URM is now a Zero Liquid Discharge Unit

Central Chronicle News
Bhilai, Jul 23: In a significant initiative for waste water management, SAIL-Bhilai Steel Plant’s Universal Rail Mill (URM) has started recycling its major backwash water from Scale Removal Filters to become a Zero Liquid Discharge Unit. Underground pipe line were laid across two different units at URM recently to recycle backwash water from filters to primary settling tank, with in house resources.
URM which produces world class rails has its own Water Treatment Plants which are supplying different qualities of water to cater the various needs of Re-heating Furnace & Mill.As per system requirement, scale removal filters (SRF) & HYDAC filters need to be cleaned (Back washed) regularly in each shift for their efficient working. Back wash water of these filters used to go outside plant via Outlet-B. Recently, after some brainstorming and discussion, URM Team decided to undertake and establish a process to bring back this water back into the system. HYDAC filter backwash water of direct cooling water circuit (WTP-3) which was going to the rainwater storm drain has been diverted to the secondary settling tanks. This could be done because of high residual pressure in the filter line. Similarly, HYDAC filter backwash water of indirect cooling water circuit (WTP-4) which was going to the rainwater storm drain has been diverted to the overhead filling sump.
From here this water is being filtered through pressure sand filter and sent to overhead tanks for use in backwashing of filters. Re-routing of a large volume of backwash water of Scale Removal Filter was a major challenge since it had fine scales and residual pressure was very nominal. Detailed engineering was done to assess the capacity of WTP-1 for taking the additional load of back wash water. Contouring of the area was done and survey points marked.
Different lay-outs were studied and the one having minimum bend and length was selected for laying 80m length of 300mm dia pipe from Scale Removal Filter to WTP-1 primary settling tanks. All the 8 Scale Removal Filters backwash outlets were connected to this pipe and valves provided at suitable locations for diversion of water.
The Plant’s Civil Engg Dept (CED) provided all support for execution of the job i.e., excavation of trench and concrete breaking in very short time. Care was taken to maintain uniform gradient of the pipe and also all obtuse bends were provided to minimize the loss of energy. This experiment proved to be successful and almost 80cum/hr water is now recycled through gravity only. This additional water drastically reduced the need of makeup water in Water Treatment Plants. For this, one more modification was necessitated and a pipe of 120m length of 80mm dia was laid from the header of direct cooling water to the overhead filling tank pipe.
Care was taken to tap this line after HYDAC filter so that only filtered and clean water goes to the overhead tank. Since this header line has a pressure of 8kg/sqcm, it was possible to fill overhead tanks at a height of 40m without any pumps. Earlier industrial makeup water was used to fill Overhead Tank and backwash filters. Now with this modification, the need for Overhead Tank filling pumps is eliminated and recycled backwash water is directly filled in Overhead Tank and then used for filter cleaning.
Concerted efforts by URM Team along with other agencies involving a minor engineering change in layout is helping URM to save lot of makeup water. Among the key benefits are – major environmental concern of back wash water going outside plant through Outlet-B has been permanently addressed; recycling of 80 cum/hr of backwash water from SRF; elimination of 80cum/hr of makeup water by treating this recycled backwash water and reusing it in cleaning of SRF – scale removal filters; waste water recovery system from water treatment cycle eliminated resulting in elimination of operation and maintenance of three (3nos) of waste water pumps; overhead tank filling system through pumps eliminated resulting in elimination of operation and maintenance of three (3nos) of over head tank filling pumps; use of two numbers of PSF – pressure sand filter and two numbers of blower is also not required, thereby resulting in regular saving in terms of maintenance; existing pumping facility of WTP-1 is only used and no additional pumps installed for recycling purpose, thereby resulting in saving not only of electricity and water but also saving in terms of spare parts. All these modifications would result in estimated saving of Rs 1.5 Crore per annum.
Congratulating Anish Sengupta CGM URM, Sanjay Kumar GM, other members of Team URM, CED, EMD and Projects, AK Bhatta, ED (Projects) stated that the initiative to take backwash water by laying pipeline from scale removal filters back to WTP 1 primary settling tank, thus preventing zero discharge of scale and sludge to outlet B will go a long way to achieve the objective of zero liquid discharge plant.

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