S.A Abbasi

Potential of two epigeic and two anecic earthworm species in vermicomposting of water hyacinth

The potential of two epigeic species (Eudrilus eugeniae Kinberg, and Perionyx excavatus Perrier) and two anecic species (Lampito mauritii Kinberg and Drawida willsi Michaelson) of earthworms was assessed in terms of efficiency and sustainability of vermicomposting water hyacinth (Eichhornia crassipes, Mart. Solm.). In different vermireactors, each run in duplicate with one of the four species of earthworms, and 75 g of 6:1 water hyacinth:cowdung as feed, vermicasts were produced with steadily increasing output in all the reactors. E. eugeniae was by far the most efficient producer of vermicasts, followed by the other epigeic P. excavatus. The two anecics came next, with D. willsi being the least effective which could generate only about half the quantity of vermicasts achieved in a corresponding time by E. eugeniae. In all the reactors, the earthworms grew well, increasing their weights by more than 250%. The maximum net gain of weight (average 30.7 g) was by E. eugeniae, followed by P. excavatus, L. mauritii and D. willsi. This trend, which followed the efficiency of vermicast production, was also shown in terms of reproductive ability as measured by the number of offspring produced by the four species.

Effect of the application of water hyacinth compost/vermicompost on the growth and flowering of Crossandra undulaefolia, and on several vegetables

The impact of the application of compost/vermicompost obtained from water hyacinth (Eichhornia crassipes, Mart. Solms) on plants was assessed in terms of growth and flowering of the angiosperm crossandra (Crossandra undulaefolia). Overall nine morphological, size, and yield attributes were studied in crossandra saplings raised on water hyacinth compost or vermicompost as compared to the untreated saplings. Application of vermicompost led to statistically significant improvement in the growth and flowering of crossandra compared to the untreated plants. The impact of compost was also beneficial but a little less distinct than the positive impact of vermicompost. Qualitative studies were simultaneously conducted in five kitchen gardens owned by farmers near Pondicherry. In three of these locations water hyacinth vermicompost was applied-and no other fertilizer-for months to different species of vegetables. Water hyacinth compost was similarly applied in another two locations. In all the locations no adverse effect on any of the plant species was observed. We believe these studies would help in dispelling the apprehension of farmers that compost/vermicompost obtained form a pernicious weed like water hyacinth may have deleterious effect on other plants.

Screening of four species of detritivorous (humus - former) earthworms for sustainable vermicomposting of paper waste

Four species of detritivorous (humus – former) earthworms were tested for their ability to vermicompost paper waste blended with cowdung in 6:1 (w/w) ratio. The anecic Lampito mauritii, Kinberg and the epigeic Eudrilus eugeniae, Kinberg were the most effective of the four species employed; 20 animals of each of these species generated castings amounting to about 52% of the feed mass (75 g) per fortnight. The performance of these two species was followed by the anecic Drawida willsi, Michaelsen and the epigeic Perionyx excavatus, Perrier; they achieved approximately 46% vermiconversion in comparable settings. The vermireactors were sustainable as the animals have remained consistently healthy and reproductive over a period of six months, and are continuing to remain so, turning in a steadily rising vermicast output. During this period E.eugeniae have grown to 2.3 times their original weight while the other three species have more than trebled their weights. The studies establish the feasibility of vermicomposting as a viable process for the gainful utilization of paper waste in an environmentally clean manner. They also indicate that all the four species of the worms screened by us are suitable for the process, with L.mauritii and E.eugeniae a shade more efficient than the other two species.

Vermicomposting of the leaf litter of acacia (Acacia auriculiformis): possible roles of reactor geometry, polyphenols, and lignin.

Vermicomposting of the pre-composted leaf litter of acacia (Acacia auriculiformis) was studied in reactors of identical volume but with surface area: height ratios varying from 4 to 250. In separate sets of experiments with these reactors, epigeic earthworm species Eudrilus eugeniae and anecic earthworm species Lampito mauritii were employed at densities of 75 and 150 adult animals per litre of reactor volume. The results reveal that greater the surface area: volume ratio of the reactor, higher is the vermicast output in terms of vermicast output per animal; the more densely populated reactors were comparatively under-productive. Even as the vermicast production remained consistently high in all the reactors, there was significant earthworm mortality throughout the course of the experiments and the worms who survived, steadily lost weight with time. A detailed investigation of the possible causes revealed that, whereas the C:N ratio of acacia compost was comparable with that of other substrates; the polyphenols and lignin content were much higher. Studies by other authors on leaf litter consumption by earthworms in natural or man-made forests have indicated that leaf litter rich in polyphenols and lignin are not preferred by most species of earthworm. This may perhaps be the reason for the high rate of mortality and weight loss in earthworms forced to feed upon acacia in the experiments conducted by the authors.

High - Solids Anaerobic Digestion for the Recovery of Energy from Municipal Solid Waste (MSW)

Anaerobic digestion of municipal solid waste (MSW) was studied in ‘high solids digesters’ (HSDs) for generating energy (as methane). Three kinds of HSDs were employed in which the waste along with inoculum (consisting of pre-digested cow dung slurry) were subjected to anaerobic digestion. The first type (HSD-I) was provided with two chambers; the upper chamber served as a solid phase in which only the solid portions of vegetable waste were subjected to digestion, while the lower chamber served as liquid phase where the leachates were allowed to ferment. The second type (HSD-II) was similar to HSD-I but had no partition. The third type (HSD-III) had two distinct units, one for solid phase and the other for the liquid phase; the units were connected by a tap with a flow regulator valve. The reactor performance was assessed in terms of biogas yield. The results of the study indicate that the performance efficiency (in terms of biogas yield) of the HSDs increased with the increase in the degree of phase separation. The performance of the digesters was further enhanced by providing additional props to facilitate biodegradation, such as biofilm support systems (BSS) in the liquid phase unit/chamber of the HSDs.

Enhancement in the treatment efficiency and conversion to energy of dairy wastewaters by augmenting CST reactors with simple biofilm support systems

Dairy wastewaters are rich in organic carbon and nutrients. When disposed without proper treatment they cause severe pollution of water and land. But if treated by anaerobic fermentation such wastewaters can yield useful clean energy in the form of methane. The systems commonly used for such fermentation throughout the world are Continuously Stirred Tank Reactors (CSTRs). We describe attempts to upgrade CSTR performance by incorporating biofilm support systems (BSSs) within the existing reactors. The focus of the work has been to find inexpensive and easy-to-install BSS which could significantly enhance the rate of waste treatment as well as quantum of energy recovery (as methane). Our experiments with various BSS options have revealed that rolls of nylon mesh (∼1mm openings), of 5 cm height and 2 cm dia, when incorporated in CSTRs at the biofilm-surface : digester-volume ratio of 0.3 cm2 cm−3, enabled the CSTRs to perform better with up to 25% improvement in methane yield. The studies, thus, reveal that simple devices of the type used by us as BSS can significantly improve the performance of CST anaerobic digesters treating dairy wastes. The enhancement is evidently due to the development of active biofilms on the BSS which not only enhance the contact of the water with micro-organisms but also reduce microbial washout. Further, such devices are inexpensive and very easy to incorporate - the gains are thus achieved with very little cost and effort. BSSs were also found by us to enhance conversion of volatile fatty acids – derived earlier by us from aquatic weed water hyacinth – into methane-rich biogas.