Soil Biotechnology for sewage treatment

A viable and cheap alternative for sewage treatment – Soil Biotechnology (SBT) – helps communities tackle water problems in a more cost effective way

An ecological method – Soil Biotechnology (SBT) based STPs – researched for over two decades at IIT-Mumbai, provides clean river quality water at a low cost. Vision Earthcare, incubated in IIT Mumbai, has licensed this method for deployment globally.

STP treats domestic wastewater for disposal. However, apartments and gated communities situated away from the city are totally dependent on bore wells or water tankers. It is mandatory for them to have their own STPs. River water for such communities is a distant dream. Hence, the realities are forcing them to look upon their wastewater output as an abundant new source of water. Some communities have started reusing their treated water for flushing and gardening although there are serious problems with the quality of the treated water. Most STPs in communities are Activated Sludge Process (ASP) based.

Conventional Technologies

In conventional technologies such as ASP, aeration is achieved mechanically, which is very energy intensive. At higher ambient temperatures (like in India) the solubility of oxygen in water is low and therefore, energy requirement increases.

Moreover, air contains only 20% oxygen, the rest being nitrogen that is passed into water wastefully, further adding to process inefficiency. In addition to these inherent limitations of the method, several additional reasons make the reality worse. Treat it somewhat; dump it somewhere is the usual story in most communities.

While interacting with a community in South India, Dr Chandrashekar of Vision Earthcare highlighted several important points that surfaced during the interaction . Some of them were:

1. Conventional STPs are designed for disposal rather than for reuse.
2. They are overloaded, poorly maintained and are prone to frequent breakdowns and are also usually operated by unreliable vendors who employ unskilled labourers as “STP operators”.
3. In addition to a hefty monthly fee, vendors pressurise communities to replace pumps, motors fairly often (to obtain ‘commissions’).
4. There is also significant monthly electricity cost for running STPs.
5. Many communities do not perform an independent quality test of treated water. Vendors usually rig the tests to fake compliance with Karnataka State Pollution Control Board (KSPCB) standards. Foul odour is very common.

Thus, STPs in most communities not only consume large amount of resources but also pollute surface water bodies and eventually our only source, ground water, when partially treated water is dumped onto open lawns or into storm water drains. Vendors pocket large sums and tanker mafias continue to benefit because of increasing demand for water, while communities grapple with water shortage, pollution and flooding.

Soil Biotechnology (SBT) based STPs

SBT is a major paradigm shift in waste processing. Sewage treatment is just one application among many – it can be used for arsenic/iron removal, hospital waste processing, industrial wastewater processing & air purification and so on. Because of its versatility, it revolutionises the way we look at wastewater.

SBT treats water for reuse rather than disposal. Since it reinforces the carbon and nitrogen cycles in nature, the quality of the treated water exceeds KSPCB standards reducing Chemical Oxygen Demand (COD) nitrates to very low levels unlike any other STP method. It is highly scalable and can be designed for houses, apartments, gated layouts, towns or cities. The treated water can be reused in many ways:

• Can be sold to constructions/industries who normally purchase tankers. Plant costs can be recovered within a few years depending on the amount of reuse.
• Can be piped back to homes for flushing toilets, gardening, washing yards, cars which can be almost 50% of daily requirements.
• Can be used to recharge groundwater using rainwater harvesting recharge wells.
• Acts like virtual rain when you want it, where you want it, how much and at the required rate.

Ecologically Safe

SBT is a patented method (US and Indian) developed by Prof HS Shankar, Department of Chemical Engineering, IIT Mumbai. It uses only natural materials, natural agents (bacteria culture, worms) and natural processes (respiration, photosynthesis, nitrogen fixation) – it is ecologically 100% safe.

Unlike a conventional STP or septic tank where periodically the sludge has to be offloaded, everything is consumed within the plant in this SBT based STP. Raw sewage is pumped to a customised media bed for around five hours (dependent on load and capacity) and clean water flows into the collection tank.

It has at most two motors, unlike conventional ASP based STPs with numerous motors, stirrer, blower, reverse flush tank, clarifier, sludge pumps and so on. Hence, it is energy & cost efficient and requires minimal maintenance while being more reliable.

The recurring cost consists of natural materials used as additives and it can be operated by gardeners rather than environmental engineers. Life of the specially constituted filtering media bed is long (tens of years) since with time the natural living agents multiply or shrink to optimal levels based on the actual chemical and biological load in the system. Unlike other ecological STP methods it is far more space and time efficient.

Many communities who have ASP based conventional STPs may hesitate to replace it with a brand new one. Consider these:

1. Your existing STPs are expensive (maintenance, operation) while not providing any water for reuse.
2. Rainwater harvesting investment can be leveraged with SBT for storage, reuse and recharge on a daily basis, all year.
3. If you purchase water tankers for consumption, the yearly cost would pay for a new SBT plant.

In conclusion, the fundamental process accomplished by any STP is taking impurities to the highest oxidised state. Since SBT processes waste on land rather than inside water, it is inherently superior to all the current STP technologies in installation, operation, effectiveness and longevity. For water security, SBT is a must and a blessing.

Citizen Matters, Bangalore

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.

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.

Journal of the Indian Society of Hospital Waste Management

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.

Cleanzine