Ganesh Pangarkar General Manager-Forbes Pro Water Projects, Eureka Forbes Limited
WASTEWATER is collected in the equalisation pond and passed trough series of process equipments. Harmful organic/colloidal contents in the water are separated out in the first phase of treatment and the inorganic content in the water are 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. Series of reverse osmosis units are used to recover water from the waste water. The product water is better in terms of quality than the raw water to the plant.
The water recovered in the process is 90-95% of the inlet water to the plant. It means only 5-10% water is the waste water which is treated further for evaporation.
The remaining wastewater 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 latest technologies such as Membrane Bio Reactor to recycle the sewage water and industrial wastewater from the plant to recycle back to process use.
Broadly the process used for this are
- Solar Pond Evaporation
- Mechanical Evaporation using solar pond
- Thermal Evaporation
[box type=”shadow” ]The principle of “zero discharge” is recycling of all industrial wastewater. The zero discharge system essentially ensures no discharge of pollutants into the environment and recovery of water. There are different processes used to recycle wastewater for reuse.[/box]
Solar Pond 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 natural evaporation process the solids concentration takes place.
Once the concentration is reached the form of salt solids gets separated out and the salt is taken out by scrapping the solar pond.
Solar Pond with Mechanical Evaporation
The objective of the system is to concentrate the rejects or high TDS streams and make it in the solids/slurry form. The slurry/solids 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 and increase in the solids concentration takes place.
Once the concentration is reached where the liquid cannot be pumped or recirculated, the concentrated liquor The water recovered in the process is 90-95% of the inlet water to the plant. It means only 5-10% water is the waste water which is treated further for evaporation. is taken to the Auxiliary ponds and allowed to dry naturally. In these ponds, no recirculation takes place.
Thermal Evaporation
Normally RO reject water contains minerals & salts in huge quantity. So we cannot directly let this water 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 balance tank and fed into pre-heaters (type of shell & tube heat exchangers) where it is heated up to 70-80oC with calendria chest vapours to provide the initial preheating at cheaper cost.
After evaporation, liquid is separated into vapours & concentrated liquid. Vapours are collected in vapour separators and concentrated liquid is again fed into next calendria for heating. This process is repeated until final concentrated slurry is left. This slurry could be used for land filling
Financial Advantage
Zero liquid discharge minimizes the consumption of freshwater as the cost of treated water is 50% less than the fresh water intake; therefore by reuse of 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.
Environmental Impact
Purchased water, wastewater treatment and disposal costs are significant; thus, savings associated with minimized new water requirement and wastewater flows 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.
