Increasing regulatory pressures, aging infrastructure, and environmental concern are forcing organisations to reassess the impact of water management on their economic wellbeing.
In India, population growth and overall economic development are expected to lead to an increase in water usage across sectors. Available resources are likely to be overexploited with a rise in the consumption of water for irrigation, Industrialisation and infrastructure growth. Industry bodies are encouraging companies by recognising their proactive implemen¡tation of sustainable water management programs and large Indian companies are investing in multiple water management initiatives across their operations. In a large developing country such as India, the links between water consumption across sectors complicates water management and rapid industrialization and unplanned urban growth is resulting in the generation and discharge of large quantities of wastewater into existing water bodies. This untreated wastewater is leading to increased pollution and depletion of clean water resources.
Godrej & Boyce has achieved ´Zero Discharge´, since 2010, for its industrial activities by effectively treating and recycling of industrial effluent generated through various activities. A total of around 15 lakh liters/day of treated waste water is recycled back for use in Process in Pre-Treatment (PT) line after treatment through RO systems, RMC production and Landscaping applications. By making use of recycled and ground water for our cooling applications we have reduced the use of about 3 lakh liters per day of good potable water which was lost due to evaporation and drift. If this is not enough, we are using recycled water for new constructions as for production of ready mix concrete.
The everyday requirement of 2-3 lakh liters perday of water for RMC production at two plants is sufficed by recycled water. The organisation has not only taken various initiatives in our manufacturing units, but also in our residential colonies in Vikhroli. One among the many is the construction of sewage and recycling plant with a distribution network for using it for flushing of toilets in our residential colonies, which reduces about 5 lakh liters per day of good potable water use. Other very significant initiative which has been taken is the Rainwater Harvesting.
As a part of the on-going efforts, the company decided that the Godrej IT Park Project, 02, Godrej Business District which is a part of our Vikhroli township recycles 100 per cent of sewage water generated from the building by reusing the same for its flushing, gardening and landscaping requirements after adequate level of treatment in a sewage treatment and recycling plant. This project has received LEED certification for achieving the required green standards.
An overview of the process
The treatment procedure used in this project was a ´completed mixed aeration system´, which uses submersible non-clog sewage pumps to pump the sewage from the collection sump. The pumped sewage is then taken to an overhead holding tank before it is drained by gravity to an open RCC basin to be treated biologically by highly efficient diffused aeration system.
After a certain period of aeration, the sewage settles down and can be decanted and collected in a decantation tank from where it is pumped through a filter package consisting of pressure sand filter and activated carbon filter. These are then sent to the treated water storage tank after disinfection by sodium hypochlorite. After that, tank chlorination is done to this treated water by using hypochlorite solution for disinfection.
Unlike commonly used aeration sewage treatment plant, this process utilizes the same tank for aeration and as well as settlement purpose, thereby doing away with a separate civil structure for the settling tank and also the settling tank machinery and return sludge pumps. Also, the variation in the flow rate creates malfunctioning in conventionally designed settling tank of regular extended aeration process. As a result, during maximum sewage flow rate there is a carryover of the sludge together with the treated effluent thereby causing higher BOD in treated sewage.
This process also ensures that there is intermittent operation of the process and the entire area of the aeration tank is utilised during settlement stage. This makes sure that all the mixed liquor and suspended solids which are formed during aeration step settles down under quiescent condition during the settling stage, allowing clear treated effluent to pass to the decantation tank during the decantation step. Thus, there is no carryover of the sludge in the treated water and the BOD of the treated water is thereby low and within prescribed limits by the pollution control board.
This case study has been co-authored by Rumi Engineer, Head of Green Buildings at Godrej Green Building Consultancy Services & Head of Energy Conservation, Godrej & Boyce Ltd. and Tejashree Joshi, Asst. General Manager, Environmental Engineering Services