Reducing Water Use In The Chemicals Industry

Last updated: (February 2005)

Introduction

Water could be costing your company over 1% of business turnover. Yet by using some simple control measures and inexpensive devices, this can be reduced by as much as 50%. These savings go straight to your bottom line as well as reducing environmental impact. This briefing note explains how you can tackle water costs and start saving money.

Background

Water is a utility that is paid for twice – once on purchase and once on disposal. It is still viewed by many as a free resource, because as individuals we rarely have to account for its usage at home. Yet water costs can form a significant fraction of operating costs in many industries and is a utility where simple control measures can have a major impact on cost reduction.

How Much Does my Water Cost?

The cost of water varies from region to region, but typically industry pays between 60p and ?1 per m? to purchase water from a water company. Additionally, where effluent is discharged to sewer, the cost of treatment may be over ?1 per m?, depending on the level of waste water treatment provided by the local sewerage company.

Yet water costs do not only consist of purchase and disposal costs. On site, water must be stored, treated, pumped around, and heated or cooled. Additionally, the storage and handling plant must be maintained. Finally, losses through leakage and spillage may not only increase water costs, they may also waste valuable raw materials and products. A reasonable estimate of the true cost of water is around three times the cost of purchase and disposal.

Where is it Used?

The most common use of water in the chemical industry is for cooling and steam production, closely followed by its use as a raw material. Other significant uses include plant and vessel washing, product washing, vacuum pumps and air pollution control (eg gas scrubbing).

Despite so many varied applications, water is often only metered as it comes onto site for billing purposes. Process usage may be metered, as it may be critical to product quality, and many sites are now aware of the need to meter steam usage for energy efficiency programmes. But cooling water flows are rarely measured, and the use of manual hoses to wash down equipment and surfaces is an invitation to use water indiscriminately.

A further justification for a comprehensive metering system is the location of leaks. Many chemical plants have developed over a period of years and underground water mains are very common. Without a regularly updated distribution network diagram and clear metering to enable a full water balance to be constructed and reconciled with the water bill, leaks can go undetected for years. Underground leaks can also have much more serious impact, including possible erosion of foundations and roads and, if the leak becomes a serious burst pipe, production losses while the main is excavated and repaired.

What Happens When I Have Finished with It?

Most water used in the chemical industry is used once only. After use it is simply discharged to drain and either to sewer or an on-site treatment plant. But it may be perfectly adequate for re-use in another process or as wash water before discharge. A "water cascade" can provide opportunities for several cycles of re-use before it becomes too dirty and must be discharged. Yet every time that water is re-used, an equivalent volume of clean water does not have to be bought. It doesn’t take long before water consumption is cut by 50%, 70% or even 90%.

How Can I Reduce my Water Use?

The first action must be to draw up a water balance for the site. This will show how and where water is being used. It will highlight the largest users and indicate where any leaks may be undetected. Following this, a simple housekeeping programme can be instituted to generate immediate savings, raising staff awareness of the commercial importance of water savings and providing a "fighting fund" for more capital-intensive measures.

Simple housekeeping measures which have been used in the chemical industry include:

• leak detection programmes
• triggered hoses
• improved cleaning procedures
• valve, pipe and pump maintenance.

Once the water balance has been completed, it is important to update it regularly so that the impact of any activities can be seen by all. This naturally leads on to setting targets for production and ancillary use with which progress can be monitored and savings verified.

Sooner or later, however, capital investment will be required. Some of the most common measures taken by the chemical industry include:

• condensate recovery and recycling as boiler feed water
• condensate recovery and recycling as process water
• replacement of once-through cooling water systems with recirculating systems
• upgrades of liquid ring vacuum pumps to use recirculated water
• recovery of filter wash water for process use
• recovery of process water of plant washing
• local effluent treatment facilities to recover high quality water.

The construction of a "water cascade" to identify the available effluent streams and match them with the process and ancillary water demands is an effective tool for matching water supply and demand. Using a method known as "Water Pinch", it is possible to identify what available water quality is suitable for which service and design a water recovery network accordingly. This is described more fully in an ETBPP New Practice Case Study (NC55 – Water pinch study pays major dividends).

Benefits

The ETBPP offers many case studies where companies have achieved major savings after adopting a range of water saving measures. A list of these case studies is given later. Here are a selection

Legislation

Most chemical companies are classed as "Part A" processes under the Environmental Protection Act 1990 and as such are required to operate under an Integrated Pollution Control (IPC) Authorisation issued by the Environment Agency. This regime is gradually being replaced by an extended system of Integrated Pollution Prevention and Control (IPPC), in compliance with European Union Directive 61/96/EC. This directive extends the remit of the Environment Agency to include energy efficiency, noise and vibration, site restoration and major environmental accident planning.

IPC and IPPC encompass most of the critical environmental legislation applicable to the chemical industry.

The Future

Although IPPC applies now to all new processes, existing processes will be expected to comply with the new authorisation conditions in 2005 and 2006. This is to allow the appropriate Guidance Notes to be prepared by the European Environment Agency.