Why Waste Waste Water?

"Water, water, every where,

Nor any drop to drink."

The ballad of  ST Coleridge proclaims centuries back. The vision and the warning have come true in the beginning of this 21st century. Either the world suffers from its excess or its shortage or  for the poor quality. But the world has already started to feel and many reel in thirst.  No more deserts alone suffered without water and nomads searching for oasis. Today every one has to go out with a water can without fail. 

Are we taking steps to stop this dangerous trend?

Definitely not.

Chennai  and the neighboring Chengalpet were known  for their lakes of varied sizes in thousands and in Chennai today just in three places stagnant water is stored and we call them as 'lakes'.

This sea change is invisible to all the visible. The irony is that we all  have Lake View Roads' everywhere. Of course the biggest lake is  there for us but the water is salty and they call it as ocean.

The Rain water harvesting system which was in vogue a decade back has decayed  and people have  linked their drainage lines with these facilities which are supposed to carry storm water. 

Now what can be done.

Waste water is defined as “a combination of one or more of: 

•  Domestic effluent consisting of black water (excreta, urine and faecal sludge) and grey water (kitchen and bathing waste water);
•  Water from commercial establishments and institutions, including hospitals; 
• Industrial effluent, storm water and other urban run-off;
• Agricultural, horticultural and aquaculture effluent, either dissolved or as suspended matter” (Corcoran et al. 2010). 

Wastewater can act as a: 

• Drought-resistant source of water (especially for agriculture or industry);
• Source of nutrients for agriculture; 
• Soil conditioner; and
• Source of energy/heat.

Drought resistant source of water 

The use of reclaimed wastewater in agriculture can provide a reliable source of irrigation water for farmers. Cities have been described as ‘sponges’ soaking up water from other areas (Amerasinghe et al., 2013) and, as noted in FAO (2010), at times of scarcity, authorities often divert water from farmers to cities as water used for urban and industrial purposes tend to have a higher economic value than that used for most agricultural purposes and, obviously, supplies for human consumption take priority over other uses. In developed countries, waste water is often used to irrigate non-agricultural land, such as parks, golf courses and highway verges or to replace drinking water used for toilet flushing.

Source of nutrients 

Waste water is nutrient-rich and can reduce the need for the application of chemical fertilizers. Phosphorus, for example, is essential to all life and is a key component of fertilizers. The main source of phosphorus (phosphate rock) is non-renewable and is becoming increasingly expensive. Human faeces, however, contains about 0.5% phosphorus by weight and recovery/reuse could improve phosphorus security and reduce pollution (Cordell et al., 2011). 

Source of energy/heat

 Anaerobic digestion is a bacterial decomposition process that stabilises organic wastes and produces a mixture of methane and carbon dioxide (known as bio gas), which is a valuable energy source. Anaerobic digestion is usually carried out in a specially built digester and is common at some waste water treatment works. The use of faecal sludge as a fuel has also been investigated in developing countries. Muspratt et al. (in press), for example, collected sludge samples from pit latrines, septic tanks, drying beds and stabilization ponds from Ghana, Uganda and Senegal for the determination of calorific value. The average calorific value of the sludge was 17.3 MJ/kg total solids which compares well with other biomass fuels, although partial drying of the sludge was required. 

Soil conditioner 

When faecal solids are properly treated and of good quality they can be used on agricultural land or gardens as a soil conditioner/fertilizer and are often termed ‘bio solids’.Soil conditioner may be produced on a variety of scales from municipal waste water treatments plants down to individual households practicing ecological sanitation.