversity of microbes prevailed in rotary drum as compared to windrow pile, yielding more stable and pathogenic free compost in lesser period of composting.

Rotary drum composting of vegetable waste and tree leaves

High rate composting studies on institutional waste, i.e. vegetable wastes, tree leaves, etc., were conducted on a demonstration-scale (3.5 m 3) rotary drum composter by evaluating changes in some physico-chemical and biological parameters. During composting, higher temperature (60–70 °C) at inlet zone and (50–60 °C) at middle zone were achieved which resulted in high degradation in the drum. As a result, all parameters including TOC, C/ N ratio, CO 2 evolution and coliforms were decreased significantly within few days of composting. Within a week period, quality compost with total nitrogen (2.6%) and final total phosphorus (6 g/kg) was achieved; but relatively higher final values of fecal coliforms and CO 2 evolution, suggested further maturation. Thus, two conventional composting methods namely windrow (M1) and vermicomposting (M2) tried for maturation of primary stabilized compost. By examining these methods, it was suggested that M2 was found suitable in delivering fine grained, better quality matured compost within 20 days of maturation period.

Maturation of primary stabilized compost from rotary drum composter

Information on maturation process of primary stabilized compost from rotary drum composter for the mixed organic wastes is rather limited. Thus, seven different maturation methods namely windrow ( L/ W = 6, T1), windrow ( L/ W = 2.5, T2), vermicomposting ( Eisenia foetida) (T3), packing in jute bags (T4), pile with longitudinal pipe for aeration ( L/ W = 6) (T5), pile with longitudinal pipe for aeration ( L/ W = 2.5, T6) and pile with lateral pipe for aeration ( L/ W = 6, T7) have been tried to optimize the maturation period. In addition, seasonal variation (ambient temperature and relative humidity) effects on maturation were also taken into account. The quality of matured compost was assessed by analyzing moisture content, pH, organic matter and stability parameters such as CO 2 evolution rate and oxygen uptake rate (OUR). By examining these parameters, it is suggested that methods T3 (vermicomposting) and T1 (windrow, L/ W = 6) were found suitable in delivering better quality matured compost within 20 days. A new relationship has been worked out between easily measurable parameters such as moisture content, pH, organic matter and the principal maturation parameter i.e., CO 2 evolution rate and found to be satisfactorily applicable to check compost stability and maturity.

Effects of C/N ratio on mixed organic waste composting in a rotary drum composter

Effects of Carbon to Nitrogen (C/N) ratio on the rotary drum composting of organic waste were examined by measuring changes in various parameters. It was observed that time courses of four C/N ratios: 16, 22, 30 and 38 were different. Initial C/N ratio 22 produced high-quality compost (total nitrogen-2.1%, total phosphorus-4.3 g/kg) within 20 days. While in case of C/N 16, compost yields 1.8% total nitrogen and 6.4 g/kg total phosphorus but, it showed higher NH+4-N and moisture content. C/N 30 and 38 showed lower amounts of total nitrogen and phosphorus and higher final coliform bacteria. Therefore, mixed organic waste composting in rotary drum at an initial C/N ratio of 22 can produce quality compost.

Effects of turning frequency on compost stability and some chemical characteristics in a rotary drum composter

Effect of turning frequency on quality, namely some chemical characteristics (temperature, moisture content, pH, electrical conductivity, total organic matter, nitrogen dynamics, phosphorus and trace elements) and stability of compost (biochemical oxygen demand, chemical oxygen demand, rate of oxygen consumption and carbon dioxide evolution) in a rotary drum were studied. Composting was stimulated by three turns of rotary drum at different time intervals i.e. at the gap of 6h (Run A), 12h (Run B), 18h (Run C) and 24h (Run D) for 15d. It was observed that Run D (24h turning frequency) caused longer thermophilic phase (4d) with a higher rise at temperature 58°C; consequently, peak of maximum temperature was shifted along with the increase of turning frequency. Around 23% of available carbon in Run D was utilized by micro-organisms and contained lower final electrical conductivity (1.32dSm−1) possibly causing lesser phytotoxicity effects on the growth of plants. The percentage increase in total nitrogen and total phosphorus (organic and inorganic) in Run D was found to be 45% and 37% as compared to 7% and 17%, 6% and 32% and 18% and 30% in Run A, B, and C, respectively, indicating higher mineralization. The final values of respiration rates (CO2 evolution and oxygen uptake rate) for Run D was found to be the lowest, nevertheless, other runs also provided relatively stable compost.

Stability evaluation of compost by respiration techniques in a rotary drum composter

Stability of compost using respiration techniques is evaluated for four C/N ratio waste combinations (C/N 16, C/N 22, C/N 30 and C/N 38) of grass cutting, mix vegetable waste, cattle manure, food waste and sawdust in a rotary drum composter. CO 2 evolution, oxygen uptake rate (OUR) was observed to asses the stability of compost. The CO 2 evolution rates for C/N ratio 16, 22, 30 and 38 decreased from initial values of 7.88, 7.24, 7.01 and 7.89 mg/g VS/day to 0.76, 0.84, 1.24 and 2.37 mg/g VS/day, respectively, strongly reflecting the viability of rotary drum for various types of organic wastes waste with varying C/N ratios. On analyzing the results by ANOVA, the decrease in CO 2 evolution varied significantly between the days ( P < 0.0001) and treatments (C/N ratios) ( P = 0.0013). On the other hand, ANOVA signify the variances between the soda lime and conductivity methods for CO 2 evolution are almost equal with P value greater than 0.001. Hence, it proves that conductivity method is reliable and authentic for evolution of CO 2. Oxygen uptake rate (OUR) dropped up to 0.808 mg/g VS/day for C/N 22, and 3.438, 3.106 and 3.98 mg/g VS/day for C/N 16, 30 and 38, respectively, after the 20 days of composting in the rotary drum. It was found out that compost of initial C/N 22 is considered as very mature with a Solvita ® maturity index (based on OUR) of 8. Therefore, it can be suggested that that rotary drum composting of mixed organic waste at initial C/N ratio of 22 can produce more stable compost within 20 days of composting. While, C/N 16, 30 and 38 has a Solvita ® maturity index of 7, which can considered as finished compost, but it further require few more days for further maturation.

Mixed organic waste composting using rotary drum composter

A combination of vegetable waste, cattle manure and saw dust was utilised for high rate composting in a household rotary drum composter. It was found that temperature remained above 55?C for a period of two days, Faecal Coliforms and Faecal Streptococci decrease from 7.5 ? 108 to 5 ? 102 and 1.5 ? 107 to 5 ? 103 bacteria/g, respectively. Negligible VFAs production indicated full aerobic conditions. Nitrification occurred after sixth day i.e., when temperature dropped below 40?C. BOD/COD ratio decreased up to 12 days and remained stable thereafter, indicating the stability of compost in terms of biodegradation.