Tertiary Treatment By RO
Generally primary and secondary effluent treatments are given by industries to meet the statutory requirements set by State & Central Pollution Control Boards for disposal of industrial effluents. The import parameters which are deciding criterion to evaluate the quality of treated effluents are total dissolved solids (TDS), total suspended solids (TSS), pH, Biochemical oxygen demand (BOD), Chemical oxygen demand (COD), Oil & grease, colour, many heavy metals etc.

The major effort in primary and secondary effluent treatment is directed towards meeting the above-mentioned parameters. Even though it may be possible to achieve necessary disposable quality by primary and secondary treatments the treated water never becomes reusable and therefore it is discharged into sewer/water bodies such as canal/creek/sea/rivers. It is also difficult to monitor the quality of the effluent discharged by individual units about their consistency in meeting the required parameters. As per the existing law water cess is being levied on all the industries which are disposing treated/untreated effluents out of their factory premises.

In order to produce reusable grade water from the primary/secondary treated effluent Reverse Osmosis (as a tertiary treatment) is being used regularly. Incorporation of RO ensures very high quality water which is almost free from colour, BOD, COD, TDS, TSS and other heavy metals etc. This is found to be extremely beneficial as it significantly reduces the water cost of an industry on one hand and achievement of almost zero discharge on the other.

In order to produce reusable grade water from the primary/secondary treated effluent Reverse Osmosis (as a tertiary treatment) is being used regularly. Incorporation of RO ensures very high quality water which is almost free from colour, BOD, COD, TDS, TSS and other heavy metals etc. This is found to be extremely beneficial as it significantly reduces the water cost of an industry on one hand and achievement of almost zero discharge on the other.

In order to provide high feed quality to RO in terms of lowest SDI and lower fowling index Genesis introduced back washable MF/UF in hollow fibre configuration systems for the first time in India in 1994. Even though the utility of such a high quality pre-treatment before RO was not accepted then it has become a Industry standard today.

Membrane Bio-reactor is a combination of two well tested wastewater treatment technologies. Namely Activated Sludge where bacteria consume pollutants resulting in waste minimisation and membrane filtration where separation of clean water from activated sludge is achieved. Following is a schematic illustration on the working of membrane bio-reactor in association with activated sludge process :

In the production of white sugar crystals from cane juice various separation techniques are employed to separate sucrose from those of other components present in cane juice. Since sugar manufacturing is an old process based on conventional techniques the separation efficiency as well as energy efficiency are low. Periodic heating/cooling coupled with adjustments of pH to acidic/basic conditions cause significant loss of the sucrose molecule in to molasses and else where. Incorporation of appropriate membrane technology has been tested to produce sugar with higher yield and with lower energy consumption. The resulting molasses has been found to be of much better quality in terms of colour and salt content. Such molasses will be of very high value for those industries where it is used as feed-stock.

In electrocoat paint systems, the permeate produced by the ultra filter contains water and paint solubilizers. The permeate is used in the paint line rinse section. This recycling method provides a closed-loop rinse system for recovering paint drag-out. The permeate can also be diverted to drain to reduce the conductivity of the paint.

Paint Circulation loops :

Pervaporation is a process in which a specific component in a feed mixture passes through a dense, non-porous membrane by solution – diffusion transport mechanism. Then, the permeate is collected as a vapour at the other side of the membrane while being kept under vacuum conditions.

Some of the Applications include Dehydration of Organic Solvents. The PV process can easily dehydrate solvent mixtures. The binary or ternary azeotropes can be dehydrated without the use of entrainers. In some cases, where distillation is not possible, pervaporation is the only alternative to costly incineration of waste solvent streams.

In addition to above a wide range of organic solvents can be extracted from waste water such as hydrocarbons, chlorinated hydrocarbons, esters, ketones, ethers, alcohols. The PV systems can also reduce COD requirement of waste water streams going to biological treatment units, or pre-concentrate organic wastes to incinerators.

• Superior for azeotropic mixtures
• Pollution free process
• Energy efficient
• Flexibility
• Modular construction