Sustainable Water Use

  

There is always a question of “Are we using water sustainably?” We may answer “Yes” to this question if less water is withdrawn than nature itself is capable of replenishing. The aim is to maintain sustainable levels of water resources, an important water shortage indicator. If countries use water much faster than it is replenished, resources begin to decline. This is precisely the situation that is beginning to arise in some countries where water stress and water shortage are becoming a reality due to increases in population and, consequently, in agricultural and industrial activity. Water demand and water supply are two terminologies related to the question we asked, where the former means the amount of water required for meeting specific water use purposes in given period of time, while the later means the amount of water to be delivered to the users in the same period of time usually through water withdrawal from natural sources. Water resource development is a topic related to the adjustment of water supply capacity (direction of supply enlargement), while water use to be discussed here is a topic related to the adjustment of water demand (direction of demand reduction). The objectives all together are to maintain a balance between water demand and water supply. Within the scope of centralized water supply to urban and industrial regions, the topic of sustainable water use usually covers water saving, reduction of industrial water use, and reduction of urban water use. 

Water Saving

Water saving it to reduce our water footprint. A water footprint is an indicator that looks at both the direct and indirect water use of an individual, business, community, city or country. The Water Footprint Network has provided tools to help us to calculate the water footprints for an individual person, a process, a product’s entire value chain and so on (https://waterfootprint.org/en/). Direct water use refers to the water we see coming out of the tap: the fresh water we use each day for drinking, cooking, showering, washing dishes and clothes, and gardening etc., while indirect water use refers to the water that is used to manufacture the goods that we consume or produce, and the services that we use, as well as all of the water that is made unusable by pollution or wasted by non-use. That includes all of the water used to grow the food that we eat, to produce the things we use in daily life – clothes, books and furniture – and the water needed to produce the energy we use. 

Direct Water Saving is to reduce our direct water footprint by various means such as turning off the tap while brushing teeth, using water-saving toilets, installing a water-saving shower head, taking shorter showers, only washing clothes when necessary, fixing household leaks, using less water in the garden and when cleaning, and so on.
Indirect Water Saving is to reduce our indirect water footprint by a number of different approaches. For example, the food we eat makes up a huge part of our personal water footprints, and implementing some of these changes could have knock-on benefits for our health too. We may try to practice eating less meat, switching coffee for tea, cutting down on sugar, eating less processed food, and consuming more local produce. All these can significantly reduce our indirect water footprint. Of course, for people to be able to make informed decisions about which options to choose, businesses need to be transparent about their processes, and governments more forward-thinking when it comes to regulation.
Business (Industry) Water Saving  can also be achieved by implementing a series of feasible actions such as reducing the flow of water, modifying the equipment or installing water saving devices, replacing existing equipment with more water-efficient equipment, and changing to a waterless process.

Reduction of Industrial Water Use

Probably every manufactured product uses water during some part of the production process. Industrial water use includes water used for such purposes as fabricating, processing, washing, diluting, cooling, or transporting a product; incorporating water into a product; or for sanitation needs within the manufacturing facility. Some industries that use large amounts of water produce such commodities as food, paper, chemicals, refined petroleum, or primary metals. The reduction of industrial water use is important for many regions and usually include the following measures.

Cleaner Production is a preventive, company-specific environmental protection initiative. Cleaner production processes utilize the raw materials more efficiently and lower the water and energy consumption. The production becomes more profitable and the environmental impact is reduced. By carefully analyzing the process and identifying the flow of materials, water usage and energy consumption improvements can be identified, quantified and implemented. Improvements which quickly are reflected on the bottom-line figures. Pay-back times typically range from a couple of months to a few years. A reduction of 25-50% of the water consumption is quite normal in water intensive productions when cleaner production processes are applied.
Industrial Water Recycling is the process by which wastewater produced from one source is treated to be reused in the same process or recycled for another. Opportunities for water recycling in an industrial plant may include general wastewater recycling, cooling tower blowdown, boiler blowdown, and once through cooling water. Various methods for recycling industrial water are available, depending on water quality requirements, space constraints, and budgetary considerations. Benefits can include the reduction of freshwater costs, wastewater flows, and the size of water footprint. Operational efficiency and sustainability can also be increased along with improved production capacity due to the increase in available clean water.
Sequential or Cascade Industrial Water Use is a special way of water recycling or water reuse where the used-water from one process is used directly in another process. This can be easily realized when the water quality has almost not deteriorated after the first process and still met the quality requirement for the second one. Multi-step water use may also made possible. 

Reduction of Urban Water Use

Urban water use usually includes household domestic use, municipal and commercial use, and environmental use. Although the quality requirement for different purposes of water use may differ from each other, the conventional manner is to supply water with the same quality which meets the requirement for potable use to the whole city for all purposes of water use. Therefore, a large amount of high-quality water has to be withdrawn from freshwater sources for sustain water supply to a city. In order to reduce the demand for freshwater, in addition to water saving, the following measures have to be taken:

Urban Water Use by Quality can become the new manner toward the future for mitigating freshwater shortage. This means that the high-quality freshwater should be preferentially used for drinking purpose. For other purposes of uses consuming considerable amount of water but not really requiring potable quality, such as that for gardening, outdoor washing, and other environmental purposes, water supply from alternative sources is recommendable. There have already been successful cases of dual piping systems in many countries and regions where shortage of freshwater source is a serious problem.
Urban Water Recycle and Reuse is a measure closely related to urban water use by quality and also a measure within the scope of unconventional water resource development. The effluent from domestic wastewater treatment plants, usually after additional water quality polishing, can be reused for almost all non-potable purposes. In addition to centralized water reuse of city scale, decentralized wastewater treatment and reuse is often more appropriate for onsite water recycle and reuse.
Sequential or Cascade Urban Water Use can also be made possible in many cases. There are good examples of household sequential water use, while systematic cascade water use to sustain urban water landscape can be more effective. In such a way, water can be used many times as long as its quality permits. To achieve this, it is preferable to integrate urban environmental water use into urban planning.