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Water Recycling and Reuse for Domestic and Industrial Sectors
Ajay Jindal, Chief Manager, Water Technologies, Larsen & Toubro Limited and Shama Kamat, Water Executive, Engg.& Const. Division Larsen & Toubro Limited Water is a crucial resource and affects different aspects of human life - food, energy, transportation, business, nature, leisure, identity, culture and social norms amongst other things. Water availability plays a very important role in our social and economic development. India has 16 per cent of global population, but only has four per cent of the global water resources. Water scarcity has become a major concern, owing to the pressures exerted on the water sources; climatic changes would further intensify this crisis. Managing ever-increasing water demand from the rapidly rising numbers of users in multiple sectors is perhaps the single greatest development challenge the international community is facing in the 21st century.
The major Indian sectors consuming water are industries, agriculture and the domestic sector. Out of the total water used in India, about 87 per cent is consumed by agriculture, eight per cent by industries and five per cent for domestic purposes.
Although industries consume only eight per cent of water, they are the worst affected during water crisis as they are given the last preference by the National Water Policy. Apart from being a crucial raw material, water plays a significant role in generation of energy through various sources, the two primary factors for survival and growth of the industries. Therefore, the unavailability of water results in breakdown of production and is a major risk.
Municipalities, on the contrary, are facing problems in meeting the demands of sprawling cities. Water supply, distribution and wastewater management are some of the most important issues faced by municipalities. The growing divide between cities and rural areas further pressurises the municipality to be self- sufficient. Issues like funding for the projects and cost recovery cause hurdles to development projects.
Centralised systems of wastewater treatment that have been implemented by various public authorities, have failed to ensure equal distribution of water. In addition, a number of technical and social issues associated with large projects hamper their effectivity. Decentralised systems of wastewater treatment seem promising in fulfilling the water demand in rural as well as urban areas.
However, water management should not be restricted to water treatment, but should also focus on recycling of water. Water recycling is being practiced by various sectors in countries across the world, and to some extent in India, particularly in the industrial sector. However, we have to go a long way in the recycling and reuse of our municipal wastewaters. A number of policies and norms are being introduced by regulatory agencies to encourage water recycling. This article aims to address the issue of water recycling in domestic and industrial sectors.

Status of India's Water Resources
India houses 16 per cent of the world's population, 2.5 per cent of the land mass and four per cent of the water resources. A number of areas are already affected by water crisis, including the most populated and economically productive parts of the country. Estimates reveal that by 2020, India’s demand for water will exceed all sources of supply.
At the same time, 70 per cent of India’s irrigation needs and 80 per cent of its domestic water supplies come from groundwater—in the past, a successful practice—but that has lowered groundwater tables and depleted aquifers. It is no longer sustainable. The picture is further muddied by unclear rules governing the allocation of water rights of the country’s interstate rivers, which drain around 90 per cent of India’s territory.
The water situation in India is worsening day by day. Rapidly exploding population, aspirational GDP growth, lack of technological knowledge and willingness are all responsible for this alarming situation. The dearth of water is due to two reasons; one being the limited availability of fresh water sources and the other being pollution of the existing sources, which further shrinks the sources available. Hence, India faces both quantity as well as quality issues pertaining to water. About 30 per cent of the population in India receives less than the basic service level (40 lit/capita/day) of water.
Based on water availability, India is ranked 132 out of 180 nations, whereas water quality-wise India is ranked 122 out of 130 nations. Further, about 80 per cent of all water sources are contaminated with pathogenic micro-organisms whereas, about 30 per cent of the total water sources are contaminated by heavy metals.

India's Water Requirement
National water use of a particular country is closely linked to its economy, as water is an essential component in agriculture as well as its industrial growth. Figure 1 shows the water use pattern in high-income (developed) countries vis-a-vis water use pattern in low income (developing) countries.


In India, about 87 per cent of the water is consumed for agriculture, followed by the industrial sector, which consumes about eight per cent. The domestic sector accounts for around five per cent of the total water consumption. According to the National Water Policy (2002) of the Government of India, water is to be allocated according to the following priority list:
1. Drinking water
2. Irrigation
3. Hydro-power
4. Ecology
5. Agro - industries and nonagricultural industries
6. Navigation and other uses

Domestic Water Usage
Municipalities are facing problems in meeting the increasing demands of sprawling cities. Water supply, distribution and wastewater management are some of the most important issues faced by municipalities. Growing divide between cities and rural further presurises the municipality to be self-sufficient. Issues like funding for the projects and cost recovery cause hurdles to development projects.

According to Central Public Health and Environmental Engineering Organisation, Ministry of Urban Development, Government of India (CPHEEO), standard per capita water requirement is presented in Table 1. Water supply and distribution authorities are required to design the system as per the norms given in the table recommended per capita water supply levels for designing schemes listed in table 2 and table 3 describes the amount of water that needs to be supplied for institutions. Figure 2 shows typical usage of water in the office building.

Water Consumption - What is required?
Our water needs can be summed up as following:
• Economical and optimal use
• Prevention of wastage
• Prevention of leakage
• Multiple Usage (reuse and recycling)

Water conservation in domestic and commercial buildings:
• Take shorter showers and use a low-flow shower head
• Run washers and dishwashers when full
• Never leave water running
• Waterless urinals
• Mulch trees and plants to retain moisture, prevent evaporation
• Use effective sprinkler heads, or better yet, use drip irrigation
• Use native plants and trees
• Harvest rainwater and use wise watering techniques
• Do not over water
• Be aware of water leaks and fix them

Salient water features in green buildings:
• Zero water discharge
• 100 % wastewater recycling
• Rain water harvesting
• Water efficient landscaping
• High efficient water fittings
• Water efficiency in A/C systems
• Innovative waste water technology
• Reduction of potable water use

Rainwater harvesting (RWH)
Rainwater Harvesting (RWH) is the practice of collecting, storing and distributing rainwater to use it as an alternative source of water. Rainwater can be collected through roof tops and paved or unpaved surface runoffs. The harvested water can then be filtered and stored either in tanks and reused, or recharged into the ground artificially. Main advantages of RWH are that this resource is absolutely free and has very low contaminant level. Because of this, it has superior taste, has neutral pH value, which makes it soft and free from sodium. Harvested water is secure and an on-site emergency resource of water. Additional advantages include ground water recharge, reduction in storm water run-off and LEED points advantage.

Recycling of Grey Water
Grey water is the domestic wastewater from bathrooms (such as basins, showers and baths), laundry fixtures (such as clothes washing machines and laundry troughs) and kitchen facilities (such as sinks and dishwashing machines). With minimum treatment, grey water can be recovered and used for applications such as toilet flushing and gardening. Grey water should not contain neither human waste, nor industrial waste.

Recycling of Black Water
Black water refers to wastewater that contains human waste. Black water is collected through toilets and urinals. This wastewater can be used for non-drinking purposes, once properly treated and disinfected. This recycled water can be used for gardening and toilet flushing through a dual pipe network.


Industrial Water Use
Industrial water use is closely linked to the economy of a country. As GDP increases, so will the industrial water consumption. The industrial water consumption in India is further expected to increase owing to the development of the economy (Figure 3). Although, industries consume only eight per cent of water, they are the worst affected due to water crisis as they are given the last preference by the National Water Policy. Apart from being a crucial raw material, water plays a significant role in generation of energy through various sources; the two primary factors for survival and growth of the industries. Therefore, the unavailability of water results in breakdown of production and is a major risk. Figure 4 provides the break-up of water consumed by various industrial sub-sectors. Thermal power plants consume around 88 per cent of freshwater, mostly for cooling purposes. A coal-based power plant consumes about 120-170 m3 of water/day/ MW of electricity produced. Thus, water requirements of 500 MW power plant is equal to total water requirement of city of about 6 lacs population. Specific water consumption by various industries is depicted in Table 3.


On comparing an average Indian industry with the best global industry, it is seen that the Indian industry is far more water intensive than its global counterpart. Higher water consumption in Indian industries is due to the sheer scale of inefficiency and waste in the industrial system, lack of proper information, dearth of pricesensitive and predictive water management information and the lack of a proactive approach.



Reclamation of Water
In order to mitigate the problems of water scarcity, an intergrated approach is required, which focusses both on water conservation and on wastewater recycling. Water conservation helps to reduce water wastage at the source, whereas water recycling helps to further reclaim water. In this approach, wastewater is considered as a source of raw water. Reclaimed water is much cheaper, in terms of capital as well as operating cost, when compared with the price of water in the long run, especially for industries where the cost of water is higher; typically 40-70 per 1,000 litres.

Need for Integrated Water Resources Management
The traditional basis for designing and operating infrastructure no longer holds good with climate change. It cannot be assumed that the future hydrological regime will be the same as that of the past. Climate change challenges existing water resources management practices by adding uncertainty. The key challenge is to incorporate uncertainty into water resources planning and management. Integrated water resources management is an increasingly used means of reconciling different and changing water uses and demands, and it appears to offer greater flexibility than conventional water resources management.

Water professionals are more familiar with working on the supply-side options. However, demand-side options are also increasingly becoming important. Conventionally, water resource professionals assume that the future resource base will be the same as that of the past and therefore, they are led to believe indices that are based on past data will apply in the future as well. However, under the climate change scenario, there are two issues: assessing alternatives in the face of uncertainty and making decisions on the basis of this assessment. Adopting integrated water resources management will go a long way toward increasing the ability of water managers to adapt to climate change.

Indian Industry and Water
At present the Indian industry is not getting the required quality and quantity of water. Currently, the Indian industry uses only about eight per cent of our national water. In developed countries the per cent use of industrial water is much more than the use of agriculture water. However, the water share of the Indian industry will be growing along with the growing GDP, thus fuelling the growth of the industrial water segment. According to a recent government assessment, the water requirement for industrial use will increase from the current 30 billion KL to 120 billion KL by 2025. Whenever there is a competition for water between different stakeholders, the industry will be at loss as agriculture and civil society is more likely to get preference. The Indian industry has to look for the maximum water recycling and other sources of the raw water, like wastewater and desalination of sea water and brackish water.

Water Recycling in Indian Industries
Indian Industry has realised that in most cases, cost of the recovered water is less than the cost of the fresh water from other sources. Chennai Petroleum Corporation Limited, Chennai (CPCL), is the leading example of water recycling with respect to magnitude and end use application. CPCL has 2.5 MIGD (475 KL/hr) reclamation of untreated city sewage plant through tertiary treatment and reverse osmosis. CPCL is executing an additional 2.5 MIGD (475 KL/ hr) city sewage reclamation plant. as well as a 5.8 MIGD sea water desalination plant. CPCL is the first company in India to go for a reverse osmosis rejects recovery plant of 80 KL/hr.

Other good examples of water recycling in the industry come from MFL, Chennai and RCF, Mumbai. MFL has total water requirements of 3.5 MIGD. MFL meets 2.5 MIGD of its water requirement through the treatment of municipal sewage. RCF has a municipal sewage recycling plant of about 24 MLD. This trend of recycling water in the industry is strengthening day by day. Most of the industrial effluent treatment plants are being set up with recycling facilities. As the water recycling plants are coupled with financial returns, the attitude of the industries is also changing fast. Initially the industry was not so keen on taking proper care of the effluent treatment plants, hich were mostly used for discharging the treated effluent purposes only.

Water Desalination
Desalination of water, including sea water and brackish water desalination is becoming a viable option not only for the Indian industry but also for potable use. Chennai Minjur sea water desalination plant represents the first major desalination project for municipal water use. This is a 25-years BOT contract for a 100,000 m³/d desalination plant to serve Chennai in Tamil Nadu. This plant opens the way for further large scale desalination projects in a country badly in need of sustainable water sources. For many Indian industries, sea water and brackish water desalination has become a viable option. For a large scale sea water desalination plant, the cost of product water is less than 4 paisa per litre. A number of Indian industries have already gone for the sea water desalination based on thermal or membrane based processes. Reliance Refinery is a major example. It already has five units of thermal sea water desalination and another four unit are under execution. Once the new units are installed, the refinery will operate nine desalination units, producing a total capacity of approximately 160 MLD. BARC has a 1,800 KL per day Nuclear Desalination Demonstration Project (NDDP) at Kalpakkam, using reverse osmosis technology. Another 4,500 KL per day plant is under construction at Kalpakkam on MSF water purification technology.

Summary
India is already an almost water stressed country. Water scarcity problem can be mitigated using an integrated approach, aimed at reducing wastewater generation and recycling the wastewater. Water conservation, rainwater harvesting and water recycling play an important role. These measures can be adopted at the municipality, community as well as at industrial levels. Water is the limiting factor for sustainable development and industrialisation. Water conservation and recycled water is cheaper than fresh water. Hence, water recycling is not a bottleneck but is a good business decision in the long run.