Technology

Water is life, essential for daily sustenance and healthy living. With plummeting groundwater levels, contamination of water sources and increasing consumption, challenges in the water sector have increased manifold. Safe, sustainable and affordable water in the face of growing water needs is a severe challenge. With fresh water supplies already hard pressed to meet growing demand, technology plays an important role in managing and using the limited available water in a cost effective and critical manner.

Water contamination occurs both due to human activities and natural processes. Depending upon the purpose for which the water is needed--municipal, industrial or agriculture--treatment is carried out. The technology used will depend upon the current water quality, future standards required and economics of the treatment method. Water treatment removes contaminants that may be biological, physical or chemical in nature. 

Various water treatment technologies are present that purify polluted water by removing undesirable chemicals or biological contaminants and making it fit for human consumption. Use based classification of surface waters in India has been laid down by the Central Pollution Control Board (CPCB). The details of the permissible and desirable limits of various parameters in drinking water as per Bureau of Indian Standards (BIS) standard specifications for potable water are also detailed in the IS 10500:1991

Water treatment plants use technologies to produce water that is safe both chemically and biologically, and that is appealing in terms of colour, odour and taste. The control point for water quality determination must be the consumer's tap and not the treatment facility, which means that the water quality must not be impaired during transmission, storage and distribution to the user. The treatment methods at the plant include aeration, coagulation and flocculation, sedimentation, filtration and disinfection.  Some of the prevalent water purification & treatment technologies are listed below.

  • Capacitive Deionization (CDI) is a technology where ions are removed from water by passing it through a spacer channel with porous electrodes on each side
  • Ozonation is a chemical water treatment technique based on the infusion of ozone into water
  • Ultraviolet technology uses Ultraviolet light, just like sunlight, to kill micro-organisms present in the water
  • Reverse Osmosis (RO) is a technology that removes a large majority of contaminants by pushing the water under pressure through a semi-permeable membrane
  • TERAFIL is a burnt red clay porous media used for filtration & treatment of raw water into clean drinking water, developed Council of Scientific & Industrial Research (CSIR), Bhubaneshwar 
  • OS- Community scale Arsenic Filter is an organic arsenic filter, developed by IIT Kharagpur
  • Filtration methods that may include rapid/ slow sand filters remove dirt, rust, silt, dust and other particulate matter from water
  • Solar water purification systems 

Water treatment technologies for safe, potable water in rural areas that includes Capacitive Deionization Technology (CDI) using carbon aerogel, solar operated groundwater treatment plants and electro chlorination are described in a booklet ‘Compendium of innovative technologies on rural drinking water & sanitation’ by the Ministry of Drinking Water and Sanitation. 

Domestic drinking water filtration methods vary depending upon the method of purification used, the degree of ‘purity’ required, and the type of contaminants in the water. No one technology will fulfil all criteria--there is no ‘silver bullet’ solution. Some of the more popular methods for Household Water Treatment & Safe Storage (HWTS) options includes boiling, SODIS (Solar disinfection), Chlorine Tablets, Liquid Chlorine (online, Biosand filters, Flocculent treatment, Ceramic candle, Filter combinations, Pureit filters, Ultra Violet (UV) filters, Reverse Osmosis (RO) and Ion Exchange (IEX).

For more on water purification systems, click here.

Domestic Greywater Recycling Water filtration technologies

Any used water, other than sewage from toilet basins that exit a house or apartment complex, is referred to as sullage or greywater. This is mostly made up of water used in bathrooms and kitchens, constituting the bulk--nearly 60%-70%--of the total volume of water used in a day. 

Before underground sewerage was introduced in most cities, water followed a cyclical route. Water was drawn from dug wells within the premises. Refuse water from the bathrooms and kitchen was let out into the garden while water from the closets reached septic tanks. The soil treated the greywater and sent it back into the ground, thereby closing the household water consumption-reuse loop.

Contrary to popular belief, greywater is largely free from pathogens. As it is mostly made up of easily degradable organic waste and chemicals from cleaning products, it can be purified and reused in-situ with minimal effort. In many homes and apartment complexes, sending this perfectly reusable resource out of the plot along with sewage common-sight. Greywater can be brought back into the water cycle by employing simple biological and mechanical filtration techniques.

There are two basic requirements apart from the necessary plumbing arrangements for treating domestic wastewater:

  1. Open soil space
  2. Water loving plants

Water from bathrooms and kitchens can be diverted through a dedicated pipeline into the plant bed set aside for the treatment process. Here, the nutrients present in the waste water are absorbed by water loving plants such as Canna or Cyperus while the soil bacteria polish off the organic waste from the water. 

  • Constructed wetlands – These wetlands are created to replicate the process of bio-filtration that occurs in a natural setting. Here, the water is purified using two media, the planted surface and the gravel bed underneath. 
  • Reed bed treatment plants – A smaller version of the constructed wetlands, reed beds are perfect for individual houses and smaller complexes.
  • Mechanical filtration – Mechanical systems such as sand filters and pebble flow systems can be used to help filter out waste from the water by separating the discernable solids from the liquid component. 
  • Lava filters – These pebble filters are a combination of both biological and mechanical systems where the stones act as support structures for microorganisms that help break down the waste. 

For more on the basics of rainwater harvesting and greywater recycling, refer Self reliance in water: A book by Indukanth Ragade.  

Sewage treatment--Municipal and Industrial

Waste water flowing out of urinals and toilet closets are referred to as ‘blackwater’ or sewage. Blackwater cannot be treated in the same way as greywater as the former contains a heavy pathogen load from the fecal matter suspended in it. Sewage from towns and cities flowing directly into water bodies is one of the major reasons for water pollution.

Municipal wastewater treatment plant, Yelahanka, Bangalore

While City Corporations are in charge of laying underground sewerage pipes to collect, channel and treat sewage, localities outside city limits have a greater responsibility of managing their own waste. Apartment complexes and townships mostly rely on small scale sewage treatment plants (STP) to treat their waste.

Wastewater can be treated either in the presence or absence of oxygen. While aerobic digestion involves the breakdown of waste by microorganisms in the presence of oxygen, anaerobic systems work in its absence. Various types of processes are used to treat both domestic and industrial waste water such as:

  • Activated Sludge Process where biological agents such as bacteria are used in the presence of air to oxidise the nutrients present in the sewage 
  • Sequencing Batch Reactors help equalize, aerate and sediment waste water in timed batches by mixing it with activated sludge and oxygen to reduce the organic load 
  • Membrane Bio Reactors provide a higher degree of organic and solid removal by combining the principles of both mechanical filtration and biological digestion to treat municipal waste 
  • Moving Bed Bioreactors are mainly used for aerating and treating high-strength wastewater where several floating polyethylene bio-films move in suspension provide surface area for the nutrient-digesting bacteria to grow 
  • Trickling filters are low-cost, aerobic systems made up of a fixed bed of gravel, rocks and moss over through sewage is passed to remove the nutrient material in the suspension 
  • Facultative aerated lagoons are shallow ponds where the sewage is allowed to with the atmospheric oxygen in the upper layers while the sludge settles down at the bottom 
  • Waste stabilisation ponds, categorized into three broad types – anaerobic, facultative and aeobic depending on the oxygen use intensity – help in reducing nutrient content and polishing waste water to re-use quality 
  • Up-flow anaerobic sludge blanket digestion treats wastewater in the absence of oxygen where the feed enters the tank through the bottom and flows upward as the bacteria present in the sludge digest organic the matter 

The CPCB publication on the status of sewage treatment in India throws light on the performance of sewage treatment plants across the country and the technologies currently being used in them. The status of waste water generation and treatment across the country is also available on the ENVIS Centre on hygiene, sanitation, sewage treatment systems and technology. 

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    Amita Bhaduriposted 4 days 13 hours agoread more
  • The Government of India has passed a draft notification to bar membrane based systems such as Reverse Osmosis (RO) to be used as domestic purifiers in cities where the tap water is safe according to the Bureau of Indian Standards (BIS) norms. This is to comply with an order of the National Green Tri...
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  • Karnataka allowed to implement Kalasa-Banduri project In a major relief to the Karnataka government, Centre has issued a gazette notification for the implementation of the Mahadayi water dispute tribunal’s August 2018 verdict. The notification allows the Karnataka government to go ahead with the ...
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  • Limca Book of Records recognises UP's Banda for water conservation efforts Uttar Pradesh’s Banda district has entered the Limca Book of Records for the construction of 2,605 contour trenches and holding 469 jal choupals (village water parliaments) in a single month. The efforts were made und...
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  • Maharashtra is the second largest sugar producing state in India, after Uttar Pradesh where as high as 1.6 million farmers cultivate sugarcane on 0.7 million hectares of land. The sugarcane industry provides direct employment to about 0.16 million workers while 1.5 million workers engage in sugarcan...
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  • Surrounded by vast expanses of water, the Kuttanad region in Alleppey district, Kerala faces severe drinking water scarcity due to infrastructure failure and civic body inaction. This picture-perfect expanse that lies at the heart of the backwaters experiences “frequent floods, waterlogging, conta...
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  • Northeast has 60 polluted river stretches: CPCB According to the latest State of India’s Environment report, there are 60 polluted river stretches based on biochemical oxygen demand in different northeastern states. The polluted river stretches in the northeastern states are Bharalu, Basistha,...
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  • World Bank to provide USD 450 million loan for Atal Bhujal Yojana The Centre and the World Bank have signed a USD 450 million loan agreement to support the Atal Bhujal Yojana that aims to arrest the country's depleting groundwater levels and strengthen groundwater institutions. The programme will b...
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  • It’s a dull reality that the state of water in the urban slum of Lalbagh near Azadpur in north Delhi was awful till a few years back. Hoards of people would queue up to get water from the public taps or the tankers along the road. Life was tough here and people got access to piped water supply onl...
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  • Arghyam has compiled a brief presentation which gives details of the permissible and desirable limits for various parameters in drinking water as per Bureau of Indian Standards (BIS) specifications for potable water (IS -10500: 2012). While the standards were first published in 1983, this ...
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  • Government allocates Rs 11,500 crore to Jal Jeevan Mission for 2020-21 In the budget 2020-21, the Finance Ministry has allocated Rs 11,500 crore to the Jal Jeevan Mission for the year for 2020-21. The funds will be utilised to identify and create comprehensive measures for 100 water-stressed dis...
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  • The use of reverse osmosis (RO) purifiers has become a contentious issue, mainly because of the amount of water that is wasted following its use. Last May, the National Green Tribunal (NGT) issued an order to ban RO purifiers in cases where the total dissolved solids in the water source were less th...
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Why women need to be trained and engaged in monitoring and surveillance of water quality at the community level in rural India?

Historically, water is a gendered burden, with women being the primary caregivers responsible for cooking, washing and cleaning chores in the house and in modern times in institutions (teachers, anganwadi and healthcare workers). Women have traditionally been associated with various water related tasks - be it collecting, fetching, or purifying water.

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While the government has passed a draft notification to bar use of Reverse Osmosis (RO) purifiers in cities, what does evidence on the ground tell us?

The Government of India has passed a draft notification to bar membrane based systems such as Reverse Osmosis (RO) to be used as domestic purifiers in cities where the tap water is safe according to the Bureau of Indian Standards (BIS) norms. This is to comply with an order of the National Green Tribunal (NGT) that proposed a ban on RO in the NCR region.

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Policy matters this week

Karnataka allowed to implement Kalasa-Banduri project

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News this week

Limca Book of Records recognises UP's Banda for water conservation efforts

Uttar Pradesh’s Banda district has entered the Limca Book of Records for the construction of 2,605 contour trenches and holding 469 jal choupals (village water parliaments) in a single month.

Topics

Sub-Categories

Regions

A report highlights the dangers for the millions of people who clean toilets, sewers and septic tanks the world over and calls for urgent action.

Many of the challenges sanitation workers face, stem from their lack of visibility in society, says a report ‘Health, Safety and Dignity of Sanitation Workers’ produced jointly by The World Bank, International Labour Organization (ILO), Wa

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Sub-Categories

Regions

Overworked, poorly paid and deprived of any rights, migrant cane cutters, especially women are most vulnerable and continue to suffer from a number of health and security risks.

Maharashtra is the second largest sugar producing state in India, after Uttar Pradesh where as high as 1.6 million farmers cultivate sugarcane on 0.7 million hectares of land. The sugarcane industry provides direct employment to about 0.16 million workers while 1.5 million workers engage in sugarcane harvesting and transport operations every year.

While Maharashtra boasts of having the largest cooperative sugar mills in India, private sugar mills are gaining prominence over cooperative mills over the last few years.

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Floods such as in 2018 could take the situation downhill causing severe drinking water crisis.

Surrounded by vast expanses of water, the Kuttanad region in Alleppey district, Kerala faces severe drinking water scarcity due to infrastructure failure and civic body inaction.

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Topics

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Regions

News this week

Northeast has 60 polluted river stretches: CPCB

According to the latest State of India’s Environment report, there are 60 polluted river stretches based on biochemical oxygen demand in different northeastern states.

Topics

Sub-Categories

Regions

Policy matters this week

World Bank to provide USD 450 million loan for Atal Bhujal Yojana

Topics

Sub-Categories

Regions

Women swipe clean drinking water through an automated dispensing unit at the Lalbagh slum.

It’s a dull reality that the state of water in the urban slum of Lalbagh near Azadpur in north Delhi was awful till a few years back. Hoards of people would queue up to get water from the public taps or the tankers along the road. Life was tough here and people got access to piped water supply only recently. Paying for clean water from private companies was unaffordable and people often depended on sources that were polluted and unsafe to drink. Women and children had to bear the burden of water collection and this cost them a lot in terms of time and energy.

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