Greywater recycling for toilet use

A study on greywater recycling solution for toilets done at a hostel for tribal students in Maharashtra shows significant improvement in sanitation and cleanliness.
Triple benefits of JalSevak.
Triple benefits of JalSevak.

JalSevak Solutions present a feasibility study for implementation of JalSevak greywater recycling system at a tribal students' hostel in rural Maharashtra. We analyse the present conditions, existing water supply infrastructure, possible design of the greywater recycling solution and potential benefits.

VKA hostel building

Background

Vanavasi Kalyan Ashram, Maharashtra (वनवासी कल्याण आश्रम, महाराष्ट्र) is a non-profit organisation (NGO) working for the welfare of the tribal people in Maharashtra. It especially focuses on providing education to the tribal students and runs several hostels across the state and the country. Boys and girls belonging to nomadic tribes (adivasis) are accepted and accommodated in these hostels. One such hostel is located at a settlement called Chinchavali, 12 km from Panvel and 50 km from Mumbai. As of August 2016, 36 tribal students of age 10-16 reside in the hostel along with four support staff.

Present water situation

Though only 12 km away from the Panvel city, Chinchavali area has chronic water shortage. A seasonal river flows nearby in monsoon but gets completely dried up by December. The only source of water for the community is a well run by the gram panchayat that distributes water to its residents. The well has adequate water during and after the annual monsoon. By December, however, the water level in the well starts declining. From December till the June of next year, residents have to either rely on borewells (which too run dry) or expensive water from water tankers.

 Current water consumption at hostel

BreakupDuring monsoon period, the hostel receives around 2500 litres per day of water supply. At 62.5 litres per day per capita, this water supply is less than half of the 135 lpd as suggested by Indian standard 1172. A quick breakup of water consumption activities is given. Most important activities include:         

  • Cooking and drinking: 42 percent or 1050 litres
  • Bathing and washing clothes26 percent or 650 litres (there is no washing machine in the facility and the students wash their clothes by hand)
  • Utensil cleaning14 percent or 350 litres
  • Toilet18 percent or 450 litres

This breakup indicates that sufficient water is not available for flushing out waste in the toilets. Moreover, since this is the best case scenario of water supply (2500 litres per day), water consumption for flushing toilets is expected to reduce from 18 percent to less than 10 percent during summer months. This results in severe lack of sanitation and well-being of the students.

Current layout of toilets and bathrooms

There are four bathrooms, toilets and washing sinks each at the hostel. There are squat toilets with no flush tanks. Water is poured manually after use which results in inconsistent cleanliness and hygiene.

Toilets and bathrooms

a) Present arrangement of bathrooms and toilets on the campus; b) Indian-styled toilets with no flush tanks.

Discharge from all the bathrooms and sinks is not connected to sewage line and is discharged into the open space behind the bathrooms. This leads to long term hazards from sewage accumulation.

Bathroom open

Backside of the bathrooms showing discharge pipes dumping water into backyard

Greywater estimates

From the breakup shown above, the daily greywater production is estimated to be roughly 1000 litres (bathrooms + utensils washing). This greywater, presently discharged into the open, can be collected and reused for toilet flushing; 18 per cent fresh water that is currently used for toilet needs can be saved. Schematic layouts of current practice and proposed solution are given below.

current

Schematic showing layout of existing water and wastewater piping


 proposed

Schematic showing layout of proposed water and wastewater piping

 

Potential benefits of implementing greywater system

Channeling the greywater back for toilet flushing will offer these significant benefits:

  • Saving 18 percent (450 litres/day) freshwater
  • Double the amount of water available for toilet flushing (from 450 litres/day to 1000 litres/day)
  • Reduction in open drainage (1000 litres/day)

Additional benefits of implementing such a system are:

  • Significantly improve sanitation and well-being
  • Improve resilience against water shortage
  • Potential for increase in number of students due to availability of water
  • Additional water available for gardening, agriculture

Project cost

This project shall require refitting all four toilets with western-style commodes for better cleanliness and hygiene. Plumbing modifications are easy and shall not require replacing any pipes. Table 1 gives a high-level costing for installation of JalSevak greywater recycling system and table 2 gives approximate operating cost.

 

Table 1 - Installation cost

ITEM

COST
New toilets with flush tanks (4 qty) ₹ 10,000
Plumbing to collect greywater ₹ 30,000
1500 litre capacity JalSevak greywater system
Plumbing to connect to 4 flush tanks

 

Table 2 - Operating cost

ITEM

COST
Electricity cost 1 kWh per day
Sanitizer refill ₹ 5 per day

 

Economic Impact

As mentioned previously, the hostel has to survive on water tankers for five to six months in a year. A water tanker of 10,000 litre capacity costs approximately ₹2,000, making the water cost to be 20 paise/litre. Conserving 500 litres of fresh water per day would result in a saving of ₹100 per day. Subtracting ₹10 per day as operating cost, the net daily saving for the hostel is ₹90 which is ₹32,500 per annum. With the total system cost at ₹40,000, the simple payback period is one year four months, assuming a full year on tanker water supply. So in reality the payback would be two years eight months (since tankers are needed for only six months per year). To summarize:

  • Daily water savings: 500 litres
  • Daily water cost savings: ₹90
  • Monthly savings: ₹2,700
  • Simple payback period: Two years, eight months

Sanitation Impact

  • Cleanliness shall be improved by 100 percent
  • Open sewage shall be reduced by 100 percent

Conclusions

We have conducted a feasibility study of installing JalSevak greywater solution at a tribal hostel in Maharashtra. The study shows that reusing bathroom and sink water for flushing and cleaning toilets results in significant impact on fresh water conservation (500 litres/day), sanitation improvement (by 100 percent) and reduction in open sewage (by 100 percent). The modifications involve refitting all toilets with western style commodes having flush tanks. A total cost of ₹40,000 is envisaged and return on investment is estimated by two years and eight months. Besides these benefits, the well-being of these underprivileged children can be significantly improved.

 

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