5.9 Integrated water conservation - Bhilai steel plant, India

Introduction

Bhilai and its adjoining areas in the Durg and Raipur Districts of Madhya Pradesh State in India experience severe water shortages. For example, in 1988, the Bhilai area, in the vicinity of the steel plant, received only 636 mm of rainfall, compared to the long-term average rainfall of 1 300 mm. As a result, the reservoirs of the Mahanadi Reservoir Project and Tandula Complex, which supply water to Raipur and Durg Towns and village nistari tanks for irrigation, industries and drinking purposes, were reduced in volume to 22.3% of their full supply capacity, or to a live storage of 391 million m³. In comparison, the annual consumption of water at the Bhilai Steel Plant during the previous financial year (1987-88) was 297 million m³. Given the available storage in the reservoirs in 1988, it became essential to reduce the consumption of water until the next monsoon.

Technical Description

As a first step in preparing a comprehensive strategy for managing water resources at the Bhilai Steel Plant, an inventory was prepared identifying areas in the plant where reuse and recycling could be achieved, and an audit conducted of water uses to identify areas in the plant where water consumption could be reduced. In terms of these studies, a number of rain water outlets in the plant, carrying substantial quantities of effluent, which had a potential to be recycled, into the Marida-I Reservoir, were intercepted and diverted to various pump houses so that their recycling was possible. Similarly, the ash slurry from Power Plants-1 and -II was conveyed to an Ash Pond (No. 2) for settlement of solids and recycling of the clarified water. Approximately 1 000 m³/hr was conserved in this manner and returned into the pressure mains for reuse in the Rolling Mills area of the plant. Likewise, the Horizontal Secondary Settling Tanks (HSST) and the overflow channels were found to be poorly maintained, resulting in substantial spillages, which were eliminated by cleaning the return channels so as to ensure that the settled water is contained within the rain water outlet system for later recovery. Additional reenforced concrete pipes were laid to interconnect the rain water outlets to avoid any effluent spills. In addition to the effluent recycling from selected outlets, seepage from the Marida-I Reservoir was also intercepted and routed via the pump house into the recycling system, and water discharges from the Plate Mill, previously routed to a subsoil soakaway, were diverted as make up water to the circulating water pump house at the Plate Mill and to the CAS-III Pump House. The water supply to the townships was also checked and the supply hours were reduced to an half hour in the morning and an half hour in the evening. Such a practice did not cause any serious inconvenience in the townships but helped conserve 1 000 m³/hr of water.

In addition to the recycling schemes, other actions designed to reduce water consumption were also taken, including stopping the water supply to any Mill that was taken out of production for whatever reason; stopping overflows from the suction pumps in the pump houses and cooling towers; improving maintenance of, and stopping leaks in, industrial water supply lines; isolating damaged lines to stop wastage; minimizing the use of water by the Horticulture Department for gardening; and, using posters and public announcements to raise awareness of the need for water conservation amongst staff and township residents.

Extent of Use

All the major schemes were completed within five months. There was no major resistance to the water conservation measures from the staff of the plant or from the residents of the townships towards water conservation efforts.

Operation and Maintenance

The major operation and maintenance aspects considered were "good housekeeping" at the facility, constant monitoring and preventive maintenance to minimize losses through leakages, improving operations and supervision of the pumping stations, and monitoring of concentrations of potential pollutants in the effluents and the quality of the Maroda-I Reservoir.

Level of Involvement

The public sector was completely responsible for the implementation of the recycling and conservation programme at the steel plant. However, community involvement was important in conserving water in the residential townships.

Costs

The capital costs incurred for water conservation at this facility included procurement and installation costs associated with the upgrading of pumping facilities prior to implementation of the recycling programme. In addition, costs were incurred for pump operation, for cleaning and maintenance of the effluent and water pipes, and for descaling and the removal of sludge from pipes. The actual cost figures are not available.

Effectiveness of the Technology

Due to the implementation of the water conservation strategies, the industrial make up water consumption was reduced from 16 740 m³/hr to 3 000 m³/hr at the additional cost of pumps, interconnecting pipes, cleaning and pump operation. Table 35 shows that the industrial water consumption per tonne of steel produced has been reduced from 52.2 m³ to 9.3 m³, a substantial reduction in water use.

Advantages

The advantages of implementing water conservation measures include a lower water supply costdue to a five- to tenfold decrease in water consumption, the ability to continue operations despite reduced water resource availability, the conservation of 14 000 m³/hr of water, an heightened awareness of the need for water conservation amongst the plant staff as well as the residents of the township, and a priority being given to water conservation by the senior management.

Disadvantages

Amongst the disadvantages were an increase in hardness, and suspended and dissolved solids and chloride concentrations in the plant effluent which required increased monitoring to meet pollution control and process water quality standards and an increased frequency of backwashing ion exchange columns, and which led to a marginally greater degree of impairment of water quality (particularly, increased turbidity) in the Maroda-I Reservoir. To mitigate the latter impact, sodium metaphosphate has been added to the Maroda-I Reservoir to inhibit turbidity and discourage scaling in the pipelines by forming a film within the pipes. A further disadvantage of this technology was that, as the water conservation measures use pumping as the principal means of circulating the recycled waters, the water conservation system incurred higher energy costs.

TABLE 42. Reduction in Water Consumption at the Bhilai Steel Plant.

Further Development of the Technology

Water conservation efforts within public sector enterprises such as Bhilai Steel clearly demonstrate that significant opportunities exist for the conservation of large quantities of water, in this case 14000 m³/hr, using relatively simple methods such as better maintenance, reuse of process water, and recycling. However, it is also important to concomitantly explore water reduction, through technological modifications, for example, in addition to focussing on reuse. Such a strategy, in the longer term, could reduce the relatively high operating costs of the recycling-based scheme to a great extent.

Information Sources

Tambe, G.N. 1990. Journal of Indian Water Works Association, Jan-March, pp. 33-36.