Tuesday, 23 October 2018

Water Positive Campus

What is Water Positive Campus?

“A commercial or residential developments are said to be water positive when they are creating more water than they are using.
“A water positive campus produces more water than it consumes.”

How can it be Achieved?

There are three ways by which campus can become water positive:

1) Rainwater Harvesting: We have already discussed earlier rainwater potential in India. Harvesting rainwater is the simplest way to conserve water. This water can be used for drinking and other purposes after treatment or it can be transferred to GW recharge pit for groundwater recharge.

2) Wastewater treatment, Recycling and reuse: Recycling wastewater after treatment is next step towards being water positive. About 50 percent of domestic wastewater generated can be reused after treatment. For an efficient treatment, microSTP is a electro-coagulation based low-cost treatment plant which can be installed in small homes to large campuses.

3) Optimizing Water Use: It means reducing the amount of water you consume by installing water-efficient appliances, taps and fittings or limiting your water usage. For an example, replacing ordinary tap with tap aerator can save as much as up to half your water usage. Adopting sensor-based irrigation system (SMART DRIP) for home-garden can save up to 95 percent of water.

Example: A college hostel has the strength of 300 students who stay in the hostel for 300 days a year. The per capita water demand of students is 125 Liters/day. College campus has a rooftop area (5,500 m2) and green area (16,500 m2) available.  The average rainfall in the region is 900 mm.  Is this campus have the potential to become water positive?

Why it is Important?

In India, freshwater resources are depleting every year. Today India is water-stressed and moving towards what's technically termed “water scarcity condition” with a majority of the country. Water positive campus is a sustainable concept which can overcome the water crisis in future in a greener way! 

Wastewater Generation, Treatment and Reuse

In India, wastewater generation from all class-I cities and class-II towns is 38254 MLD and treatment capacity is 11787 MLD, which is about 30 % of total sewage. About 70% of wastewater remain untreated and discharged in water streams like rivers and ocean leaving them polluted.

Average domestic water consumption pattern
In urban India, about 48,000 MLD water is supplied and on average a person uses 165 litres of water per day. The chart and table below show the break up of per capita domestic water use pattern.

Micro STP for Greywater Treatment and Reuse
Greywater is wastewater from non-toilet plumbing fixtures such as showers, basins and taps. Almost 50% of the water supplied for domestic use, comes out as greywater.

         Micro STP is small-scale sewage treatment plant designed for the domestic greywater treatment. Treatment processes, it may employ biological, chemical, mechanical or electrochemical means. The treated water should be free from any kind of harmful bacteria/pathogens, therefore, in addition, disinfection systems may also require with this system, if water is reused indoors.

               Treated greywater can be reused for toilet flushing and laundry which are two of the biggest consumer of the water in an average household. Apart from this,  it can also be reused for other purposes like gardening, car washing, floor mopping etc. Reusing greywater after treatment can reduce per capita water demand by 50 percent or about 80 litres/day.

Environmental Impact
Centralize wastewater treatment is a big challenge as one of the largest issues facing wastewater management facilities is energy consumption. Wastewater treatment consumes almost 3% of the developed nation’s electrical power annually. That is a large expense for the wastewater industry alone. Why not treat the wastewater at a point source and reuse it. Onsite water reuse can not only reduce per capita water requirement but also help in reducing environmental footprint by suppressing the water pollution.

Rainwater Harvesting Potential in India

Water has been considered as a free resource for years. With the rapid growth in population and increasing demand for water on one hand and depletion of available water on the other has led India to acute water stress. This article explains the rainwater harvesting potential in India and how it can save us from becoming water scare nation.

Rainfall In India
On average, India receives about 4,000 cubic kilometres of rains annually or about 1,720 cubic metres of fresh water per person every year, out of which 700 cubic kilometres is immediately lost of the atmosphere, 2150 cubic kilometres soaks into the ground, and 1150 cubic kilometres flows as surface run-off.
More than 70 % of annual rainfall occurs during its monsoon seasons (June to September), with the northeast and north receiving far more rains than India's west and south. India currently stores only 6% of its annual rainfall or 253 billion cubic metres, while developed nations strategically store 250% of the annual rainfall in arid river basins.

Water Demand and Resources
India dedicated about 688 cubic kilometres (84%) to irrigation, 56 cubic kilometres (7%) to municipal and drinking water applications and 69 cubic kilometres (9%) to industries and other applications.

Other than rains, the melting of snow over the Himalayas after winter season feeds the northern rivers to varying degrees. India also relies excessively on groundwater resources, which accounts for over 50 percent of the irrigated area.

Rainwater Harvesting Potential
Based on average annual rainfall and water demand, India has great rainwater harvesting potential to fulfil water needs of all the sectors alone. 

Water Demand in km3
Rainwater Utilization(When 80 % rainwater is harvested)
688910107220.9 %27.5 %32.4 %
Drinking Water
56731021.6 %2.2 %3 %
Industry & Others
691102732 %3.3 %8.3 %
8131093144725 %33 %44 %

Way Forward
It is clearly extrapolated that not even 50 % of rainwater is utilized on combing all the sectors water demand by 2050. This is just rainwater, we have other water resources too. India just needs a proper water management and it will never run out of water for at least 100 years. Water conservation, it all starts with us. Individual contribution is important to protect our natural resources. Use water precisely and save it to use it tomorrow.