Okay, welcome back, last lecture we discussed about wastewater management scenario in India,
and what all are the treatment options.
Today we'll talk about wastewater recycling, a sustainable option for water management,
we'll see some case studies.
So we all know that water is a precious and scarce resource, and in the previous lectures
we have seen that only a small fraction is fresh water less than 3 percentage and India
is the wettest country in the world but rainfall is highly uneven with time and space, extremely
low rainfall in Rajasthan and high in North-East, on an average there are only 40 rainy days.
And to sustain our growing demand for agriculture and other uses we abstract the water from
every possible sources, out of 4000 BCM rainfall received, about 600 BCM is put to use so far,
remaining is just running off to the sea.
Water resources are over-exploited resulting in major water quality problems.
So this slide I have already explained to you in the last lecture, okay, availability
and type of toilets and okay we are majoring of India is still depending upon septic tanks
and or decentralized than onsite wastewater treatment systems, or mostly onsite wastewater
management systems.
But okay there are many decentralized wastewater treatment systems also, so we will see what
is the present status of decentralized wastewater treatment systems in India, I already explained
to you what is the decentralized systems more than 8000 plants are existing, okay, this
is a secondary information we have collected and technologies employed in decentralized
system,
okay, when we talk about centralized wastewater treatment system or decentralized wastewater
treatment system the technologies can be the same, okay, here we can see that India has
all this type of wastewater treatment system, vortex, and anaerobic filter, Dewat systems,
decentralized wastewater treatment systems, membrane bioreactors, extend aeration, ASP,
anaerobic upflow sludge blanket reactor, onsite package systems, contact aeration, okay, MBBR,
EA package, soil biotechnology, okay waste stabilization, ponds, sequential batch reactors,
RBC, okay, all this technologies are being employed in, okay decentralized wastewater
treatment systems also.
So if we look into how it is distributed, okay, this shows you, so this is North Eastern
region I have put, all the technologies here and the number of plants, North Eastern states,
yeah, we have decentralized treatment systems, but the number is okay in the range of okay
10 to 15, different technologies okay be around 10 to 15 plants in different places, Western
region you can see that the Y axis become 40 to 100, okay that means the number of treatment
plants in Western region is much more, and Eastern region again it is similar to Northern
region, the plants are relatively less, okay, around 5 to 10 plants of east technologies
existing, and if you see the Southern region it is very high, okay, the number is going
40, 50 and some plants are going up to 160 to 200 that means lot of decentralized plants
are available in India.
So if you see the treatment efficiency, okay, you can see that irrespective of the technology,
okay, some plants are working very well, and some plants are not working that good, okay,
this is for COD removal, this is BOD removal and this is the COD removal, okay you can
see that okay, some plants are working good and some plants are not working good.
Similarly I have the TSS value and fecal coliform number, what I'm trying to tell is different
technologies are available, okay, most of the technologies are able to meet the requirement
or wastewater quality discharge standards, most of this plants are able to meet if it
is operated on maintained properly.
So challenges to be tackled through policy, what extend one need to recycle, this we have
to see, because when we talk about the recycling many people are having psychological inhibition,
how can I use my wastewater for other purposes, we are forgetting that we are doing that one
unknowingly on day to day basis, I explained earlier the river water it is receiving lot
of untreated wastewater from other cities and we are doing that one, so okay this is
one challenge, quality, okay what quality we have to treat it is based upon the beneficial
use, quantity not affecting the functioning of existing infrastructure, because if you
recycle too much of a wastewater the flow in the sewers will be getting affected that
also we have to look into.
Land availability that is another problem, existing regulations regarding the distance
of STP's from habitations, and infrastructural development rules all those things we have
to look into.
Then social acceptance that is another problem, awareness creation and social engineering
is essential to tackle the waste management issues.
Then monitoring and enforcement, okay, we have to have, because what is happening is
people are putting last number of plants and if it is not monitoring what will happen,
all the untreated water will be getting into the ground and ultimately it will be contaminating
the groundwater and surface water, so we have to have proper monitoring and enforcement
that means okay when you have a wastewater treatment plant, plan approval, third party
monitoring, consent to renewal in frequent intervals, smart monitoring and appropriate
actions, all those things can be thought about.
Then economics of the plans we have to look into, if the plan is very costly nobody is
going to construct the plans, we can look into prefabricated modules, economics of scales,
pricing of virgin and treated water, because if you put a very high price for the pure
or virgin water then people will have a tendency to use the treated water, tax rebates, rating
of buildings etcetera are other benefits one can give if people are going for the wastewater
recycling.
So I'll talk about how a campus can be, okay, sustainable okay can manage the wastewater
in a sustainable way, so I'm giving the example of Indian Institute of Technology, Madras,
Chennai, so this also basic information, the total
population is around 15,000, projected population is okay for the next 5 years, 10 years around
20,000, present water consumption is around 3.2 million liters per day, projected is around
4 million liters per day, wastewater generated at this moment is around 2.8 million liters
per day.
So IIT Madras has constructed a 4 million liter wastewater treatment plant using the
technologies sequential batch reactor and what the institute has done is after creating
the wastewater treatment plan they have put up a tertiary treatment unit of ultra-filtration
and disinfection unit okay with Ozonation, so the treated water quality is very good
and the sludge whatever is generated is, okay, centrifuges and try okay to use it as a manure,
so this is the existing wastewater treatment plant and you can see
that this is the treated wastewater, so here we have put different, okay, water samples
one is secondary treated water, tertiary treated water, tap water, RO water etcetera, so it
is very hard to, okay, find out which is the treated wastewater and which is the tap water,
what I'm trying to tell is if you put a properly descend wastewater treatment plant and operate
it properly you can get very, very good quality water.
So after that one what we are doing is this water, the entire campus is having dual pipeline
system, so this water is, okay the treated wastewater is being pumped across that campus
and is being used for all the toilet flushing, gardening, and as a cooling water for all
the centralized air-conditioning unit, and whatever the excess water is coming okay we
are, okay, using it to augment the water in this lake, and you can see that we are getting
lot of birds and fishes and all the things in this lake, not only that one because of
this one the groundwater to some extent the groundwater recharging is taking place.
So we are not only doing that one, so we have a lake, this lake is our rainwater, storage
rainwater harvesting system, so all that rainwater drains, drainage system are directed to this
lake so whatever the rain comes in the campus or rainwater comes in the campus everything
is collected in this lake and we have a small treatment unit and this treatment unit is
augmenting the water supply, okay, whatever we are getting from the Chennai, metropolitan
CMWSSB, okay, so here what treatment we are doing?
We are having a coagulation, flocculation, filtration and chlorination, the conventional
treatment we are doing and we are constantly monitoring the quality and all the things.
So what I'm trying to tell is by doing this type of a system, so within one year we could,
the institute could save around more than 1 crore rupees on water bill itself, not only
that one we are supplying water to our neighboring campus and from there also we are getting
okay around 7, okay, in one year we are getting around 8 lakh rupees, okay we are selling
the water for around 18 rupees per meter cube.
Now what I'm trying to tell is if we have the wind, okay we'll be able to reduce our
water consumption by 50 percentage by properly treating the wastewater and recycling in,
by doing this one we are reducing the pollution problem and we are reducing the virgin water
extraction from the sources.
And okay if you want to look in to, okay, which one will be economical because if you
talk about a very sophisticated wastewater treatment system, if it is a very small plant
the unit cost maybe very, very high, okay, so this is the unit cost for SBR wastewater
treatment system, and here I have given the comparison of different
treatment technologies and their cost and all the things, okay, whenever you have time
you can look into that one, so that is one approach.
Another thing is whether we will be able to achieve zero liquid discharge in a household?
Yes it can be, okay, but the system should be reliable and cost effective, and okay whatever
we are providing there should be social acceptance, okay, it should be sustainable, less demand
on resources, and as far as possible a close loop should be maintained, so okay students
have done many projects in this area, I'm going to discuss a few of them, okay, so this
is what we are trying to tell you, okay, a person will be consuming
around 135 liters per day water for various purposes like drinking, cooking, personal
washing, cloth washing, homework, car cleaning, lawn, gardening, toilet flushing, so when
we talk about this one we need very good quality water for drinking and cooking and dish washing,
when it comes to okay bathing and cloth washing yeah good quality water should be there, but
home, car cleaning, and lawn, and gardening moderate quality, and when it comes to toilet
flushing okay we can use any quality water because we are just pushing the material outside
that toilet, that's what we are using this flushing water.
So if you look into this one, so what we can do is use only flush water for drinking and
cooking purpose, this personal washing or bathing water and cloth washing water we can
recycle it there itself and whatever the cooking and drinking water waste coming okay we can
use it for home and car cleaning or lawn and gardening, and kitchen waste and whatever
the other left out waste coming you treat and use it for toilet flushing, so by doing
this one we will be able to okay reduce the fresh water requirements significantly.
So this is some work studies we have conducted recycling of water within the washing machine,
okay, because you know that each time when we washed the cloth around 45 liters of water
for household, a small household, around 45 liters of water is being used for a 6 KG washing
machine, and we will be using it for 3 cycles, so 45, around 135 liters of water is being
used, so if you can clean it and recycle it we can save a lot of water, so that's what
we were looking into, so we looked into various treatment technologies
and all the things, okay, and we have come up with a very simple process, some coagulation,
flocculation and filtration, and the important thing is, okay between the washes we'll be
getting only 12 minutes time, within that time you have to
treat the water, so we have develop the system and you can see that this is the treated water,
the treated water is almost equivalent to the tough water, and you can see the quality
here, okay, the treated water is meeting, okay you can see
the organic carbon very little, okay total coliforms came down to the BDL, and your turbidities
around 1.62 that means okay you are getting very good treated quality, okay using this
method and you can develop, okay, better insemination systems and or so that this water can be pump
back to the washing machine and okay thus water can be saved, okay, so we have already
filed packing for this technology.
And another thing is solar power water recycling toilets ensuring hygiene and safety, so here
what are doing is, from the schools and all, for example in water stressed areas many schools
will not be having enough water to flush the toilets and also it is creating a major problem
for the girls students and, the students in general, so we were looking into a system
rather we can develop a wastewater treatment system, okay, which doesn't need any electricity
from the grid, and which doesn't need any, which doesn't need much operation and maintenance
and the quality have to be assured or quality has to be checked on daily basis, so that's
what we have done and you know that the school wastewater is very difficult to treat compare
to domestic wastewater, because the organic or carbon content is very less, and your nitrogen
content is very high, so what we have done is, okay, we developed a treatment system,
this is the modified septic tank, then we have a small aerobic system, then you have
a filter, it can be a ultra-filter unit or a sand filter depending upon what quality
you need.
And entire thing is powered by solar system, but you know that sunlight is available only
during the day time, so we have designed our aerobic system in such a way that whenever
the solar power is there the system will be working and it will be meeting the required
standard, so that is the importance here, and what we have done is we have also developed
some sensor which can, okay, cheap, or inexpensive sensor which can be fixed online to the treated
water line and we can check the quality, if the quality is meeting the water will be going
to the storage tank, overhead tank, if the water quality is not meeting we have the drainage
field it will be flushed to the drainage field, so what is happening here, the maintenance
is very, very minimal and power cuts are not going to affect the treatment system and the
quality, quality is assured okay so that the students are not under risk, so this type
of a system, okay definitely will be helpful for schools, okay, what is happening, all
the wastewater we can treat it, and recycle for flushing, purpose of flushing and gardening
purpose so that the water curiosity will not be affecting the toilet usage,
so this is the sensor, the sensor we have developed is based upon color, turbidity,
and oxidation reduction potential so that those parameter indirectly tell you whether
your treatment system is working effectively and whether it is meeting the required standard,
so this is the sensor we have developed.
Okay we have done extensive large studies and you can see that, okay a combination of
this modified septic tank and the submerge and aerobic biofilm, okay altogether we are
getting around 96.32 percentage of COD removal, and
more than 95 percentage of ammonia nitrogen and total nitrogen removal, okay, so this
system is performing very well and we have already installed the system in two schools,
and the cost for 5 meter cube wastewater treatment is coming
around 8 lakh rupees, okay, but this cost can be reduced significantly if you go for
multiple units at a time, so what I am trying to tell is there are very simple technologies
which can do wonders and the wastewater can be treated effectively and you can reuse the
treated water.
So and the same system can be use for residential complexes, there the treatment is much easier
because you have enough carbon and nitrogen, so we have also put up similar type of plants
in some housing complexes, okay, so this is the treatment system, okay and you can see
that the wastewater, okay, the quality is improving
very significantly well and this is the raw water and the treated wastewater, okay, it
is very good quality.
And another example I'm going to explain is design and development of solar thermal energy
system for domestic sewage treatment, especially black water, okay, these systems are suitable
for the areas where you don't have much water supply and much power supply especially for,
okay remote areas or tourist places where you don't have access to such places, so here
the system is very simple, what we are doing is from the toilet whatever is coming you
separate the solid and liquid, okay, and solid you try using a solar dryer and the liquid
what you do you go for vacuum distillation using solar power so you'll be getting very
good quality, okay, distilled water and you'll be getting solids free of all the pathogens
which is very rich in nutrients and organics which can be used as a fertilizer, so initially
we have done the laboratory studies and all the things, okay, and we could see that, okay
all the pathogens are getting killed in the liquid as well
as the solid, okay, so this is the thing and when you do the distillation you can see that
this is the raw water you can see the color and this is the condensate it is as appear
as distilled water, okay, and you get around 10 to 15 percentage reject,
what we do is this reject you mix with the solid and try it, so that the nutrient content
of the solid will be very, very high and the solid is free from all the pathogens and other
things, okay, so this are our pilot scale systems, okay.
Okay we could get very good efficiency, okay, and this is the dried solid which can be used
as the manure and we have already installed a unit, okay, for toilet unit with the trier
and other things it is working very well, so what I'm
trying to tell is okay we can think of different options, okay which will be recovering all
the resources present in the wastewater, okay, here we have two advantages, one is we are
protecting the environment from the pollution that means no residual pollution is getting
into the environment and we are recovering all the resources and we are reusing, so these
are the sustainable ways of managing wastewater.
I will also show another very simple method of treating the grey water, we can use constructed
wetland and constructed wetlands are different types available, horizontal flow, vertical
flow, hybrid, or the grow system that means okay which can be kept in the roof top or
even in your front yard or backyard, okay, different types of wastewater and we also
looked into how the surfactant and all are getting reboot because when we talk about
the grey water, grey water is nothing but the water coming from bathrooms,
washing machines, and washbasins, so it will be having lot of surfactant condense and all,
so we were looking into the fate of this compounds etcetera in the constructed wetland, whether
the water is safe or reuse that also purpose, so this is the constructed wetland, okay around
10 meter long, 2.5 meter each, okay, so we have put it in
the hostel and you can see that okay the plants are growing very well, okay, so what you have
to do is okay have a settling tanks so that if you have any settleable solids it will
be settling then allow the water to pass through the constructed
wetland, so all the pollutants will be getting removed by the combined action of physical
processes, chemical processes and biological processes and you will be getting clear water,
this water can be okay can be used for flushing purposes, gardening purposes and all, so this
is an example of grow system, okay, this looks like
a garden and the water is subsurface flow so you'll not be having any mosquito menace
or anything, so the water indorse here and it flows like this in a pluck flow manner
and you will be getting the treated water.
So you can put any type of plants, flowering plants so it will be looking as a, looking
like a garden, so you can put it in the front yard or in the roof and you will be getting
all your grey water treated properly, so I am showing some example okay you have a raw
grey water and we are treating and using the horizontal flow system, vertical flow system
and hybrid flow system you can see that how the concentrations are getting reduce, okay,
this is the chemical oxygen demand it is getting reduced to okay, very less 8 milligrams and
this is the BOD, TOC and even the surfactants are getting reduced to very, very low level.
What I am trying to tell is, okay there are many, many technologies some are very sustainable
and inexpensive for the management of wastewater, we can take them properly, we can reuse them
for various purposes without much cost and effort, so you can see the removal efficiencies
okay all the wastewater, quality parameters I have put it here and we are getting the
efficiency more than 90 percentage, 90, 95 percentage in most of the cases, okay.
And we also looked into the whether the plants whatever we are putting there, okay for example
I'm putting some fodder grass there, whether this fodder grass can be used as a fodder,
okay, whether it is having any health impact on the cows or cattles, okay, so we have looked
into how much is the surfactants and all getting accumulated in the plant, and we could see
that some amount is getting accumulated but it is not up to that toxic level so most of
the time it will not be a problem.
So in summary for the sustainable wastewater management first thing we have to do is waste
is not a problem, it is a resource, so once we realize that one half of our problem is
or majority of our problem is solved because the moment people realize that the wastewater
is a reliable source of water supply okay people will be in roasted to collect the wastewater
and treat it, so that is the first thing.
Second important point is practice, reduce, recycle and reuse option, wherever you get
lot of water don't try to use it as much, use as much as possible, try to reduce the
use, recycle and reuse the water because the resources are highly limited, protect the
natural resources and reuse the wastewater, because unless we manage our wastewater properly
it is very difficult to protect our surface and groundwater sources, so okay manage our
wastewater properly so that the natural resources are protected.
And if you reuse the wastewater you can significantly reduce the fresh water use, okay, it can be
reduced to 40 percentage of something like that okay because majority of our use can
be met by the treated wastewater, then proper operation and maintenance of the plants are
essential because many times what happens people will be putting up the wastewater treatment
plant with all the enthusiasm but when it comes to operation and maintenance they won't
be doing it, okay, if you are not operating and maintaining the plant properly, if the
plant will not work and it will lead to much more problem, so if you want to, okay, however
proper wastewater management we have to go for a wholesome approach to waste management,
okay, that means if you are talking about a city you may have to think about centralized,
decentralized plan, onsite systems as a whole and city sanitation plan etcetera are very,
very important in this aspect.
Thank you very much.