By Kanka Ghosh and Priya Khola
The challenge of having to work with limited resources has been the driving force behind several technological innovations in the past. Today, the need of the hour to develop sustainable solutions for the present and future generations is even higher as the pressure on water resources increases rapidly by the hour. Prof. Ligy Philip and her enthusiastic group of research scholars in IIT Madras are fighting tooth and nail to resolve some unavoidable facets of water-management which has a direct bearing on the wise utilization of water resources at hand today.
Why Bother With Waste-Water?
United Nation reports estimate that globally, around 783 million people [1] do not have access to clean water. In 2010, the United Nations General Assembly recognized access to water and sanitation as a human right and yet we find ourselves continually haunted by physical and economical[2] water crisis with an ever-increasing sense of insecurity (Fig.1). A more recent, WHO- UNICEF report (2014) emphasized that 946 million people globally, still practice open defecation which in turn gives rise to several waterborne and vector-borne diseases such as cholera, diarrhea, jaundice etc.
International Water Management Institute analysis
In India, too the situation is quite miserable. It has been reported that 626 million people in India don’t have proper toilet facilities in households. Another report, based on data from the Ministry of Urban Development (2013) and Central Pollution Control Board, estimates that 75-80 % of water pollution results from domestic sewage and that untreated sewage flowing into water bodies such as rivers has almost doubled in recent years. More alarmingly, in a recent study, WHO/UNICEF Joint Monitoring Program (JMP) for Water Supply and Sanitation has released a ranking of the countries based on an estimate of improvement of sanitation facilities in a time duration between 2000-2015 where India ranks 154 out of 188 countries [3]. In these circumstances, waste-water management is crucial towards providing a sustainable solution.
A Decentralized Route for Sustainability
In ensuring the safe & smooth distribution of resources in a community, wastewater management has always been a challenging undertaking. This is because the outcomes of doing so not only affects the health of the community, but also determines the efficiency of the utilization of water as a scarce resource. Therefore, there is a need for responsible management of waste-water. One of the prominent problems regarding the wastewater management is the modus operandi of the traditionally installed centralized sewage systems. The problems associated with it are manifold in nature. In a centralized sewage treatment system, wastes are collected through the pipeline which connects the centralized treatment plant to the sewer system. In Chennai, there are 6 centralized plants, which collect wastes throughout the city. Transport operations incur high costs and difficulties arise since wastewater is recycled far from where it was collected.
Dr. Phillip along with her scholars from EWRE (Environmental and Water Resources Engineering) division of Civil engineering department have undertaken an alternate decentralized route to resolve these issues. The concept of decentralized sewage-treatment is slowly coming to the front for the need of recycling of water. Prof. Ligy’s group involved in developing different techniques for decentralized systems. Here’s a brief overview:
Prof.Ligy provided rough estimates on the amount of water they are recycling at the IITM wastewater plant, located near the IIT Madras Research Park. ”Daily, we save 8-10 lakh litres of water inside our campus!”, she smiled confidently. Her estimates gave us a glimpse of the magnitude of the problem they are trying to solve. We discuss some of the notable activities of Prof.Ligy’s group in detail in the next section.
Bacteria & Bio-digesters
Started in September 2015 and funded by the Bill and Melinda Gates Foundation is a project titled ‘Monitoring and Evaluating the Onsite Waste-Water Treatment System Comprising of DRDO Based Anaerobic Digestion Units for Toilets in South India.’ It is one of the many projects Prof. Ligy Phillip and her research scholars have been working on. Anaerobic digestion is a series of biological processes in which microorganisms (mostly bacteria) break down biodegradable material in the absence of oxygen. These anaerobic digesters are employed in waste-water treatment plants to break down sewage residues and eliminate pathogens in waste-water. Likewise, the digester units deployed in this project are essentially modified septic tanks. A biodigester is like a mechanical stomach. It is fed with organic material, which is broken down (decomposed) by microorganisms (bacteria) is an oxygen-free (anaerobic) environment to produce a renewable energy called bio-gas (methane and carbon dioxide) and other material that is mainly used as fertilizer. Since all the starting material used are organic, break down of these organic moieties results in simpler organic molecules.
Septic tank systems are a type of onsite sewage facility (OSSF). They are watertight chambers made of concrete, fibreglass, PVC or plastic, through which sewage flows for primary treatment. Water is allowed to stand for a given settling time and later anaerobic processes reduce solids and organics. But the treatment is only moderate and they are used in areas that are not connected to a sewerage system, such as rural locations.
The modified septic tank comes with three compartments with a scrub resembling material forming the base of the tank which increases the activity. It is a microbial consortium a mixture of different bacteria in a fixed composition called Inoculum. The microbes feed on the fecal matter and hence reduce the carbon and nitrogen components into simpler molecules. This technology has been patented by DRDO and as per their claims, Inoculum once added to the biodigester, is enough for a lifetime. As Dr. Kalai Vani, a research scholar at Prof. Ligys lab explains, DRDO makes these anaerobic bio digesters for the treatment of black water i.e. the water which comes out of the toilets and has been able to achieve up to 60-65% treatment efficiency with respect to organic matter removal. This performance is comparable with a septic tank without any inoculum addition. Presently, biodigesters placed in 13 sites across South India are under evaluation with one of the sites being here, at IIT Madras. In order to unearth the science surrounding this innovation, we ventured forth to ask the procedure for evaluation of the biodigester, to which Dr. Kala Vani very patiently explained that they had installed six reactors namely A , B, C , D ,E, F at different locations in the lush green IIT campus with each one being operated under different conditions. Their description is as follows:
In order to routinely monitor the working of the biodigester, the team collects samples from each reactor and tests them in the lab by different techniques. These techniques measure the pH-levels, temperature, dissolved oxygen, ammoniacal nitrogen, fecal coliform and many more constituents by different laboratory techniques. Ground level monitoring results show a removal efficiency of 60-65% against the values of 80-90%, claimed by the vendors.
Running a Decentralized Sanitation System
Next, we had the opportunity of speaking with Mr.Ram Prasad, one of the research scholars in the team who spoke to us about his project – a community-based waste-water management system being carried out in Medavakkam. Obtaining the project requirements begin with the collection of black and yellow water from 26 4 households followed by their treatment. The waste-water is treated using the modified septic tank which has a baffled reactor installed in it. This septic tank is in anaerobic condition initially and so the dissolved oxygen (DO) level is very low.
In anaerobic tanks, most of the solid is retained and then further degraded by microbes. Oxygen is then provided to the system by means of diffused aeration. Following aeration, air is blown from bottom so that the system is enriched in oxygen. Until this stage, it is expected that most of the solid must have been degraded by the microbes in the baffled reactor. After the anaerobic unit, an aerobic unit is provided to further clean the water. A pressure pump in utilized in the next step in which sand acts as a filter so that the leftover solid particles will be filtered through sand. It starts working automatically once contents in the tank reach a certain volume. This pump will backwash the sand as well. This whole process from baffled reactor to the filtering of water is automated. Finally, the water is sent in for chlorination.
This simple septic tank is capable of recycling 2600 litres of water everyday. Recovery percentage lies between 80-90% and the whole setup costs less than 5 lakhs! Owing to the hours need to become environment friendly, the system is designed to run entirely on solar power.
On the whole, this anaerobic bio-digester is energy efficient as well as cost efficient. Residents of Medavakkam responded with positive reviews saying they were quite happy with the quality of water and were pleased to recycle and reuse the water, thus displaying their faith in this new technology. Back in campus, a modified septic tank with sensor, is in process of being installed in KV school. The sensors, one at the inlet and the other at the outlet will check the quality of water by measuring values for turbidity and dissolved oxygen (DO) levels. If the quality of water isn’t found to be up to the mark, it will be drained out to the soak pit for further treatment.
The Zero- Discharge Toilet
In association with Prof. K. Srinivas Reddy from the Mechanical Engineering Department, the idea of zero-discharge toilet emerged from Dr. Phillip’s group. Research scholar Krithika, an active member in this project, tells us about the usefulness and functionality of these kinds of sustainable development technologies in our society. Amidst the erratic power supply, lack of funds and skilled personnel, it is a challenge to look upon wastes from wastewater treatment plants as a resource even after putting it through rigorous treatment.
Composition-wise, black water (waste-water containing feces, urine) is very different from grey water (waste-water generated from shower,baths, washing) . Krithika adds, We can’t combine black water with grey water as black water has more pathogens and it is also rich in nutrients. Zero-Discharge toilet is a manifestation of sustainable treatment of black-water using renewable energy sources. The crucial challenge before the team was to find out means to use black water as fertilizers by extracting its nutritional value. The working principle of zero-discharge toilet consists of several steps showing below:
There are plenty of advantages in installing a zero-discharge toilet. First, it is very cost-efficient as there is no external electricity supply to it. Second, since it solely depends on the solar power for distillation, it can easily overcome the problem of inconsistent power supply. Third, the automated system eliminates the need for a centralized wastewater treatment plant and related transportation and maintenance costs.
The project kicked off with studying a lab-scale setup to properly understand and monitor the effectiveness of the methods devised to run the system. The pilot scale system comprised of:
- Data Logger-For online monitoring of ambient and instrument temperature.
- Pyranometer-For the measurement of Intensity of Solar radiation.
- Separator With Conveyor System-For separation of solid and liquid wastes.
- Inclined Photo Rector-For converting untreated urine into condensate.
- Solar Photodryer–For converting solids fecal matter into soil conditioner.
Synthetic urine and fecal matter had been used as samples for treatment. After separating the solid and the liquid from the waste, the liquid goes to the pump and then passes through the inclined solar photo-reactor unit. The inclined solar reactor gets more sunlight and the excess heat evaporates the water content in the urine and helps the untreated urine to condensate. Then, the treated fresh water is collected. The other part of the waste, namely the solid wastes (fecal matter) are slowly transported to the dryer using a screw conveyor. An inclined stepped photo-thermal dryer is used afterwards. After drying, synthetic bacteria is added to the dried fecal matter which can then be used as a potential fertilizer. The distillation unit was able to achieve almost 90% recovery of water from the liquid waste (urine).
On obtaining encouraging results from the pilot plant, the team finally decided to set-up the real-time zero-discharge toilet. The team has designed and built their very own zero-discharge toilet and it has been installed. The designed system is flexible, compact, stand alone with zero discharge. Moreover, it utilizes solar radiation as the energy source. near the Brahmaputra hostel in IIT Madras.
The field-scale system consists of similar parts used in pilot lab scale setup. The main components that have been used are shown below:
The sustainability and the efficiency of the project has been highly applauded and for which the team was felicitated with the prestigious J.C.BOSE-Patent Award.
The Future of Wastewater Management
“If we don’t plan for long-time solutions we’ll be having plenty of problems.” warns Prof. Ligy Phillip, at the end of our meeting. Though a lot of effort is involved, the awareness on water scarcity and recycling has not penetrated to the ground levels of human society. While the decentralized sanitation system had been embraced long back in the first world countries due to their geographical and demographic characteristics, in India we are far away from applying the concept of decentralization to our sanitation system and realizing its benefits.
Prof. Phillip suggests that the regulation surrounding waste and sewage treatment should be more stringent in order to see a positive change come through. This means accounting for every drop of water that forms septage, washing machines, bathrooms and looking for ways to recycle them and ensuring utilization to the fullest.
All things said, technology alone can’t combat water scarcity and sanitation problems. Rather, proper policy and most importantly our awareness regarding these issues should increase to counter the problems.It’s high time to address these issues and set up proper goals for future to eradicate these problems.
References:
[1] Link : http://www.un.org/en/sections/issuesdepth/water/
[2] Physical water scarcity region : More than 75% of river flows are withdrawn for agriculture, industry, and domestic purposes;
Economic water scarcity region : Water resources are abundant relative to water use, with less than 25% of water from rivers
withdrawn for human purposes, but malnutrition exists.
[3] Link : http://www.wssinfo.org/
