Eco-friendly
Ways of Bio-Waste Disposal
Besides the common methods of treatment and disposal of bio-medical waste (BMW), which are tried and tested successfully by experts there are also vermicomposting process with encouraging results. A study…
Improper disposal of medical/hospital or bio-waste introduces pathogens into the environment. The bacteria or viruses transported in the waste get introduced to new areas causing deadly diseases. Waste acts as a food source or breeding ground for pathogens which turns hazardous when the waste is human biological material or other bio-waste. Viruses causing hepatitis & HIV and bacteria causing tuberculosis are more commonly found in medical environments but may exist in common waste and can grow in bio-waste from any source. Some of the common methods of disposal include incineration, autoclaving and microwave process.
A study was carried out to evolve an environment friendly method to treat biodegradable bio-medical waste collected from local hospitals using vermicomposting. Results revealed that the vermicomposting of BMW was comparatively more efficient than natural composting. The performance efficiencies of earthworms in different treatments were as follows: Eisenia fetida > Mixed culture > Eudrilus eugeniae > Perionyx excavatus. It was also found that repeating the same set of earthworms for successive cycles showed improved rate of vermicomposting. Since the complexity and toxicity levels of BMW produced at different hospitals vary, it is recommended to treat BMW by vermicomposting using a mixed culture of all three epigeic earthworms. It is also essential to gradually expose them to the waste to make them adapt to this toxic material. Vermicomposting with proper handling of BMW can be an energy efficient eco-friendly approach for reducing and recycling of this hazardous waste.
Materials & Methods
Collection of bio-medical wastes: Bio-medical waste (45kg) was collected from KS Hospital, Bangalore, and used as & when required for experimentation. For each of the cycles of vermicomposting, 20kg of BMW was utilised and 5kg of BMW was used as control (natural composting). Only the biodegradable matter of the infected BMW was considered for the experiment. This included blood stained cotton pieces, pus and body fluids, antiseptics/antibiotics used for dressing of wounds, spilled liquid and tissues collected from operation tables. They were subjected to the preliminary treatment onsite to reduce the probable hazardous effect.
Preliminary on-site treatment of BMW: The BMW used for the experiment was chemically sterilized on site using 5% of 1N NaOCI as suggested in previous works. This was done to disinfect the BMW before subjecting it to vermicomposting and natural composting.
Primary decomposition of disinfected BMW: Following the chemical treatment, the disinfected BMW was made palatable or more suitable for the earthworm species to feed. Primary decomposition of BMW was carried out in laboratory for a period of 15 days as follows:
- Preparation of cow dung slurry: A homogenous mixture of cow dung slurry was prepared at 1:4 (w/v) ratios by mixing 250g of cow dung with one litre of distilled water. Five litres of the slurry was prepared and maintained in five separate containers containing one litre slurry in each for further use.
- Mixing of BMW with cow dung slurry: To each of the five containers with one litre cow dung slurry, 5kg of BMW was added and mixed (at 5:1, BMW: cow dung slurry ratio w/v). The mixture was allowed to undergo primary decomposition for a period of 15 days in the laboratory. The same procedure was carried out to prepare the control tank. It was also done to facilitate the consumption of BMW by epigeic earthworms during the process of vermicomposting. The process of preliminary on site treatment and primary decomposition was carried out for every fresh batch of BMW used for vermicomposting.
Tank Preparation
Preparation of tanks for vermicomposting and natural composting: Four plastic tanks were maintained to carry out the process of vermicomposting. Each tank used for the experiment measured one metre long, 0.5m broad and 0.5m deep. A tank containing only 5kg primary decomposed BMW but without introduction of any earthworm species was maintained as control and allowed to undergo natural composting for a period of 45 days. The mix used for the study to begin with was measured for pH, moisture content and temperature. The initial measured pH was 6.3, temperature 25°C and 60% moisture.
Collection of suitable epigeic earthworms: The epigeic earthworm species, namely Eisenia fetida, Eudrilus eugeniae and Perionyx excavatus were used for the study. These species were collected from the Department of Agricultural Microbiology, University of Agriculture, Bangalore.
Release of earthworms into tanks: To each of the four tanks maintained for vermicomposting, 5kg of primarily decomposed BMW (previously prepared and maintained in laboratory) was added. Three tanks were used as monoculture tanks (single species per tank) while one was used as a polyculture tank (all three species in tank). Hundred adult earthworms each of Eisenia fetida, Eudrilus eugeniae and Perionyx excavatus were released into the monoculture tanks respectively. The polyculture tank had 33 adults of each of E.fetida, E.eugeniae and P.excavatus. After the first cycle of vermicomposting, the recovered/survived earthworms (both adult and juveniles) from the respective tanks were used for another cycle of vermicomposting (45 days) using fresh primarily decomposed waste.
