One of the first questions that intrigues and troubles us is why should we be burdened with water treatment, when it is the responsibility of the Municipal Corporations.
To put things into perspective, it is important to understand that the reality is a bit harsh to take.
For one, we have a major fresh water scarcity issue, and secondly, most of our water bodies are extremely polluted.
The scale of cleaning up India is huge and if we take some responsibility, it will keep these issues from becoming even bigger.
From a regulatory point of view, it is now mandatory for communities to invest in STPs as only decentralized action can reduce the overall burden on water resources.
The issue then is to determine what works well for communities now and throughout the life of the building. The first step is to know what really comes out of a household in terms of wastewater.
Usually, fresh water plus the contamination of soap, dirt, oil, washing detergents and liquids, or cleaning agents is called grey water. Water that comes out of the toilets systems is called black water.
In the grey water, many contaminants are bio-degradable. When these get degraded, they use oxygen in the process. There are some others that are chemical in nature and yet, use oxygen for degradation.
The water becomes oxygen deprived, which is measured through certain lab tests called BOD ( Biological Oxygen Demand) and COD ( Chemical Oxygen Demand).
Black water also has a high level of Total Suspended Solids (TSS) and bacteria such as E. Coli.
Typically the aim of an STP is to change the quality of water, so that the parameter values are changed.
If the water is sufficiently oxygenated and treated to ensure bacterial contamination is within limits, the water can be used for non potable purposes such as gardening.
A conventional STP in a community can sometimes become a nightmare for residents to maintain once the builder’s maintenance period is over.
Apart from issues of poor performance when the STP is not working under its full capacity, it also requires expensive equipment like aerators, digestors, pumps, etc. Add to that the cost of maintaining these systems, which is about 10-15% of the initial cost of these systems.
A plant-based system, called Phytorid, has some of the advantages that conventional STPs do not have.
In the Phytorid system, oxygen need not be pumped as that requirement is fulfilled by the plants that supply oxygen for the bacteria and ‘digest’ the nutrients.
In the Phytorid system, the sludge generated is minimal, while conventional STPs generate significantly more sludge, which has to be dried and disposed of.
However, for a Phytorid system, the maintenance cost is just 1-2 % of the initial cost. The land required for the construction of a Phytorid system is less than half that of a conventional activated sludge system.
The best part is that a Phytorid system requires minimal electricity and has no foul odour.
Not to mention, a garden looks much better than a conventional STP!
Being energy efficient while treating water is the requirement of the day as that is what makes this system carbon neutral.
Phytorid is a wastewater treatment technology which uses plants to treat water.
The wastewater flows through a tank that contains plants like Elephant grass (Pennisetumpurpurem), Cattails (Typha sp.), Reeds (Phragmitessp.), Cannas pp. and Yellow flag iris (Iris pseudocorus).
The plants absorb the ‘waste’ in the wastewater as nutrients for their growth.
By the time the water flows out of the tank, it has about 70% to 80% less total suspended solids (TSS), 78% to 84% less BOD, 70% to 75% less nitrogen, 52% to 64% less phosphorus, and 90 % to 97% less faecal coliform.
The system is simple as it has an inlet zone and an outlet zone, and tucked in between is the treatment zone, which has the same plant species as the inlet zone. The inlet zone also has crushed bricks and stones of different sizes.
While the idea of purifying water by absorbing the nutrients can be found naturally and commonly in many wetlands around the world, this particular system was developed by the National Environmental Engineering Research Institute (NEERI), Nagpur.
The cost of construction of a phytorid system is comparable to that of a conventional STP. Both systems have a similar payback period of about 3-4 years.
However, the main difference is that of the maintenance cost. As a homeowner in a villa or an apartment using a Phytorid STP, you could save enormously on the maintenance cost.
Phytorid system requires roughly half the area that is required for a conventional STP.
The Phytorid system is designed in such a way that the wastewater never comes up to the surface of the system. This prevents any foul odour.
A planting substrate covers the surface of the Phytorid system, which acts as a barrier between the wastewater and open air. This ensures that the wastewater is not available as a breeding ground for mosquitoes.
Since the Phytorid system is based on the natural process of water treatment found in wetlands, the maintenance required for it is also minimal.
According to a study published in the International Journal of Advanced Technology in Civil Engineering, the maintenance cost of a conventional STP is about Rs. 16/m3, while that for a constructed wetland (like the Phytorid), it is just Re. 1/m3.
There are communities in Bangalore and other cities, where this system runs successfully.
At one location, for a 250 KL capacity system, the cost of operation and maintenance is about Rs. 10000 per month, including electricity.
Compare this to approximately Rs. 1 lac per month incurred for the operation and maintenance of the 200 KL conventional STP previously used in the same location. There have been no complaints of foul odour or mosquito nuisance.
Instead, the STP looks like a beautiful garden in the backyard.
At the NEERI Zonal Lab in Worli, Mumbai, a 5 KL capacity Phytorid STP has been installed to enable the treatment and reuse of its greywater (water from the kitchen, bathroom, wash basins, etc.). this system has been in operation since 2005.
The operation and maintenance cost is about Rs. 10000 per year, including the cost of pumping the water for use in their garden. As with the Rainbow Drive Society system, the Phytorid system here has not led to any odour problems.
In Mittal Auriga in Bangalore, we have already put a Phytorid System that is working absolutely fine.
The water treated in a Phytorid system has been tested by several agencies at various locations.
In all cases, the water has been found fit for use in agriculture and gardening, as well as for discharge into water bodies.
Compared to conventional STPs, the Phytorid is a fairly simple system of wastewater treatment. It is just that people are not aware of the system.
This technology by NEERI has also been adopted in commercial and residential buildings all over India.
Some of the institutions that have adopted the Phytorid system include Raj Bhavan, Mumbai; Teen Murti Bhavan, New Delhi; Raipur Development Authority, Raipur; and some other private factories.
As more people adopt it, the awareness among people will increase and the advantages of this system compared to the conventional STP will become clearer.
For people wanting a cleaner, economical, simpler, and more eco-friendly option for wastewater treatment onsite, Phytorid is certainly the way to go!