Conserve or Perish

Water, a rapidly dwindling resource, supports a few critical processes in cement manufacturing units. Many cement industry players have been constantly upgrading their water management systems.

India is faced with a crisis on its water resource management front. This crisis arises from lower availability, increasing demand, polluted water bodies and inadequate storage. There is a general consensus that by 2050, India?s water demands will exceed all available sources of supply. Current water development and management is not sustainable; unless dramatic changes are made – and made soon. Water continues to rise as a priority for India and Indian businesses in a scenario where more than 80 per cent of river basins are facing water stress and scarcity, groundwater quality is fast deteriorating, non-point source pollutants (nitrates, phosphates) are increasingly contaminating freshwater and about 50 per cent of riverine length shows high pollution measured in terms of BOD alone. Given the above increasing water stressed scenario, ensuring prudent use of available water resources has emerged as a key dimension for minimising future risks to business operations.

Cement
Water is the most important ingredient sustaining many processes of mining and cement manufacturing units. Water intended for human consumption should be safe and wholesome, i.e., free from pathogenic agents and harmful chemicals, pleasant to taste and usable for domestic purposes. Urban and rural India depend heavily upon various types of water bodies to meet their daily requirement of water. This is a highly worrying fact as the role of ponds in the urban and peri-urban milieu is multifaceted. It is just not a pool of water, as this pool may not be considered as playing a very major significant role of social, ecological and civic importance. The environmental pollution as a result of the cement industry could be defined as an undesirable process that is responsible for water, air and land pollution through its various activities, right from the mining activity of the raw material (limestone, dolomite etc.,) to its crushing, grinding and other associated processes in a cement plant.

Water conservation among multinational cement producers has become increasingly high-profile in recent years. Cement production requires water for cooling heavy equipment and exhaust gases, in emission control systems such as wet scrubbers, as well as for preparing slurry in wet process kilns.

Today there are still wet and dry cement technologies, but the technologies in wet process kilns are becoming obsolete and progressively being replaced by more efficient dry process kilns

The amount of water used varies widely across the industry, depending on the specific processes operated at each site, the equipment used, and the prevailing management philosophy concerning water use. Major water uses in the cement manufacturing industry may include:

1.Raw mill
2.Coal mil
3.Dust suppression
4.Washing/rinsing/hosing
5.Cooling
6.Boilers

Specific Water Consumption
There is a clear reducing trend observed in the specific water consumption (SWC) over a scale of 0-0.5 m3/MT and a time period of five years as shown in the graph. There has been a 6 per cent reduction in the annual SWC in the past five years. This is due to the fact that industries have been constantly upgrading their water management systems, adopting latest technologies, and some companies have shown the way towards practicing excellence in their water management.

The data reported (refer to Figure 1) does not include water supply to nearby communities and colonies for domestic applications and is calculated based on water consumption inside the plant only.

As is clearly seen from the Figure 2 map, most cement industries lie in the areas which have low net groundwater availability (<29,179 HAM or 291.8 MCM). Therefore, continuous high ground water withdrawals can lead to an alarming deficit between demand and supply in the near future. So cement industries should look forward to using water from alternate sources (if available) to avoid overexploitation of groundwater resources.

Audit findings and achievements by CII-TWI
CII – Triveni Water Institute has a vast experience of conducting water audits for cement industries with different capacities and spread across regions.

During the water audits, considerable opportunities for water saving have emerged:

• 5-10 per cent saving by low-medium cost strategies; payback less than a few months
• 20-25 per cent water saving by high cost strategy; payback within two years

Recommendations

• Reducing water use by integrating processes together
• Improving cycles of concentration in cooling towers
• Reuse of filter backwash water
• Installation of air-cooled condensers in place of water-cooled condensers
• Utilisation of boiler blow down water in cooling towers
• Closed loop cooling system for pump gland seal cooling
• Re-use of RO reject water for cement mill spray
• Reduce domestic water consumption in plant by installing water-saving devices
• Reuse of treated water using advanced technologies (RO DM) for high-end applications
• Recycling of sewage water for low-end applications (gardening, etc.)
• Mist-type dust suppression system in tankers
• Water conservation by rainwater harvesting

CII – Triveni Water Institute water audits have been held across different sectors that include automobiles, pulp & paper, pharmaceuticals, engineering, food and beverages, power plants, etc., with different capacities, processes and spread across regions.

The audits have translated into the following estimated annual benefits:

• Potential water savings of about 85 billion litres (as on May 2015)
• Sensitisation and training of 5,000+ industry personnel on industrial water and waste water management
• Facilitation/identification of approach for achieving zero water discharges.

Action agenda

• Utilisation of boiler blow down and recovery of flash steam through heat exchanger
• Reduce the makeup water of cooing tower by increasing the cycles of concentration
• Reduce domestic water consumption in plant by installing water-saving devices
• Closed loop cooling system for pump gland seal cooling
• Utilisation of ETP treated (secondary clarified) water for high-end applications (boiler feed, cooling tower etc.,) using RO-DM combination
• Collection and reuse of steam condensate from steam traps in plant
• Recycle WTP and DM plant filter backwash water
• Recycling of sewage water for low-end applications (gardening, etc.)
• Utilisation of ETP-treated water for dust suppression.

Management of water in the cement industry needs:

• To reduce water consumption through process improvements and implementation of recycle and reuse of water.
• Technological upgradation/measures for reduction in water consumption for achieving the benchmark/overall goal.
• To have quantum improvement on the individual ETPs by adding tertiary treatment units. This would result in producing industry-grade water from excess back water discharged from various processes reusable within the industry.
• A strict metering of the water used and wastewater generation is recommended.
• Undertake regular water audit for streamlining activities and sustaining benefits of the study in the long run. Periodic (every two years) third party audit recommended.

(This article has been authored by Sanjay Gupta, Head – Advisory Services, Confederation of Indian Industry (CII) – Triveni Water Institute, Jaipur).