Soil Biotechnology for sewage treatment

Comparative study of BMW treatment methods used in the present study

Earthworm growth: After the completion of each of the two cycles of vermicomposting, average individual weight of earthworms, number of recovered cocoons, adults and juveniles were recorded along with total earthworm biomass. The harvested compost was weighed and the yield from each tank was recorded. Physical and chemical properties of vermicompost and natural compost were also estimated.

Storage studies on harvested vermicompost and control: Harvested natural compost/vermicompost from each tank was stored in clean polyethene bags and checked for microbial pathogens namely E.coli, S.aureus, S.typhi, P.aeruginosa, B.cereus, B.subtilus and Klebsiells species. Enumeration of the pathogens in harvested compost and vermicomposts was done for a period of 30 days with an interval of 10 days using standard techniques and growth media.

Common Methods of Treatment & Disposal

Some of the common modes of treating bio-waste in most hospitals are based on the bio-medical waste management and handling rules 1998(11). The following treatment and disposal are practised:

Incineration

The success of the incineration process depends on the quality of the incinerator –capacity, make and its type. Today, only double chambered incinerators are allowed with chlorinated disinfectants. Chlorinated plastics should not be incinerated. The fuel used should be low sulphur Diesel/LDO. The Stack Height should be fitted with scrubber/pollution control device. Ashes need to be disposed of properly in the secured landfill. Aesthetics of treatment facilities should always be highest.

In Delhi, the Government and major private hospitals have their own arrangement for treatment of bio-medical waste. At present there are 18 incinerators, 18 autoclaves and three microwaves in operation in Delhi. Delhi has total incinerator capacity of 2675kg per hour which is more than sufficient if proper segregation is done at source of generation of bio-medical waste.

Autoclaving

There are two kinds of autoclave available in the market: gravity flow and vacuum flow. This works on the wet heat sterilisation mechanism. Gravity flow Autoclave works on the following parameters:

1. Temp >121°C; pressure 15psi; residual time >60 minutes
2. emp >135°C; pressure 31psi; residual time >45 minutes
3. Temp >149°C; pressure 52psi; residual time >30 minutes

Vacuum Autoclave works on following parameters:

1. Temp >121°C; pressure 15psi; residual time >45minutes
2. Temp >135°C; pressure 31psi; residual time >30 minutes

Sterilisation monitoring and validation test are done to verify the efficacy of the autoclave. Wet heat sterilisation is considered to be cost effective and pollution free treatment technology for infectious waste.

Use of Microwave

This process cannot be used for cytotoxic, hazardous or radioactive wastes, contaminated animal carcasses, body parts & large metal items. Use of metal detectors and scintillators is required for microwaves. Efficacy test/routine test are similar to autoclave. Performance guarantee by supplier before operation is essential as it may malfunction more frequently.

Mutilation

The waste should be disposed off after proper mutilation to make it unrecognisable. The shredder should be covered, spillage & sound proof and ergonomically designed. There should be no illegal recycling/reuse of water. For sharps and needles inside the wards there should be needle destroyer. We need to ensure its availability, working conditions, usage, electric supply, proper connections, ergonomics, adequate quantity purchased, issued and service points, continuous maintenance and repair. The shredders in Delhi government hospitals lack conveyer belts.

Ergonomics or Human Engineering

This refers to the design of machines, systems, work methods and environments to take into account the safety, comfort and productiveness of human users and operators. It is mutual adjustment of man and machine, seeking to ensure that the tools and machines are operator friendly. The equipment need to be ergonomically designed and aesthetically used.

Effluent Treatment Plant (ETP)

Effluent treatment plant is required to maintain the standards of liquid waste. The quantum of liquid waste generated in Europe is 1000lt per patient per day (3-5 times more than standard citizen) whereas quantum of liquid waste generated in Delhi is 1470lt per bed per day. The effluent generated from the hospital should confirm to the following limits:

Centralised Bio-Medical Waste Treatment Facilities (CBWTF)

Total number of CBWTF operating in the country is about 143. The average number of healthcare facilities per CBWTF are 508 and average number of beds catered by CBWTF are 6606. There are three large operators of CBWTF: EA Infrastructure Operation Pvt Ltd, Mumbai; SembRamky Environmental Management Pvt Ltd, Ludhiana; and Synergy Waste Management Pvt Ltd, Delhi.

Bin Bags Demystified

People often get confused by what is and what is not recyclable. Here’s a quick guide to the differences between fully biodegradable/compostable, PE (polyethylene) and ‘oxo-biodegradable’ bin bags.

There are three types of bin liners currently available:

1. Fully biodegradable liners made from corn starch (or other crop derived sources) and polylactic acid, designed to biodegrade in aerobic, home or industrial composting conditions. These liners will be completely consumed by micro-organisms in the food chain and are 100% compostable and biodegradable.
2. Standard PE plastic bin liners made from polyethylene or similar material derived from oil and suitable for incineration or landfill disposal. Fully recyclable, plastic liners are increasingly being re-used by consumers.
3. Degradable PE liners, sometimes also known as ‘Oxy-biodegradable’ (or ‘UV biodegradable’), are made from oil derived PE but also contain a special metal additive (typically cobalt, nickel or manganese stearate), which acts as a catalyst to enable the plastic to degrade by oxidation and exposure to light and heat. This reduces the material to trace metal elements – which do not break down or biodegrade – CO2 and water. These liners can take between 18 months and four years to disintegrate according to conditions and only if left in an open atmosphere, and are unlikely to fully degrade if buried in landfill sites. These are not considered to be any more environment friendly than standard PE bags.

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