Due to its unique properties and low cost, water is widely used in industry as a working fluid. Its treatment after use (cleaning, cooling) makes it possible to create a reverse water supply with repeated use. Due to this, water consumption is significantly reduced, and environmental pollution is also prevented. As a result, comfortable conditions are created for people to live.
Operating principle
The water supply system must be constantly replenished and periodically updated. Water is mainly used as a cooler or coolant. In each case, it is pre-cooled or heated. Before reuse , water can be cleaned, as it is contaminated by the products of technological processes.
The share of recycled water supply is increasing in all industries. The liquid is most often used in heat exchange equipment. Water is repeatedly subjected to heating and cooling in spray pools or cooling towers. Most of it is lost in the process of evaporation.
Recycled water supply to a chemical production plant is already 98%. There it is used in technological operations where water treatment from industrial waste is required.
Separation of sludge from water makes it possible to process and extract valuable components.
Water consumption
Water is used everywhere for cooling mechanisms and machines in production processes. For the processing of 1 m 3 its oil is required in 2.5 m 3 . For a refinery, the daily demand for water is huge and discharging into the sewers is unacceptable. Therefore, it passes through treatment facilities and is reused. The reverse water supply for the CHP works on the principle of steam generation, its supply to the turbines and condensation in the cooling towers, after which the water goes back to work.
In everyday life, many of these technologies are not of interest. But the owners of small enterprises are constantly faced with the need to use recycled water in car washes, in pools, in laundries, etc.
Water use patterns
2 circulating water operation schemes are applied:
- no treatment after use;
- with intermediate processing.
In the first case, water can be used after the process, when it maintains acceptable performance. For example, containers are washed with drinking water, after which it can be used for other household needs in the household, and the excess is discharged into the sewer. For industrial enterprises, such a scheme is usually unacceptable.
Enterprise water supply scheme
Reverse cycle water must meet certain requirements:
- lack of negative impact on product quality;
- salt deposits should not form in the system;
- low corrosion effect on equipment;
- lack of biological fouling system.
The industrial water recycling system collects and accumulates most of the impurities in the receiving waste water sumps and in the cooling tower tanks.
Tanks are cleaned periodically manually or by mechanization of the sediment removal process without stopping the system.
Water treatment
During evaporation, calcium salts accumulate in the circulating water, which are deposited in pipes and on heat exchangers. They also precipitate as a result of heating the water, when the solubility of the gases decreases and the hydrocarbonate ions decay, forming an insoluble precipitate.
Carbonate deposits prevent acidification, phosphation, recarbonization and water softening. Acidification is a common method, due to its low cost and ease of implementation. It is important to observe the dosage of acid to prevent corrosion of the equipment.
Recarbonization of water is carried out by treatment with carbon dioxide. For this, flue gases purified from ash are used, which are mixed with water using ejectors or bubblers laid at the bottom of the tank.
Phosphating water requires a small consumption of reagents (1.5-2.5 g / m 3 ), but the costs are still large. The advantage of the method is the absence of aggressive properties of the solution.
If there is sufficient oxygen and organic matter in the recycled water, the equipment may build up. This leads to a deterioration in heat transfer and an increase in hydraulic resistance in pipelines. Chlorination of water and the addition of copper sulfate are used to combat fouling.
Which systems are better?
The use of water recycling systems entails significant costs for their creation and operation. At chemical plants, production products pollute recycled water. The centralized system takes up large volumes, where a complete replacement or high-quality purge is sometimes impossible.
Efficient operation of circulating systems is achieved by combining closely located consumers with similar operating modes in groups with small-capacity water chillers. Local systems provide the optimal operating mode for each consumer.
Car wash water supply system
The reverse water supply for car washes and other small enterprises is being developed with the complete elimination of the possibility of discharging sewage into the sewer. Water does not change its quality and can be used in a closed system.
Advantages of local treatment facilities:
- reduction of water consumption up to 90% with replenishment of water losses;
- lack of ablation of wastewater;
- environmental friendliness.
In all systems, sedimentation and filtration are used as the main cleaning methods. A widespread installation of recycled water supply AROS and the like.
Drains containing oil, dirt and fuel enter the sump and pass through 3 treatment sections with upper and lower overflow.
The sump is not included in the package. The water recycling system contains it as a basis. It is designed and manufactured in accordance with the recommendations of the treatment plant manufacturer. For a sink with one post, the volume of the sump is 6 m 3 .
Settled water is supplied by a submersible pump from the last section to a sand and gravel filter to clean the remaining solids and then to a storage tank. The installation can be equipped with a filter column with a sorbent for removing petroleum products.
The system provides for the automatic supply of a solution of hydrogen peroxide or other sterilizing agent with a metering pump , which ensures the destruction of microbes and unpleasant odors. Ultraviolet lamps mounted above the sump can also be used for this.
From the storage tank, water is supplied for reuse, passing through a fine filter cartridge. The liquid level in the tank is automatically controlled.
The Skat water recycling station works in a similar way. It is available in floor or underground design. Layout options provide for deep sewage treatment with or without it. Structures trap solids, oils, petroleum products and organic impurities.
Equipment for compact sewage treatment plants
The reverse water supply of small industrial enterprises includes the following equipment.
- The submersible pump is suspended on a cable in the finishing section of the sump. Connection to the pipeline is carried out using adapters and a flexible hose. Management is made from a distribution cabinet. Dry float sensor is provided.
- The pressure boosting module includes a pump, a pressure gauge and a buffer tank. It allows you to maintain a constant pressure of the water supplied to the sink.
- The filter column is a cylindrical container with a filler, an air vent valve and a switch for backwashing.
- Purified water is collected in a storage tank. Above it provides for the introduction of a sterilizing reagent. Water level control is carried out by sensors.
- Automatic pump control is carried out by an electronic system. On the front panel of the control cabinet there are indicators and switches, with which the operator sets the operating modes of the system and controls its operation.
Recycled industrial water supply systems for washing automobile and railway vehicles can provide deep wastewater treatment with their discharge into the sewers.
Conclusion
Recycled water supply is created with the aim of environmental protection, profitability, and also in case of emergency, caused by the creation of a small enterprise. Profitability is determined by design calculations. In the future, it will only increase due to an increase in the cost of water and an increase in fines for environmental pollution.