TRACKING WATER USE TO CUT COSTS

Transcription

1 GG152 GUIDE ENVIRONMENTAL TECHNOLOGY BEST PRACTICE PROGRAMME TRACKING WATER USE TO CUT COSTS GOOD PRACTICE: Proven technology and techniques for profitable environmental improvement

2 TRACKING WATER USE TO CUT COSTS This Good Practice Guide was produced by the Environmental Technology Best Practice Programme Prepared with assistance from: Dames & Moore Crown copyright. First printed March This material may be freely reproduced in its original form except for sale or advertising purposes. Printed on paper containing 75% post-consumer waste.

3 SUMMARY A water balance is a management tool that provides managers with an overview of the major uses of water on their company s site. When used to control water use and effluent generation, a water balance can help all sizes and types of company to reduce water use, cut costs and increase profits. Adopting a systematic approach to water reduction typically results in a 20-50% fall in water consumption. This Good Practice Guide describes a six-step procedure for constructing a water balance and explains how a water balance can help you to identify water and cost saving opportunities. Checklists and worksheets are provided to help you carry out more detailed investigations of your water use and effluent sources. Examples of cost savings already achieved by companies are given throughout the Guide. A companion Good Practice Guide (GG67) Cost-effective Water Saving Devices and Practices describes in more detail how to implement measures to save water. This Guide is available free of charge through the Environment and Energy Helpline on freephone

4 CONTENTS Section Page 1 Introduction What is a water balance? Why produce a water balance? How to use this Guide 3 2 A six-step procedure for constructing/using a water balance Step 1 - Obtaining top-level commitment and assessing resources required Step 2 - Preliminary review Step 3 - Drawing the picture Step 4 - Adding the detail Step 5 - Using the water balance to save money Step 6 - Continuous improvement 28 3 Dealing with more complex sites Gathering more data Finding out more about effluent flows Using the water balance to save money 33 4 Action Plan 36 Appendices Appendix 1 Where do businesses use water? 37 Appendix 2 Producing and using site drainage plans 40 Appendix 3 Blank worksheets 41 Appendix 4 Example water balances 45 Appendix 5 Calculating water flows for cooling towers/steam relief valves 47 Appendix 6 Determining the amount and cost of pollutant loads 49

5 1 INTRODUCTION Most companies know how much water they use, but few use this knowledge to help them reduce the amount of water used. Companies that adopt a systematic approach to water reduction typically achieve a 20-50% decrease in the amount of water used. By using less water, companies save money on both water supply and effluent disposal. Taking action to save water may also allow companies to recover raw materials or product previously lost in effluent streams. 1 This Good Practice Guide, which applies to both industrial and commercial sites, will help you work out where water is being used and where less water could be used. Savings can be made by companies of any size or type - including companies that use comparatively little water per site or per person. 1.1 WHAT IS A WATER BALANCE? A water balance is a numerical account of where water enters and leaves your business and where it is used within the business. It typically contains information about the amount of water used by each main process and may, for some processes, be very detailed. Presenting the water balance as a diagram makes it easy to understand and use as a management tool. It is best to start by looking at your company as a whole and then adding details as you go along. It is also helpful to think of your site or company as a series of blocks, with each block representing an activity or location with water inputs and outputs. Fig 1 overleaf shows water inputs and outputs for a fairly simple site and Fig 2 is a block representation of this site. 1.2 WHY PRODUCE A WATER BALANCE? A water balance helps you to: understand and manage water and effluent efficiently; identify the areas with the greatest opportunities for cost savings; detect leaks. Small brewery saves money by stopping leaks Monitoring water use allowed J W Lees & Co (Brewers) Ltd to discover a significant water leak which was due to three faulty control valves. The valves were replaced at a total cost of 400, leading to an immediate saving of /year in reduced water and trade effluent charges. For more details, see Good Practice Case Study (GC41) Family Brewery Makes Big Water Savings. 1 1 Available free of charge through the Environment and Energy Helpline on freephone

6 Water supply Meter Liquid raw materials Evaporation and steam Factory laundry and washrooms Factory Factory shop and canteen Water in the product Domestic wastewater/ trade effluent Fig 1 Water inputs and outputs for an example site Mains water Meter Liquid raw materials Evaporation and steam Laundry and washrooms n Toilets and showers n Washing machine Factory n Equipment washing n Water added to product Shop and canteen n Toilets and sinks n Dishwasher Water in the product Domestic wastewater/ trade effluent 2 Fig 2 Block representation of water inputs and outputs for an example site

7 The main benefits of using a water balance to identify and implement opportunities to reduce water use are: reductions in: - water supply costs; - on-site water treatment costs; - on-site effluent treatment costs, including chemicals and capital depreciation; - effluent and sewage disposal costs; - wasted raw materials or products; - management and handling costs, eg pumping, maintenance and heating; improved compliance with current and future environmental regulations; better relationships with regulators, employees, the general public and the local community; improved environmental management; greater employee awareness of environmental issues and the importance of waste minimisation to the company. 1 Remember: If you don t measure it, you can t manage it. 1.3 HOW TO USE THIS GUIDE This Guide explains how to draw up a water balance for your site and then use it to save money by reducing water use. For small to medium-sized sites, this involves following the simple step-by-step procedure described in Section 2. Section 3 extends this procedure to cater for larger, more complex sites. In the Guide, the term domestic wastewater is used for domestic water and sewage discharged at the lower domestic sewage rate. Trade effluent refers to effluents from industrial processes on which higher charges are levied by sewage treatment works. The step-by-step approach to reducing water use described in this Guide involves: 1 Obtaining commitment and resources 2 A preliminary review 3 Drawing the picture 4 Adding the detail 5 Using the water balance to save money 6 Continuous improvement You may want to use this Guide to help drive forward a water saving campaign. Drawing up a water balance for your site forms the detail of a typical water saving campaign (see Fig 3 overleaf). This process is broadly similar for both industrial and commercial sites. Examples of water use in business are given in Appendix 1. To assist in implementing water savings, Good Practice Guide (GG26) Saving Money Through Waste Minimisation: Reducing Water Use 2 describes a systematic approach. Good Practice Guide (GG67) Cost-effective Water Saving Devices and Practices 2 describes a variety of water saving measures for industrial and commercial sites and gives advice on how to identify the most appropriate water saving devices and practices for specific equipment, processes or sites. 2 Available free of charge through the Environment and Energy Helpline on freephone

8 1 PHASE 1 - Initiation Obtain commitment from senior management. Involve staff and appoint the leader (Champion) of the water saving team. Find out about water saving devices and their application, eg contact the Environment and Energy Helpline on for advice. Talk to other interested people in the organisation. Develop a simple programme. Allocate sufficient resources. PHASE 2 - Water use survey and development of the water balance Identify where, how and why water is used. Identify the water quality requirement at each point of use. Determine the water quality and availability at each point of discharge. PHASE 3 - Evaluation of water saving options Evaluate current and future water costs by area or item of equipment. Identify and evaluate cost-effective water saving devices and practices. Carry out trials of likely options. PHASE 4 - Implementation Train staff (if necessary). Implement cost-effective water saving devices and practices. Monitor the implemented devices and practices. Communicate successes and savings to employees. Obtain feedback from employees. Fig 3 The four phases of a typical water saving campaign Wholesale food distributor saves money at over 100 sites Booker Belmont Wholesale Ltd fitted simple water saving devices at 109 of its cash & carry wholesale outlets in the UK. For an average cost of around 675/site, water use and wastewater production were reduced by 65% overall. Each site saved on average around 980/year, giving a total reduction of /year. For more details, see Good Practice Case Study (GC61) Low-cost Measures Save Water at Multi-site Company. 3 Nearly 1% of turnover saved by recycling process effluent Hodgson Chemicals Ltd, a Humberside company employing 180 people, investigated cost saving opportunities while seeking the improvements in environmental performance needed to achieve authorisation under Integrated Pollution Control (IPC). Investment of in new pipework and tanks allowed a liquid waste stream to be recycled. This has enabled the Company to save /year in effluent charges and /year in recovered product. For more details, see Case History (CH66) Cost Savings Through Improved Waste Management Available free of charge through the Environment and Energy Helpline on freephone

9 2 A SIX-STEP PROCEDURE FOR CONSTRUCTING/USING A WATER BALANCE Use the simple six-step procedure described below to construct a water balance for your business. Then use your water balance to identify opportunities to make significant cost savings by reducing water use and wastewater/effluent generation. If you need further advice on any aspect of the procedure, contact the Environment and Energy Helpline on freephone STEP 1 - OBTAINING TOP-LEVEL COMMITMENT AND ASSESSING RESOURCES REQUIRED Obtaining top-level commitment As with any waste minimisation programme, commitment from senior management is vital for success. This should be obtained at an early stage particularly if you do not have the necessary authority to commit resources to produce a detailed water balance or to investigate and implement water saving opportunities. It may be easier to obtain top-level commitment once you have started to develop your water balance and are in a position to: highlight current costs; identify the need for more information; suggest the scope for potential savings. Your chances of success will be significantly improved if you can also suggest some no-cost and lowcost water saving measures, together with the anticipated costs and savings. Examples from other companies may be appropriate, but specific potential projects for your site will carry more weight. Examples might include passive infrared (PIR) controls in the men s toilets or the use of trigger hoses for washing company cars and equipment. Use this Guide and Good Practice Guide (GG67) Costeffective Water Saving Devices and Practices 4 to help you identify fruitful ideas for potential projects Assessing staff and resources required The time and effort needed to produce a water balance depends on your site. On a simple site, it could take only a few hours. On a more complicated site, it could take up to two days. Allocation of resources depends on the scale of the process or the area to be investigated, eg one person working part-time or a mixed team of engineering, production and environmental staff. Some companies have successfully employed students on work placements to gather data. Do not forget to assess the resources needed for sampling (if necessary) and ongoing monitoring work. Work experience student helps brewery save money J W Lees & Co (Brewers) Ltd employed a graduate trainee to map the water system, supervise the installation of new water meters for each main production/office area and monitor subsequent consumption. The waste minimisation initiative led to water saving measures and cost savings of nearly /year. For more details, see Good Practice Case Study (GC41) Family Brewery Makes Big Water Savings. 4 4 Available free of charge through the Environment and Energy Helpline on freephone

10 2.2 STEP 2 - PRELIMINARY REVIEW Your preliminary review should consist of: gathering existing data, eg annual water use and costs; a brief assessment of the major gaps in your information; deciding how detailed a water balance is appropriate for your company. 2 Walk round your site or building. Use a note pad to make sketches and notes on water-using activities and operations. Tell other people what you are doing and ask them for their views on water use and current practices. Your tour of the site and the information you obtain may highlight some fast start projects that will help you to secure top-level commitment Gather existing data Table 1 provides a checklist of the type of information you will need to produce a water balance. First collect together relevant information which already exists within the company. Check whether the information appears accurate and consistent. For example, check the meter readings on your latest water bill and find out when your water meter(s) was last calibrated. Type of data Water supply and treatment costs Water treatment Water and effluent quantities Water and effluent quality Effluent treatment costs Effluent discharge costs Effluent removed off-site in tankers Site plans Details of process or unit operation Description Water supply bills Abstraction licence fee Pumping, chemicals, operating, maintenance and labour costs System type and capacity Meter readings in and out of site, on individual machines/process areas Data on rainfall or groundwater inputs Analysis of on-site water treatment and effluent samples (either inhouse, by external laboratories or by water company) Equipment specifications from suppliers Include pumping, chemicals, operating, maintenance and labour costs Trade effluent and sewage bills Charges for discharge to controlled waters Waste disposal contractor s bills for transport, treatment and disposal Quantities and quality of tankered liquids Water distribution and drainage plans, including water sources and location of meters Process flow and pipe/process technical drawings, including manufacturers specifications Table 1 Useful existing data To reduce the risk of errors in your calculations, use the same units for water use, eg litres or m 3, depending on the size of your flows. Water Volume Conversion 5 1 m 3 = litres = 220 gallons. 1 gallon = m See Good Practice Guide (GG67) Cost-effective Water Saving Devices and Practices for other conversion factors.

11 2.2.2 Are there major gaps in your knowledge? In your preliminary review, aim to account for at least 80% of the water you pay for - including any major leaks. Examine your data and decide whether your overview of water use and costs is adequate or whether there are major gaps. If more information is needed, it is likely to be in specific areas. Investigating your few, main uses of water is likely to provide most of the cost-saving opportunities. Begin to develop a picture of your business - along the lines of Fig 1 (see Section 1) - as soon as possible. This will help you to identify gaps in available information and to focus your efforts. You will develop the picture and add detail during Steps 3 and 4 (see Sections 2.3 and 2.4). You may prefer to leave the decision on what extra information and measurements you need until you have produced your first water balance diagram, ie the equivalent of Fig 2 complete with numerical data. You will achieve this in Steps 3 and 4 (see Sections 2.3 and 2.4) How detailed a water balance should you produce? A simple water balance covering the few largest water-using activities may be sufficient to control and reduce major uses of water and related resources. You need to decide how detailed a water balance is likely to be cost-effective for your company. How far to go is a matter of judgement, about which general advice is given below. You may also wish, at this stage, to define the scope of future work, eg whether to analyse the whole site or to consider one area in more detail. To decide how detailed your water balance should be, consider the potential benefits versus the cost. What is the likelihood of identifying cost-effective opportunities to save water? How much money could you save? How much will it cost to investigate water use in more detail? For sites with significant water consumption, the potential savings will be more than sufficient to justify drawing up a detailed water balance. For example, a soap manufacturer used a water balance to identify major sources of waste and achieved savings of /year. Water balance leads to halving of mains water consumption A systematic approach was used at a soap manufacturer in Salford to identify and quantify water use and then implement measures to reduce mains water consumption. A detailed water survey revealed how and where water was being used. A water balance was then prepared using data obtained from existing invoices and meters. A 50% reduction in mains water use, worth /year, was achieved between 1992 and 1995 through a combination of good housekeeping measures and plant modifications. For more details, see Industry Example 4 Site Water Savings at a Soap Manufacturer in Good Practice Guide (GG26) Saving Money Through Waste Minimisation: Reducing Water Use. 6 For sites that have relatively low water use, an alternative criterion for deciding whether a detailed water balance should be produced is the size of annual water and effluent bills. For example, Booker Belmont Wholesale Ltd decided not to investigate water saving opportunities at sites where water and effluent bills were less than 300/year. However, the installation of simple, water saving devices at over two-thirds of its sites produced significant overall cost savings. 6 Available free of charge through the Environment and Energy Helpline on freephone

12 Low-cost measures save water at multi-site company Water is used at Booker Belmont Wholesale Ltd s cash & carry depots in a number of areas including washrooms, canteens, butcheries and toilets. In 1994, Head Office implemented a water saving initiative as part of an environmental improvement programme. Percussion (push) taps, toilet cistern volume adjusters and flushing controls were fitted in 109 of Booker s 160 cash & carry wholesale outlets, achieving net savings of in the first year and /year thereafter. 2 For more details, see Good Practice Case Study (GC61) Low-cost Measures Save Water at Multisite Company. 7 Estimating potential savings Cost savings can arise from reductions in: water use, eg in domestic or process use; on-site water pumping and associated maintenance; water treatment, eg lower chemical costs and filter backwash; water heating or cooling requirements; effluent pumping; effluent treatment; effluent discharge. As a general rule-of-thumb: If no water saving measures have so far been implemented, savings could be 50% or more of your water-related costs. If you have implemented some water saving projects but not applied a systematic approach, the potential savings could be at least 20% of your water-related costs. Do not forget the possibility of reducing the amount of raw materials and product lost in effluent. This can be significant in some cases, eg see Case History (CH66) 7 at Hodgson Chemicals. Environmental review identifies product losses in effluent In 1993, effluent charges rose sharply at a chemicals Company, which employs 45 people at its plant in North Wales. An environmental review revealed that total effluent costs were /year and not 4 000/year as previously thought. The review also showed that, as well as paying extra trade effluent charges, the Company was losing saleable product in the effluent. Following improvements and procedural changes, the Company reduced its effluent charges by 3 000/year and saved 8 500/year through product recovery from the effluent. For more details, see Good Practice Case Study (GC20) Environmental Review Helps Raise Profits. 7 Many people use at least twice as much water than is needed to perform a given task, eg washing down a piece of equipment with a continuously running hose. Typical reductions in water use for various projects are shown in Table 2. 7 Available free of charge through the Environment and Energy Helpline on freephone

13 Water saving initiative Per project Typical reduction Per site Commercial applications Toilets, men s toilets, showers and taps 40% (combined) Industrial applications Closed loop recycle 90% Closed loop recycle with treatment 60% Automatic shutoff 15% Countercurrent rinsing 40% Spray/jet upgrades 20% Re-use of wash water 50% Scrapers 30% Cleaning-in-place (CIP) 60% Pressure reduction Variable Cooling tower heat load reduction Variable 2 Deciding your budget Table 2 Typical achievable reductions in water use Once you have estimated the potential savings, use your company s method for new project appraisal to determine how much money might be available to obtain missing information and/or construct a water balance. Identification of the maximum project budget can help determine the areas on which to concentrate. This helps to assess and eliminate projects that are unlikely to be cost-effective. Maximum Project Budget ( ) = Calculated saving ( /year) x Required payback period (years) The maximum project budget concept is explained - with the aid of an example - in Good Practice Guide (GG67) Cost-effective Water Saving Devices and Practices. 8 This Guide also gives advice on how to identify project costs. 2.3 STEP 3 - DRAWING THE PICTURE Produce a picture representation of your site For any water balance, the first step is to produce a pictorial representation of your site. All premises - whether a complex site or a single building - can be described by a series of activities or operations. Fig 1 in Section 1 shows a typical example. Identify and mark on your picture: major uses of water; the location of on-site water meters (there is usually one on the mains supply entering a site); the points at which domestic wastewater and/or trade effluent enter the site drainage system. For more complex sites, use a site plan and process flow diagrams to help you produce a picture representation of the site. 8 Available free of charge through the Environment and Energy Helpline on freephone

14 When drawing your picture, remember that: you are looking for major water-using activities as part of an operation, process or a piece of equipment where: - water enters; - a function occurs; - water or effluent leaves; inputs and outputs may be in a different form, eg liquid raw materials, steam and product. To help you, two examples of water-using activities are shown in Fig 4. 2 Define major water-using operations by the type of activity carried out, eg cooking or drying. Alternatively, designate activity areas according to boundaries where flows can be measured easily. If a water-using operation becomes unmanageable, try splitting it into smaller units. Detergent Evaporation Evaporation, spray and mist to atmosphere Cooling tower Water Water Pump Washing machine Clothes dryer Cold well Effluent to sewer Blowdown to sewer Leaks and overflows Process cooling (a) Key Unit operation Inputs (b) Water meter Outputs Fig 4 Unit operations (a) a laundry (b) a cooling tower Draw a block diagram Now translate your picture into a more manageable form by drawing a block diagram that indicates the relationships between operations. Fig 5 shows the block representation of Fig 1. The major water-using activities are the laundry/washrooms, the factory and the shop/canteen. Each major activity on the site is represented by a box, which lists the significant water uses. Water feeding to the different activities is represented on the diagram by arrows connecting the relevant boxes. Standard practice is to show water inputs at the top and water outputs at the bottom of the diagram. All water, including the mains water supply, should also be shown. 10

15 Mains water Meter Liquid raw materials Evaporation and steam Laundry and washrooms n Toilets and showers n Washing machine Factory n Equipment washing n Water added to product Shop and canteen n Toilets and sinks n Dishwasher 2 Water in the product Domestic wastewater/ trade effluent Fig 5 Block representation of a simple example site Add data to the diagram to produce an initial water balance To produce the water balance, the amounts of all major water and effluent flows are added to the block diagram. The units used should be consistent and are typically m 3 /day. Numerical values for water/effluent flows are obtained from investigations and measurements (see Section 2.4). The aim is to obtain as complete an account as possible of where the water is going on the site. Use the information gathered in your preliminary review to begin to construct a water balance for your site. If necessary, use a site plan and process flow diagrams to help you. Add the information you can, but at this stage you may not be able to account for a significant proportion of your water use. In Step 4 you will add detail to your water balance by carrying out more investigations and measuring flows. Fig 6 shows an initial water balance for the example company depicted in Fig 5. In addition to the main water inputs and wastewater/effluent outputs, flows such as liquid raw materials used in the factory and steam released from the factory have been identified. The completed water balance for this site is shown in Fig 14 (see Section 2.4.7). As an example of a non-industrial site, a detailed water balance exercise for a medium-sized hotel follows after Fig 6. 11

16 Mains water Meter m 3 /day 2 Laundry and washrooms n Toilets and showers n Washing machine 1 m 3 /day liquid raw materials 75 m 3 /day?? Factory n Equipment washing n Water added to product Evaporation and steam? Shop and canteen n Toilets and sinks n Dishwasher? 65 m 3 /day? 5 m 3 /day in the product 79 m 3 /day domestic wastewater/ trade effluent Total 84 m 3 /day Key? To be assessed Fig 6 Initial water balance for a simple example site Constructing a water balance for a medium-sized hotel One of the hotels in a chain has high water and sewage charges. These jumped from 6 325/year in 1995/96 to /year in 1996/97. The hotel, which is supplied with water only from the mains, has 30 bedrooms, with a restaurant and bar (open to non-residents). Ten of the rooms are in a separate new wing. All the bedrooms are equipped with bath, shower and WC. Other facilities include a swimming pool and leisure facilities. The hotel also has its own kitchens equipped with two large dishwashers and separate laundry facilities with two washing machines. Outside there are extensive gardens. In addition to the water company s meter, there are sub-meters on the old bedroom complex (fed by an independent pipeline off the incoming water main), on the kitchens and on the pipeline serving the swimming pool, leisure facilities and new bedroom complex. The hotel had a 60% occupancy rate during 1996/97. The gardens were only watered on two afternoons in July using a hose fed off the mains supplying the bar and toilets. Because some laundry is charged to clients, a record is kept of machine use. The larger (50 lb wash) was used 231 times during the last year and the other (12 lb wash) was used 450 times. Machine specifications show that the larger machine uses 112 litres/fill and each wash cycle takes five fills. The smaller machine takes 60 litres/fill and seven fills. The sub-meters on the kitchens show that 248 m 3 was used during 1996/97. The first step is to draw a block representation of the hotel and fill in available data for the year. The first values to be entered are those from the sub-meters, ie: 298 m 3 for the old bedroom complex; m 3 for the flow to the swimming pool, leisure complex and new bedroom wing; and 248 m 3 for the kitchens. 12

17 The next step is to do some calculations to determine other flows. At 1.34/m 3, a bill of gives a water input from the mains supply of m 3 /year. In the laundry, the large machine used (231 x 112 x 5)/1 000 = 129 m 3 /year and the small machine used (450 x 60 x 7)/1 000 = 189 m 3 /year - a total of 318 m 3 /year. The average water consumption of an occupied bedroom is approximately 68 litres/day. A crosscheck shows that the metered water use for the old bedroom complex agrees with the value calculated from the occupancy rate and assumed average water use, ie (20 x 68 x 365 x 0.6)/1 000 = 298 m 3 /year. Assuming the two sets of bedrooms use water at the same rate, then water use for the ten-bedroom wing is 149 m 3 /year. In the garden, one hose was used for two afternoons in July - say for four hours. A garden hose uses 8.3 litres/minute as a minimum. The water use is estimated at (2 x 8.3 x 4 x 60)/1 000 = 4.0 m 3 /year. No data exist for the restaurant and bar. It is estimated that two sinks with a maximum of two taps run for 6 hours/day for 5 days/week. Assuming that the taps run at the same rate as the hose, a reasonable guessestimate is (2 x 8.3 x 60 x 6 x 5 x 52)/1 000 = m 3 /year. 2 Fig 7 shows the water balance for the hotel. The total water consumption by the various areas of the hotel is therefore ( ) = m 3 /year. This compares favourably with the value calculated from the previous year s bill of m 3 /year. Hotel management have now proved that water use in 1996/97 was excessive. Meter m 3 /year 1554 m 3 /year Restaurant/bar Sub-meter 298 m 3 /year 20-bed accommodation 149 m 3 /year 10-bedroom wing Sub-meter m 3 /year Sub-meter 248 m 3 /year Swimming pool Leisure facilities Kitchens Known Calculated Estimated 318 m 3 /year Laundry 4 m 3 /year Gardens Fig 7 Water balance for the hotel Steps which the hotel could take to investigate its water use include: checking the accuracy of the incoming water meter; turning off all water-using devices and then observing the meters and checking the drains for any flow (but not the drains that also receive rainwater); fitting more sub-meters to obtain more accurate data; looking for leaks; examining water use in the swimming pool and leisure facilities; checking comparative occupancy rates between the new and old bedroom complexes. 13

18 2.4 STEP 4 - ADDING THE DETAIL In this step, you add detail to your initial water balance by: working out which activities/processes are likely to use the most water under both normal and abnormal operating conditions; measuring flows to add information to your water balance; continuing to account for more and more of your total water input until you decide that it is no longer cost-effective to make new measurements. 2 Your preliminary review (see Section 2.2) may have enabled you to account for 80% or less of the site s water use when you drew up your initial water balance. Depending on the amount of water you use, it may be cost-effective to make measurements to identify 95% or more of your water use. This issue should have already been considered as part of your preliminary review Identify water supplies Table 3 lists the main water sources used by UK companies. In most modern buildings, water from the mains and any abstracted water is kept separate from rainwater. When looking at water sources, examine the potential for crossover between these water systems. Some companies collect and treat rainwater for use within their processes. Type Mains Surface water abstraction Groundwater abstraction Rainwater collection Supply route Metered flow via a water company pipe Extracted from a river, stream, lake, reservoir or canal Pumped from borehole(s) From a storage tank Table 3 Main sources of water To help identify where water is used and which activities/processes use the most water, start by finding out about where your water comes from and how it is treated and distributed on-site. How is water supplied to the site, eg mains, river, reservoir and/or borehole? Is water stored on-site, eg in tanks or lagoons, and what is the storage capacity? Is water treated on-site and if so, how? How is water transferred, eg by pump, gravity or manually? Fig 8 shows an example assessment of site water sources. The next stage is to measure flows (see Section 2.4.5). Source Processes/ areas served Treatment Storage (type and capacity) Transfer method Use and frequency Quantity (m 3 /day) Mains Product None None Pumped Production To be hours investigate Borehole Product Softening Tank (5 m 3 ) Pumped Downtime of To be mains pumpsinvestigate (5 days/year) River Gardens None None Pumped Summer and gravity To be investigate Fig 8 Example water sources assessment 14

19 Look at your water and effluent bills to get a feel for the quantities of water used and the amount of effluent discharged from the site/area. If possible, focus on large flows first Investigate water use Depending how complex your site is, use one or more of the following approaches to identify and investigate major uses of water. Walk around the site/process looking at everything to find water-using items/points. Identify the location of water meters and discuss with staff where water is used. Trace water supply pipes from sources to water use points, if visible. Obtain drawings of water supply system. 2 At the same time, make a note of effluent sources and trace pipework back to water supplies. This will save you time and effort later. The identification of effluent sources is described in more detail in Section When collecting data, also gather supporting information such as: number of employees on site or per shift; type of product being produced; number of lines operating; washing operations carried out, eg number of rinses or cycles. You may wish to develop a diagram to help you keep track of your findings. Such a diagram will be particularly useful if no plan of the water supply distribution system is available. Identify the points where water enters the site or is abstracted on-site. Trace the water supply pipes from these points to any plant/equipment that uses water. Draw a flow diagram of pipework connections. Water use survey helps wallpaper manufacturer achieve significant savings By mapping its site water services and developing a water balance, a wallpaper manufacturer has reduced water consumption at its Lancashire site by nearly 40%. These actions, together with recommendations from process improvement teams investigating site water use, highlighted how water was being used and where it was being wasted. Estimated savings of /year were achieved at virtually no cost. For more details, see Industry Example 6 Site Water Savings at a Wallpaper Manufacturer in Good Practice Guide (GG26) Saving Money Through Waste Minimisation: Reducing Water Use Identify sources of effluent To help you understand where effluent is generated and its fate: Obtain drawings of the effluent drainage, surface water drainage and foul sewer systems. If these are not available, it may help to develop diagrams for your site. Appendix 2 provides guidance on how to produce and use site drainage plans to identify effluent sources. 9 Available free of charge through the Environment and Energy Helpline on freephone

20 Walk round your site/process finding out where water goes and looking for sources of effluent. Make a note of your observations. Talk to other people about where effluent is produced. Locate any effluent meters or sampling points. As well as discharges to sewer or watercourses, find out about liquid wastes and slurries removed off-site in tankers. 2 The list of typical effluent sources in Table 4 below is intended to help you identify all your effluent sources and water losses. Effluent sources/water losses General Water treatment units Water storage, including boiler system Storm/surface water run-off Groundwater Firewater systems Car park Fuelling depot Refrigeration units Laboratories Drying processes Hot processes Oil interceptors Storage tanks Site cleaning Commercial Laundry Kitchens Toilets/bathrooms/wash block Swimming pool and leisure facilities Boiler/heating systems/air conditioning Gardens and water features Vehicle washing Industrial Cooling tower Steam system Condensate recovery Condensate Process/production Scrubbers/strippers Safety showers Effluent treatment plant Examples Filter backwash, wet sludges, chemical spillages, ion exchange regeneration, reverse osmosis effluents Leaks and overflows Additions to effluent drains Infiltration to effluent drains Leaks, unnecessary use, wrong connections, safety/pump testing Vehicle washing wastewater Spilt fuel and oils to drain Condensate Condensate, cooling water, liquid effluents, mains water vacuum pumps Evaporation Steam, condensate Water/effluent removal Bund water/effluent drainage, tank overflows, delivery pump/shaft seal leaks Hoses Effluent, steam, evaporation from dryers Effluent, steam, liquid wastes Effluent, steam Wash block effluent, swimming pool water Blowdown, condensate, steam Excess water run-off, overflows Effluent, detergents Blowdown, evaporation, spray/mist Steam leaks and relief valve discharges, steam trap condensate, steam and evaporation, boiler scale and sludge, blowdown Vent losses to atmosphere, leaks and overflows Loss to product, loss to drain (excluding recovery) Evaporation, water in product Overflows, mist/vapour Leaks, unnecessary use Treated effluent, sludge, aerosols, liquid wastes, eg reverse osmosis concentrate 16 Table 4 Typical effluent sources and water losses

21 Domestic wastewater usually goes down a foul sewer for treatment by your local water company or authority. Uncontaminated rainwater should preferably be discharged to a soakaway or to a surface water drain. To avoid unnecessary treatment charges: Other water losses check that rainwater is not entering the foul sewer; keep domestic sewage and surface water drainage separate from trade effluent; label or colour-code all drains - make sure that staff are aware of the difference. To complete your water balance, you need to consider other ways in which water is lost from your site/process. For example, water may leave the site in product, eg soft drinks manufacture, or as steam, eg some food processing uses large quantities of steam. Without information about these other losses, it will be difficult to complete a water balance for your site. 2 Remember to check for water losses in: products and by-products; emissions to atmosphere, eg evaporation, steam, mist, spray and losses from pressure relief valves; slurry and sludge wastes; spillages, leaks and overflows; cooling water, including once-through; hoses and taps left on; leaks from underground tanks or pipes Quantify water use and effluent flows Once you have identified all major water uses and effluent sources, the next stage is to order them from largest to smallest. Do this through a combination of common sense, your own knowledge and discussions with other people. Starting with the largest anticipated water use/flow, find out how much water is used each time and how often water is used, either by using a meter or timed water flow into a container of known volume. Starting with the largest effluent source, find out how much effluent is generated each time and how often effluent is generated. The effluent flow may be the same as the flow of water used. There are a number of things you can do to help you quantify flows. In order of preference, these are: measure directly; calculate from other measurements; calculate from manufacturers published information; calculate from typical use information; estimate. 17

22 Direct measurement The direct measurement technique described below involves performing a spot check on the flow from a piece of equipment or process using a bucket or another container and a stopwatch (or a wristwatch with a second hand). The flow rate can be calculated from the volume of water/effluent collected over a known time. You may need to undo a pipe connection temporarily to allow water/effluent to flow into your container. This technique will not be applicable to all flows. Method 2 Assess health and safety requirements, eg use gloves and safety glasses. Assemble equipment, eg bucket, watch, notepad, pen and rope for lowering bucket into drain. Find a measuring point where it is possible to catch all the flow in the bucket. Position the empty bucket and start the stopwatch (or note the exact time) immediately the bucket starts to catch the flow. Remove bucket, stop the watch and note the time when the bucket is nearly full (but not overflowing). Measure the contents of the bucket in litres using either graduations on the bucket or a measuring cylinder. Calculate the flow rate in litres/second by dividing the volume of effluent collected in litres by the number of seconds over which collection took place. Alternatively, calculate the flow based on the weight of the effluent and assuming the effluent has the density of water, ie 1 kg of effluent occupies 1 litre. Measure the flow at representative times, including both continuous and intermittent discharges. As this is a one-off measurement, repeat the test to determine variations in flows or average flow rates. If direct measurement is not practicable, consider: Obtaining data from manufacturers brochures, eg water use for washing machines. Take care to use data for the exact model and note any modifications. If possible, compare these data with actual water use. Savings are possible if the unit is operating at above its recommended consumption. Estimate water use from knowledge of the process. For example, for a tank filled each time for a pre-rinse and a wash, measure the tank dimensions and calculate the volume of water used. Allow for partial filling or overflows. Take measurements to cover all operations affecting water or effluent quantities. In particular, check intermittent activities, eg cleaning, where water use is often variable and wasteful. More information about measuring water use and flow is given in Good Practice Guide (GG67) Cost-effective Water Saving Devices and Practices. 10 Monitoring washing/cleaning operations Monitor washing and cleaning operations by estimating/counting hose or tap use, eg how frequent and how long at what flow rate, and calculate water/effluent quantities. Fig 9 shows an example calculation of water use by a hose. The same calculation can be applied to effluent generation Available free of charge through the Environment and Energy Helpline on freephone

23 Item Hose Instantaneous flow/average flow rate A Measured 0.5 litres/second = litres/hour Length of event B Measured 2 hours Amount/event C A x B litres Frequency of event D Measured 2/day Daily total E C x D litres/day Daily flow E/ m 3 /day Estimating non-process uses Fig 9 Example calculation of water use If you have combined domestic and effluent sewers, you may need to estimate domestic sewage quantities. Typical values for domestic water consumption are shown in Table 5. 2 Item Toilets Sinks Showers Baths Dishwasher Laundry (washing machine) Vehicle washing Garden hose Residential occupant Employee (full-time, no canteen) Employee (full-time, with canteen) Average water use litres/flush 3-6 litres/event litres/event (higher use for power showers) litres/event litres/event litres/event Ranges from 100 litres/vehicle using buckets up to 900 litres/vehicle using a hose litres/hour, ie litres/minute 140 litres/day/person 25 litres/day/person 40 litres/day/person Record your information Table 5 Typical rates of domestic water use When tracking water use, it is important to keep accurate records of your findings for future use. As a water use chart These simple block diagrams will help you to determine flows for your water balance. Figs 10 and 11 show example water use charts for a commercial and an industrial site respectively, where submetering is present in the industrial case. Location: Unit operation: Hotel Laundry Date: 21/3/99 Time: hrs Investigator: M Brown Source: Mains water Metered/unmetered Use 1: Washing machine Volume: 2.4 m 3 /day Use 2: Sink Volume: 0.24 m 3 /day Fig 10 Water use chart: commercial example 19

24 Location: Unit operation: Brewery Cooling tower Date: 21/3/99 Time: hrs Investigator: D White Source: Mains water Metered/unmetered 2 Use 1: Make-up water Volume: 7 m 3 /day Use 2: Hose Volume: 5.4 m 3 /day On a worksheet Fig 11 Water use chart: industrial example Entering quantity and cost data on a worksheet will help you use the water balance to identify and prioritise water saving opportunities (see Section 2.5). Remember to keep units consistent and choose the time period that is most convenient for you. The example worksheets shown in Figs 12 and 13 are based on weekly use. Fig 12 shows an example worksheet for a fictitious commercial site (the same site used to produce the water use chart shown in Fig 10). In Fig 12, the number of times the sinks are used is calculated on the basis of three employees, each washing eight times a day for five days/week. The calculations assume negligible use of liquid detergent/fabric softener and negligible water losses as steam/evaporation. Fig 13 shows an example worksheet for a fictitious industrial site (the same site used to produce the water use chart shown in Fig 11). In Fig 13, the amount of evaporation is calculated from the volume of make-up water minus the volume of blowdown and assuming no leaks and/or overflows. Hose use assumes a flow rate of 0.5 litres/second, giving 1.8 m 3 /hour of use. Use occurs for 3 hours/day and 5 days/week, ie 15 events/week. Appendix 3 contains a template worksheet for you to photocopy and use to calculate quantities and costs for water use and effluent discharge. A copy of this template is also provided in the pocket in the back cover of this Guide. 20

25 Date: 21/3/99 M. Brown Review carried out by: Time: Hotel Review carried out by: Water supply costs: 70 pence/m 3 average 50 pence/m 3 (including volume and pollution load charges) Effluent discharge costs: Water Effluent Cost of output ( /week) Total output (m 3 /week) No. of events in a week* Output/event (m 3 ) Cost of input ( /week) Total input (m 3 /week) No. of events in a week* Process Input/event (m 3 ) Dept Laundry Washing machine Sinks Total * NB Use the time period appropriate for your site Fig 12 Calculating the weekly cost of water use and effluent generation: example commercial site 2 21

26 2 Date: 21/3/99 D. White Review carried out by: Time: Brewery Review carried out by: Water supply costs: 70 pence/m 3 assuming an average 50 pence/m 3 (including volume and pollution load charges) for hose use with moderate pollution assuming 30 pence/m 3 for blowdown (based on volume charges only) Effluent discharge costs: Water Effluent Cost of output ( /week) Total output (m 3 /week) No. of events in a week* Output/event (m 3 ) Cost of input ( /week) Total input (m 3 /week) No. of events in a week* Process Input/event (m 3 ) Dept Cooling tower Water make-up Hose 1.8 (per hour) Evaporation/ spray Blowdown Total * NB Use the time period appropriate for your site Fig 13 Calculating the weekly cost of water use and effluent generation: example industrial site 22

27 2.4.7 The water balance Adding the information obtained from your investigations of water use and effluent generation to your block diagram should enable you to complete your water balance. In some cases, it may now be easier to expand the diagram by dividing a block into two or more activities. The water balance should be a schematic representation of your process showing: all known points of water flowing into the process; all known points of water flowing out of the process, as effluent, liquid waste, product or evaporative loss (see Appendix 5 for steam); the amounts of these flows (in consistent units). In theory, the total of all the inputs should equal the total of all the outputs for either individual unit operations or the whole process. However, this is rarely the case in practice. Your initial aim should be an accuracy of ±10% on the total amount of water you can account for. 2 Fig 14 shows the completed water balance for our example company from Step 3 (see Section 2.3). The company has now produced data for all flows and identified major water leaks from the factory. In this example, 84 m 3 /day out of the input of 85 m 3 /day of water has now been accounted for. Mains water Meter m 3 /day 5 m 3 /day 75 m 3 /day 4 m 3 /day 1 m 3 /day liquid raw materials 1 m 3 /day evaporation and steam Laundry and washrooms n Toilets and showers n Washing machine Factory n Equipment washing n Water added to product Shop and canteen n Toilets and sinks n Dishwasher 65 m 3 /day 5 m 3 /day Leaks 5 m 3 /day 4 m 3 /day 5 m 3 /day in the product 79 m 3 /day domestic wastewater/ trade effluent Total 84 m 3 /day Fig 14 Completed water balance for a simple example site Additional example water balances for a hotel and an industrial site are shown in Appendix 4. 23