Use of Reversed Osmosis (RO) for purification of water is a trend these days. But have you ever imagined how harmful the impurities drained out from the RO units could be if not managed properly? If dumped casually in the open, this impure discharge with high levels of total dissolved solids (TDS) can contaminate both underground and surface water and cause health and environment hazards.
In a place like Dwarka, Delhi, where almost all the societies have their own big common RO plant and where all the households have their own RO unit in kitchen, the impure waste water is drained out from the storm water drains.
Also, people in Delhi and its surrounding areas, who extract underground water illegally to run their business of RO water, are carelessly disposing of the impure rejected water in the environment. At many places, such impure water is injected back into the underground natural water reservoirs contaminating them with high levels of TDS.
Environment Quality Management Consultant, Green Growth Trainer (UNESCAP, AIT Thailand), Arvind Rudra, said, “The problem with the RO is that it is a technology that cleans a little portion of water while leaving a major portion dirty. The dirty part contains highly toxic elements including lead, fluoride, mercury, cadmium, chromium, arsenics etc.”
“The toxins rejected from RO membranes,” he said, “are accumulated and released back into rivers. It sets off a chain reaction leading to disturbing eco system by hampering growth of aquatic organisms and resulting in depletion of dissolved oxygen in the river water. Further, if the TDS increases the sodium absorption ratio (SAR), it will make the water unfit for even irrigation.”
Research has found that the high level of dissolved solid discharged from the RO adversely affects fertility of the soil. By filtering into water sources on the surface of the earth and underground, it contributes to both water and atmospheric pollution.
As regards disposal of RO reject, Rudra said, “It should be stored in cisterns for use in toilets for flushing or irrigation blending with raw water. If TDS in raw water is 500 and in the reject 1,000, we assume 1:1 reject ratio (i.e. for one litre RO product we are generating one litre reject, hence in reject, TDS will be 500+450, which is 950 mg/l). It can be blended with 1:1 raw water and have a TDS of 750 mg/l). If we consume too much of minerals, it will cause physical disorders as excess calcium and iron can cause stone formation in our body and even result in retardation of brain.”
Assistant Professor, Geology, Delhi University, Dr Shashank Shekhar, says, “The rejected waste water can be purified at multiple levels to get highly concentrated TDS liquid. Salt can be further extracted to use rest of the water again. The salt extract can also be disposed of judiciously. So, to use the RO, the community should contemplate on using waste water on a concept of zero discharge.”
“This,” he said, “will not only keep the environment free from pollution, but also save water. I recommend a joint effort by the community and the authorities to ensure proper disposal and treatment of waste water from the RO.”
There are a few societies in Dwarka using waste water for toilet and car wash and other such purposes. Vice-president of New Millennium apartments, Sector 22, MS Suri, says, “We have a common RO plant with a pipeline linked to our toilets. Thus, we try our best to use every single drop of water.”
When asked how they manage waste water, a RO water supplier told City Spidey that there is a pipeline to reach underground water table through which the impure water is injected back into underground. He justified the disposal mechanism calling it the best process to recharge the underground water table.
Such RO companies are mushrooming in Delhi NCR both on paper and without paper. On the other hand, there are established RO companies that claim, on paper, to have a proper waste water management system in place. But nobody knows what they do with the waste water off the record.
“Who cares what is being done with waste water in the industry. Once a paper is prepared, these companies are up to anything. I am sure what they claim on paper is far from truth,” says a water activist.
Acting Director, NEERI, CSIR, Tapas Nandy, says, “There is a big difference between using RO for surface water and underground water. In case of surface water, the discharge would not be of very high solid concentration. But if underground water is used for RO, the discharged water would be of very high concentration of solid which needs to be treated as industrial effluent.”
Since RO is widely used to purify groundwater, the authorities should deal with the menace sternly on two counts. One, extracting underground water is illegal. Two, groundwater used in RO generates more TDS.