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Forbes Pro's World-Class Water Solutions & Zero Discharge Plants
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Mr. Ganesh Pangarkar,
General Manager,
Forbes Pro Water Projects,
Eureka Forbes Limited |
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The World population is increasing, and with it the energy consumption per head is rising continuously, mainly caused by industrial development. Power production always has an impact on the environment. Besides fuel gas, other emissions - liquid or gaseous - are leaving the power production process. One noteworthy point emission is the water loss of the water/steam cycle. Considerable amounts of water have to be discharged. This water contains chemical impurities. The discharge of these streams means an impact on the environment and often, expenditure also spending for effluent treatment of effluent. Furthermore, water needs to be replaced, which again means additional expenditure and consequently additional waste water from the water treatment plant. An important aspect taking into account that exceeding the natural available water resources also means to influence the environment in a negative way. The principle of “zero discharge” is recycling of all industrial wastewater. This means that wastewater will be treated and used again in the process. Because of water reuse, wastewater will not be released into the sewer system or surface water. The concept of zero discharge system is to ensure that essentially there is no discharge of pollutants into the environment. Recovery of water is of primary importance.
Waste water is collected in the equalisation pond and passed through a series of process equipments. Harmful organic/colloidal contents in the water are separated in the first phase of the treatment, and the inorganic content in the water is separated in the second part of the process. Ultra-filtration technology is used to remove harmful suspended matter in the water which can cause damage to reverse osmosis membrane. A series of reverse osmosis units are used to recover water from the waste water. The quality of product water is better than the raw water in the plant.
The water recovered in the process is 90-95% of the inlet water in the plant. It means only 5-10% water is waste water which is treated further for evaporation.
The remaining waste water is treated using different technology for converting it to solid waste which can be used for land filling activities.
Forbes Pro Water Projects also uses the latest technologies such as Membrane Bio Reactor to recycle sewage and industrial waste water from the plant back to process use. In India, Forbes Pro Water Projects has successfully installed and commissioned the plant based on these technologies.
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Broadly, the process used for this is:
1) Solar Pond Evaporation
2) Mechanical Evaporation using solar pond
3) Thermal Evaporation
The objective of the system is to evaporate the waste water using solar energy for Solid Wastes Disposal option. The high TDS (total dissolved solids) water will be pumped into the solar evaporation pond. Due to a natural evaporation process, a concentration of solids takes place. Once the concentration is reached, the form of salt and solids gets separated and the salt is taken out by scraping the solar pond.
With Mechanical Evaporation The objective of the system is to concentrate the rejects or high TDS streams and make them into a solids/slurry form. The solids/slurry can be disposed off by the Hazardous Solid Wastes Disposal option. The high TDS water will be pumped into the solar evaporation pond. In the first phase of the solar ponds, the pumps re-circulate the rejects a number of times, and an increase in the solids concentration takes place. Once the concentration is reached where the liquid cannot be pumped or re-circulated, the concentrated liquor is taken to the Auxiliary ponds and allowed to dry naturally. In these ponds, no recirculation takes place.
Normally, RO reject water contains minerals & salts in huge quantities. So this water cannot be let directly into the environment. It needs to be treated and made suitable as per environmental conditions. For that we use Thermal evaporation method to recycle the RO reject water. Reject water is collected into a balance tank and fed into pre-heaters (type of shell & tube heat exchangers) where it is heated upto 70-800C with calendria chest vapours to provide the initial preheating, at a cheaper cost. After evaporation, the liquid is separated into vapors & concentrated liquid. Vapors are collected in vapor separators and concentrated liquid is again fed into the next calendria for heating. This process is repeated until a final, concentrated slurry is left. This slurry could be used for land filling.
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Zero liquid discharge minimizes the consumption of freshwater as the cost of treated water is 50% less than that of fresh water. Therefore, by reusing wastewater, it helps relieve freshwater availability limitations in places where it is scarce or expensive. Thus, considerable savings are realized and that resulted in a moderate payback period. In addition, elimination of liquid discharge also helps towards the need to comply with increasingly stringent environmental restrictions.
Purchased water, wastewater treatment, and disposal costs are significant. Thus, savings associated with minimized new water requirement and wastewater flow can justify capital expenditures to minimize. In the case of new constructions, zero liquid discharge can save money on real estate costs, since location near a suitable water resource would not be necessary.
Forbes Pro Solutions, a part of Eureka Forbes Limited, provides health and hygiene solutions to industrial and institutional customers. Forbes Pro's world-class solutions are Desalination Plants, Effluent Treatment Plants, Membrane Filtration, Sewage Treatment Plants, Zero Discharge Plants and other such systems. Forbes Pro, as part of this gigantic enterprise, has executed and maintained projects for companies across the globe. The company caters to industries around the world -- like Food & Beverages, Metal & Steel, Automobiles, Power, and Chemicals, etc.
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