Water minimisation in the food and drink industry GG349

Transcription

1 Water minimisation in the food and drink industry GG349

2 Water minimisation in the food and drink industry

3 Envirowise 2

4 Contents Introduction 5 Managing water use 7 Measuring water use and flow 9 Process water use 13 Process control 19 Product recovery techniques 27 Cleaning 31 Ancillary water use 37 Further information 41

5 Envirowise 4

6 Introduction All industrial and commercial organisations use water. Many organisations take water for granted and often do not know how much they are using, or that the amount they are paying for their water supply and effluent disposal could be reduced. Sites that have not previously tried to save water can usually achieve 20% savings on water and effluent bills right away at little or no cost. Savings of 40% or more may be possible with longer-term water saving projects. This is especially true for industrial applications, where large quantities of water are used. However, it is important not to forget commercial and ancillary water uses, as every saving counts. The food and drink industry is no exception. This easy-to-use Guide describes how businesses in all sectors of the food and drink industry can take steps to minimise their water use without compromising their processes or hygiene standards. Taking measures such as those described in this guide will also help food and drink processing companies to comply with the provisions set out in the Integrated Pollution Prevention and Control (IPPC) Directive. Why should you reduce the amount of water you use? The costs of water supply and effluent discharge have risen considerably in the last decade, and are likely to continue to do so as water companies seek to meet the costs of complying with European Directives such as the Urban Waste Water Treatment Directive (UWWTD). Reducing the amount of water you use will save you money in water supply charges. In most cases, it will also have the effect of reducing the volume of effluent your organisation discharges, which will cut your trade effluent charges. You will be reducing your company s impact on the environment as well as saving money. Think also about the hidden costs associated with water use; the energy you could be saving, for example, by reduced pumping of water or having to heat less water. There may be other benefits too. Some of the water saving measures described in this Guide will also enable you to recover some of the raw material or product from your process or cleaning chemicals, which previously may have been lost in the effluent stream. This will have the added benefit of lowering effluent strength, which will reduce your trade effluent charges further. How to use this Guide There are eight Sections in this Guide. Process water use, Cleaning and Ancillary water use describe water saving ideas for the main areas of water use in your organisation. Process control describes the technologies available to automate water saving practices. Measuring water use and flow and Managing water use suggest how you can take control of water usage, from measurement of water usage to encouraging a water-saving culture in your organisation. Product recovery techniques describes the technologies available to recover product from effluent streams at the same time as saving water. Water saving practices or technologies are divided into no cost, low cost and more ideas to help you decide what is best for your situation. Suggestions in the more ideas category are things that may need some planning, or are more expensive to implement. No cost: actions you can take now Low cost: low-cost actions More ideas: actions you need to plan Further information lists useful Envirowise publications, as well as the Environment and Energy Helpline number where you can get free advice. For more detailed information on the subjects covered by this Guide, you can visit the water minimisation web site water_minimisation Envirowise Introduction 5

7 Envirowise Introduction 6

8 Managing water use This Section looks at how to manage water use within your company, from initial investigations and commitment from senior management, through to implementation and continuous improvement. Companies that adopt a systematic approach to water reduction typically achieve a 20 50% decrease in the amount of water used. All this information and more is on our website at It is vital to have effective procedures in place to manage water minimisation, otherwise any improvement may become a one-off purge with no follow-up; employees are not motivated to continue good practices and the programme will lose momentum and fail. Successful management involves not only identifying and initiating water saving projects, but continual monitoring of water use and company/staff practices, and a timely, appropriate response to the information gathered. This Section identifies the key issues and actions involved in managing water use successfully. Visit the Managing water use section of the water minimisation web site, and go to Ongoing management for more information. All the steps outlined in this Section are no- or low-cost activities. Managing water

9 Envirowise Managing water use 8 Managing water use Steps Guidance 1 Obtain management commitment to water saving activities 2 Measure water use on your site 3 Analyse results and identify areas of potential savings Your business is most likely to make savings if there is a commitment to improving at management level. It may be easier to obtain top-level commitment once you have gathered some initial information on current costs and potential savings. It is also useful to have someone in the company who will champion water saving initiatives. Create a water balance (see Measuring water use and flow on page 9). This will help you to decide on the scope of activity (whole site or one area). Brainstorm and research ideas for reducing water use in certain areas. Involve staff at this point as they may have good ideas. Identify potential projects, and the potential cost savings. 4 Set targets Decide on your maximum budget. Set targets for the savings you want to achieve in each area. Set target payback times so that you have a timeframe in which to achieve the savings. 5 Plan Get detailed costs from suppliers for any new equipment you want to install and work out what resources you need for various activities. Use this information and your targets to draw up a project design with a timetable for completion. 6 Involve staff You may already have involved staff when looking for ideas for saving water. It is vital for staff to feel that they are involved, consulted and informed; this improves motivation. Appoint teams for particular projects. 7 Implement improvements This may include training staff, installing new equipment or fixing existing equipment, and informing staff about best practice procedures. 8 Monitor, report and review Once improvements have been implemented or new practices adopted, it is important to measure and monitor regularly. That way, you not only check that you are hitting your targets, but you identify any areas that need attention. Get feedback from staff and carry out regular inspections and surveys. Inform staff of progress and results, and be sure to report success stories. 9 Continue Use your reviews as the basis for further action. Aim for on-going improvement.

10 Measuring water use and flow This Section looks at how you can measure and account for the water that you use on your site. Knowing how much water you are using and where it goes are the first steps towards being able to control and reduce the amount of water you need. Companies that use this information to adopt a systematic approach to water minimisation typically achieve a 20 50% decrease in the amount of water they use. Visit the Measuring water use and flow section of the water minimisation web site, and go to Water use in food production. All this information and more is on our website at Suggested actions in this Section include carrying out a water survey to create a water balance, and considering the different options available for devices that measure quantity and flow. Regular surveys will keep water and effluent systems in order. Checks should be carried out on a monthly basis, at least until full control of water use has been established, when an annual survey may be sufficient. Surveys typically reveal leaks; incorrectly set, poorly maintained or broken equipment; unidentified connections; redundant lines; unknown or unauthorised usage or discharge and clean water discharges to effluent streams. These are all things that can be rectified quickly. Measuring water

11 Envirowise Measuring water use and flow 10 Carry out a water survey and use the information to create a water balance Water balances. A water balance is a numerical account of where water enters and leaves your site and where it is used within the business. It lists the amounts of water used by each main process. It can be kept quite simple or be made very detailed, depending on your situation and needs. The table summarises the steps you need to take to create a water balance, along with explanatory guidance for each step. Carrying out a survey will not cost you much but remember to include management and staff time. Visit the Measuring water use and flow section of the water minimisation web site, and go to Water balances for more detailed information on carrying out a survey and creating a water balance. Visit the Measuring water use and flow section of the water minimisation web site, and go to Family brewery makes big water savings for an industry example. Steps 1 Gather existing data: Water supply and treatment costs Water and effluent quantities and quality Effluent treatment costs Effluent discharge or removal costs Site plans Details of process or unit operation 2 Decide whether your data are adequate or whether you need more detail Guidance As well as water, sewage and trade effluent bills or licences, remember to include the costs of any on-site treatment (pumping, chemicals, operation, maintenance, labour). To measure water and effluent quantity use meter readings for water entering and leaving the site, and on individual process areas, if you have them. Include any data you have on rainfall or groundwater input. Remember that water may also leave your site in product, by evaporation and as steam. For water and effluent quality, use analyses of on-site water treatment and effluent samples, either in-house or by an external laboratory or water company. Ensure site plans include water distribution and drainage, water sources and meter locations. Use technical drawings of process flow and pipe/process, with manufacturer s specifications, to provide details of process operations. Aim to account for at least 80% of the water you pay for using these initial data, including any major leaks. If you need more information, it is likely to be in specific areas. Investigation of your few main uses of water is likely to provide the best cost-saving opportunities. Target areas which use the most water production processes, cleaning-in-place (CIP), utensil/container washers and hygiene systems. Weigh up the potential savings against how much it will cost you to investigate water use in more detail and how likely you are to identify cost savings. 3 Draw a diagram of your site Mark on your diagram all major uses of water, the location of all on-site water meters, and the points where domestic wastewater and/or trade effluent enter the site drainage system. Remember that inputs and outputs may be in a different form, eg liquid raw materials, steam and end-product. 4 Add data to your diagram Add the amounts of all major water and effluent flows to the relevant places on the diagram. Remember to use a consistent unit of measurement, eg m 3 /day.

12 Steps 5 Add more detail to your diagram, if needed Guidance Taking this step means you can account for a greater proportion of your water use, and with greater accuracy. You can carry out a more detailed survey of your site, to identify: where water is used and how much; which sources of water supply which processes; sources and quantities of effluent; leaks and other accidental water losses. Walking around the site, checking equipment and usage and talking to staff, often means any discrepancies in your figures can be resolved. 6 Use your completed water balance to identify cost-saving opportunities Your water balance will show you where you use the most water or generate the most effluent. Starting with these, think about why the process uses so much water or creates so much effluent, and whether action can be taken or alternative approaches considered. Envirowise Measuring water use and flow 11

13 Envirowise Measuring water use and flow 12 Use measuring devices and techniques to quantify water usage and flow This table summarises typical methods for measuring water use and flow on your site, with guidance to help you decide what is appropriate for your situation. Choosing a flow measurement device Before buying any flow measurement device consider the following: Level of accuracy required. Temperature, pressure, speed and level of contamination of the water. Condition and arrangement of pipework. Which type of meter is best for the application. Don t forget hygiene issues. Remember that accuracy of flow measurement equipment is affected by the proximity of valves, bends in the pipework and other items which affect flow. Device or technique Bucket and stopwatch Graduated bucket Water meters Turbine meters Orifice meters Application Where flows are accessible Sinks and washbasins Incoming water supply and input to specific processes In pipework carrying clean water In pipework carrying clean water Guidance Where flows are accessible, measuring the time taken to fill a bucket using a stopwatch or wristwatch with a second hand is a cheap, simple and effective way of measuring flows. Disconnect the u-bend then simulate a normal activity. The wastewater from this activity can be collected in a large graduated bucket. All sites should have a meter on their incoming water supply. This will only provide an indication of water use on the site as a whole; to measure usage effectively and target water saving practices on certain areas, consider installing a comprehensive system of meters, especially on supplies going into individual processes. Applications which use the most water production processes, CIP, utensil/container washers and hygiene systems should be metered individually. Usually provide a direct visual display of cumulative flow. These are the most commonly used and widely applicable of all water meter types. Industrial turbine meters are available in different sizes, ranging from mm in diameter, with a price range of approximately and installation costs of Larger meters are also available, suitable for systems where large controlled volumes of water are needed in a short time, eg CIP. Give direct readings of instantaneous flow. Ultrasonic meters Pipework. Strap-on ultrasonic meters may not be appropriate for older pipework. Useful where a non-invasive system is required, for hygiene reasons or to avoid pressure drop across a metering element. Weirs and flumes, to measure levels and hence flow. Pressure gauges Pipes, channels, weirs and flumes, to measure levels and hence flow. Invasive system.

14 Process water use This Section deals with the way you use water as part of your production system, and suggests simple practices and devices to improve water management and so reduce the amount of water needed. All this information and more is on our website at Simple measures such as not leaving taps or hoses running and fixing leaks can bring substantial savings in water supplies. There are also many simple and easy-to-install devices which will make it easier for you to save water. Making staff aware of how much water costs and how much is used in different processes is also key to controlling use. Remember that by minimising the water you use, your production processes will also create a lower volume of effluent. This will reduce your effluent discharge costs, saving you even more money. Process water

15 Envirowise Process water use 14 Water saving practices Opportunity Reason Action Are your staff aware that your water supply is metered? Are your staff aware of the need to take simple action such as turning off taps properly? Do you repair dripping taps immediately? Do you make regular checks for leaks in your water system, including underground/hidden sections? Staff are often unaware that commercial/ industrial water supplies are usually metered. Raising staff awareness can encourage more efficient water use. Taps and hoses which are left running when water is not needed, or not turned off properly, waste water. Hot water taps left dripping also waste energy. Dripping taps cost more money in wasted water than you might realise and may undermine the credibility of your savings campaign. How much water does a dripping tap waste? Visit the Process water use section of the water minimisation web site, and go to Water loss from an open tap. Regular checks for leaks will help to reduce the amount of water lost. Underground leaks can go undetected for many years. How much water do leaking pipes and valves waste? Visit the Process water use section of the water minimisation web site, and go to Water loss from leaking equipment. Use staff meetings as a way to raise awareness of water costs. Use promotional materials, eg posters and stickers, around your site. Post up weekly readings from water meters so staff can look at trends in usage and be aware of any problems. Use staff meetings as opportunities to discuss water-saving actions. Switch off process water feeds during breaks in processing. Use promotional materials, eg posters and stickers, around your site. Carry out regular checks on all outlets. When dripping taps are reported, act immediately and set an example to your staff. Carry out regular checks of accessible pipework and encourage staff to report any leaks they spot. Check for leakage in hidden pipework by monitoring your water meter. Look out for consumption during periods of non-use, which suggests leakage.

16 Opportunity Reason Action If you use sprays to wash or cool materials or product, are the nozzles regularly maintained? Are tamper-proof valves fitted on pipes that carry water to specific processes? Do you need to use water at a particular temperature? If you use mains water for cooling purposes, have you looked at any alternatives? Do you re-use any of your process water before it joins the effluent stream? Worn or heavily scaled spray nozzles are inefficient and can result in more water being used. Unauthorised valve operation can result in more water than necessary being used. Water running though long systems of pipework can lose or gain heat. This means the water is often run to drain to achieve the correct temperature. Using mains water once only, for cooling, is wasteful. Discharging wastewater to effluent streams can be wasteful; in some cases this water might be of sufficiently high quality to be re-used. In hard water areas, descale nozzles each month. In soft water areas, check regularly for worn nozzles and replace as necessary. Fit leather or cloth straps to prevent unauthorised operation. (These can be cut easily in emergencies.) Do not remove handwheels from isolation valves, as operators may try to use spanners to operate the valve, and so damage the spindle. Lag or trace-heat long runs of pipework to reduce heat loss or gain. Consider other sources of cooling water grey water, processquality water and borehole, river or canal water. These are costeffective but seek advice first. You could also re-use cooling water as feed water or make-up water in other equipment. Consider installing cooling water systems using recycling through a closed system fitted with an air blast cooler. Check the quality of the water. It may require treatment to reduce contamination. Think about where it could be re-used. Note Consider the strict hygiene standards in the food and drink industry. Make sure the costs of treating recycled water to achieve the right quality do not outweigh the water savings. Consider re-use in non-food applications or as a pre-rinse in countercurrent rinsing. Ensure re-used water will not taint or discolour food products. Visit the Process water use section of the water minimisation web site, and go to Countercurrent rinsing for more information. Envirowise Process water use 15

17 Envirowise Process water use 16 Water saving devices Opportunity Reason Action Do you have the right pressure or rate of flow through pipes and other equipment? Are hoses turned off after use or when unattended? Is your water supply metered in more than one place? Do you use water sprays to wash or cool raw materials or product? Do you use high pressure jets and sprays to wash raw materials? Do you use plant with a preset or adjustable flow of water? Some processes or pieces of equipment may not need a high pressure or rate of flow. You may be using more water than necessary. Hoses left turned on unnecessarily can waste large quantities of water. How much water do running hoses waste? Visit the Process water use section of the water minimisation web site, and go to Water loss from leaking equipment. Water meters will help you to establish how much water you use. Only then can you decide where you can make the most savings. Using the right type of spray nozzle is very important but is often not considered. Focusing the spray can significantly increase efficiency and reduce water use. Using hoses, tanks and baths of water for washing consumes a great deal of water. Flow rates are usually adjusted by setting a control valve. Control valves may also be used to isolate the water supply and are then not reset to the optimum flow position. Check manufacturers specifications for individual pieces of equipment to check whether the water pressure or flow rate is higher than specified. Fit pressure control valves or flow restrictors to pipes. Fit trigger-operated controls to hoses. Install water meters on supplies going into individual processes so you can see how much different processes or areas use. Talk to your equipment supplier about which types of nozzle are most suitable for your process. For example, directional nozzles that spray large drops in a cone pattern are best for chill rooms. Visit the Process water use section of the water minimisation web site, and go to Choosing the right spray nozzles for more information. Consider using high pressure jets and sprays. New designs also operate at lower pressures while maintaining cleaning and hygiene requirements. Consider fitting block valves instead of control valves; this will avoid the need to change preset positions.

18 Opportunity Reason Action Do you have any way of limiting water wastage if pipework fails? Do you use dry conveyors or chutes to transfer materials in your process? Do you use air or microwave thawing techniques? If pipework fails, you will probably be charged for all the water that has been wasted as well as suffering damage to your site and operations. Flumes can use a lot of water and this is often discarded. Many businesses use makeshift water thawing techniques which are uncontrolled and use large quantities of water. This is most appropriate for commercial areas and dry operations, where a flood could cause major disruption. Consider installing leakage prevention systems, which could save most of the costs of a flood. Consider dry handling methods if appropriate and practical. Flumes are generally kinder to product than dry conveyors or chutes, so in these situations, consider re-using flume water if hygiene standards allow. Talk to suppliers about other thawing methods, such as or warm air or microwave thawing. If you use water thawing techniques, insert thermocouples into the centre of frozen blocks to automatically turn off the water supply when the material has thawed. Envirowise Process water use 17

19 Envirowise Process water use 18

20 Process control This Section describes how you can use process control to optimise water use. Effective process control enables water to be used more efficiently. It reduces the amount needed in your processes and also the volume that joins effluent streams. This will bring substantial savings on your water supply and effluent bills. All this information and more is on our website at Process control methods range from individual, simple-to-install devices to fully automatic process control systems managing all the processes on a site. You do not need to automate everything to realise savings; a few simple automatic devices linked to your key water-using processes can make a great deal of difference. Most process control systems are made up of three distinct elements: sensors, transmitters and control devices. These can be used to control temperature, pressure, level and flow, and to carry out more detailed analytical measurements of content, such as ph. The tables provide guidance on selecting the most appropriate control options, and summarise the types of sensor and control device available and some key criteria for their selection. Cost indicators are also provided. Capital and installation costs are a maximum and cheaper prices may be found. Visit the Process control section of the water minimisation web site, and go to Control devices and Installation requirements for measurement sensors for more detailed information. In all cases, remember to check hygiene requirements before fitting intrusive devices into process equipment. Visit the Process control section of the water minimisation web site, and go to Hygiene for more information. Process control

21 Envirowise Process control 20 Select an appropriate control option Check point Comment Example Do you need measurement data? If so, you should consider: Location are the readings needed locally on the plant or in a control room? Measurement point is it in a pipe, open tank or closed vessel? Accuracy and repeatability the tighter the control required, the more important these become. Data on water flows or tank level would be used only for controlling water overflow from the tank. Data are not needed for process monitoring. Do you only need control? Do you need measurement and control? What will it cost? Are there any other operational issues? Flow and level controls are often the simplest and cheapest control options to install and operate. If so, you should consider: response time; accuracy. Consider installation and maintenance costs as well as the capital cost. Ensure the options are consistent with the overall control philosophy and compatible with control system standards. A control-only device such as a float valve could prevent water overflow. A control loop to prevent water overflow from a tank will be based on measurement of tank level or water flow rate. It does not require a rapid response time or high levels of accuracy or repeatability. A simple float valve will be the cheapest to purchase, install and maintain, and is also the most appropriate option. Manual control valves may not be appropriate for processes controlled mainly from a remote control room. Many processes are operated to standards that specify the instruments and equipment to be used.

22 Use sensors to monitor your site processes Device Operating parameters Accuracy Repeatability Costs based on 2002 prices Maintenance Applications Temperature Resistance thermometers 240 to +650 C ± 0.05% High capital installation Low cost. Maintain annually. Widely used, especially for accurate measurement over a limited range. Devices available for hygienic and nonhygienic applications. Needs electricity. Thermocouples 270 to C ± 0.05% Moderate capital installation Low cost. Maintain annually. Widely used. Devices available for hygienic and nonhygienic applications. Needs electricity. Filled-system thermometers 270 to +810 C ± 0.2% Moderate < 100 capital < 500 installation Low cost. Maintain annually. Limited use only for local measurement or indication. Modern transmitters offer more advantages. Devices available for non-hygienic applications only. Optical thermometers 25 to1 100 C ± 0.2% Moderate > 500 capital < 500 installation Low cost. Maintain annually. Limited use for surface temperature measurement only. Do not provide a signal for process control purposes. Needs electricity. Pressure Diaphragm pressure sensors 20 to +85 C Vacuum to 40 bar ± 0.1% Moderate capital < 500 installation Low cost. Maintain quarterly. Widely used. Devices available for hygienic and nonhygienic applications. Needs electricity. Differential pressure sensors 40 to +85 C 0 to 6 bar ± 0.1% High > 500 capital installation Low cost. Maintain quarterly. Used for pressure control where process and device are separated. If necessary, maintenance can be yearly. Needs electricity. Level Float valves 0 to100 C Height range (m) between device and max liquid level: n/a n/a n/a capital < 500 installation Low cost. Maintain monthly. Control at a single point. No measurement. Envirowise Process control 21

23 Envirowise Process control 22 Device Operating parameters Accuracy Repeatability Costs based on 2002 prices Maintenance Applications Mechanical indicators and float switches 0 to 100 C height range <10 m Low Low capital < 500 installation Low cost. Maintain monthly. Control at a single point. Local measurement only. Capacitance level switches 0 to 100 C <15 m ± 0.1% (High) High 100 > 500 capital < installation Low cost. Maintain annually. Widely used. Devices available for hygienic and nonhygienic applications. Needs electricity. Vibrating level switches <100 C <20 m ± 0.1% High 100 > 500 capital installation Low cost. Maintain annually. Widely used. Needs electricity. Conductivity switches 0 to 100 C <20 m ± 0.1% High 100 > 500 capital 100 > 500 installation Moderate cost. Maintain annually. Widely used. Needs electricity. Hydrostatic devices 0 to 100 C Range limited by pressure of head above measurement point ± 0.1% High > 500 capital 100 > 500 installation Moderate cost. Maintain monthly. Control and measurement at a single point. Devices available for hygienic and non-hygienic applications. Needs electrical or pneumatic power source. Ultrasonic sensors 0 to 100 C <45 m ± 0.1% High > 500 capital installation Low cost. Maintain monthly. Control and measurement at a single point. Devices available for hygienic and non-hygienic applications. Needs electricity. Microwave devices 0 to 100 C <20 m ± 0.1% High > 500 capital > installation Low cost. Maintain monthly. Control and measurement at a single point. Devices available for hygienic and non-hygienic applications. Needs electricity. Flow Variable area (rotameter) 10 to 100 C Turndown 10:1 ± 2% Medium < 100 capital < 500 installation Low cost. Maintain annually. Local measurement only. Mainly low-flow and nonhygienic applications.

24 Device Operating parameters Accuracy Repeatability Costs based on 2002 prices Maintenance Applications Positive displacement meters 10 to 100 C Turndown 10:1 ±0.75% High > 500 capital installation Moderate cost. Maintain annually. Hygienic and non-hygienic applications. Not suitable for high viscosity materials or CIP. Turbine meters 0 to 300 C Turndown 10:1 ±0.75% High 100 > 500 capital installation Moderate cost. Maintain annually. Widely used for water. A wide range of sizes is available. Electromagnetic meters 0 to180 C Turndown 100:1 ±0.75% High > 500 capital > installation Low cost. Maintain annually. Non-intrusive sensor, thus minimising hygiene issues. Needs electricity. Ultrasonic transit time meters 0 to 100 C Turndown 20:1 ± 2% Moderate > 500 capital > installation Moderate cost. Maintain quarterly. Non-intrusive sensor, thus minimising hygiene issues. Needs electricity. Vortex shedding meters 0 to 400 C Turndown n/a ±0.75% High > 500 capital > installation Low cost. Maintain annually. Mainly used for steam and gas, but can be used for low viscosity fluids. Needs electricity. Differential pressure meters 0 to 500 C Turndown 4:1 ± 2% Moderate > 500 capital installation Moderate cost. Maintain monthly. Widely used. Devices available for hygienic and nonhygienic applications. Needs electricity. Analytical ph probes 0 to 130 C ph 1-14 Moderate/High Low/High capital installation Low/moderate cost. Maintain monthly/ annually. Simple systems that are low/moderate cost to purchase, install and maintain. Needs electricity. Conductivity electrode cells 160 C 0.04 ms/cm 200mS/m Moderate/High Low/High > 500 capital installation Moderate cost. Maintain monthly/ annually. Widely used for services control, eg monitoring boiler water, process water and steam condensate. Needs electricity. Conductivity inductive sensor 5 to +100 C mS/m Moderate/High Low/High > 500 capital installation Low/moderate cost. Maintain monthly/ annually. Ideal where there is contact with the product, thus minimising hygiene concerns. Needs electricity. Envirowise Process control 23

25 Envirowise Process control 24 Device Operating parameters Accuracy Repeatability Costs based on 2002 prices Maintenance Applications Turbidity scattered light devices 0 to 50 C mg/litre Moderate/High Low/High > 500 capital installation Moderate cost. Maintain monthly/ annually. A sampling device may be needed. Needs electricity. Turbidity suspended solids meters 0 to 50 C 0 300g/litre Moderate/High Low/High > 500 capital installation Moderate cost. Maintain monthly/ annually. Particularly useful for effluent monitoring and treatment. Needs electricity.

26 Use control devices to optimise water use Device category Application Operating parameters Costs Maintenance Device type Guidance Manual or fixed control Variety of devices available to set flow at specified rate, eg a restricting orifice, or to control flows manually, eg needle valves. Operating range (turndown) depends on the size of device. Operating temperature is a maximum of C. < capital < 500 installation Low cost. Maintain weekly/quarterly; check settings of manual valves regularly. Globe and angle valves Needle control valves Suitable for low viscosity fluids containing no solids. Angle valves have a lower pressure drop across the valve than globe valves. Allow accurate manual control. Suitable for low viscosity fluids with minimal solids. Butterfly valves These valves have lower pressure drop and are suitable for higher viscosity fluids or those containing solids. Less accurate control than needle, globe or angle valves. Weir diaphragm valves Simple and low-cost, offering moderate control. Suitable for higher viscosity fluids or those containing solids. Restricting orifice Provide a constant flow at a predetermined rate. Orifice plates are susceptible to erosion and build-up of solids. Flow regulators Adjustment possible within a limited range; designed with the intention that adjustment will be infrequent. Solenoidactuated Used for two-point control only, eg on/off. Operating range (turndown) depends on the size of device. Operating temperature depends on the valve design. Needs electricity. < capital < 500 installation Low cost. Maintain quarterly. Valves Used to open or close a valve on receipt of a control signal. Simple and low-cost. Frequently used to control water supply. Envirowise Process control 25

27 Envirowise Process control 26 Device category Application Operating parameters Costs Maintenance Device type Guidance Automatic control More expensive option, but essential when flow rates have to be controlled accurately and need to respond quickly to changes in the process condition. Operating range (turndown) depends on the size of device. Operating temperature depends on the valve design. Needs electrical or pneumatic power supply. 100 > 500 capital 500 > installation Low/moderate cost. Maintain quarterly. Valves Accurate and variable control of flow rate, controlled by an actuator. Various types of valve can be used, including globe, butterfly, ball and three-way valves. The flow rate is adjusted automatically by the control loop, without intervention from an operator.

28 Product recovery techniques This Section discusses the techniques for recovering product which also save water and reduce effluent volume and strength. Separating out the different solids and liquids that enter the effluent stream has many benefits. All this information and more is on our website at First, it can provide the opportunity to recover water and re-use it. This will not only reduce the amount of water you need to pay for, but will also reduce the volume of effluent you will have to pay to discharge. Secondly, if you can separate raw materials or product from the water and recover these, you will be reducing the concentration of your effluent. This will lower your trade effluent bills. You may also have the benefit of recovering saleable product, which would otherwise be flushed down the drain. This Section focuses on two main product recovery techniques, pigging and membrane separation. These techniques enable either a reduction in the use of water or the recovery of water used in the process. Product recovery

29 Envirowise Product recovery techniques 28 Consider using a pigging system to reduce water usage Pigging. Use this table to help you decide whether investing in pigging may be worthwhile. A pig is a plug or ball that fits inside the pipe and is pushed through by either the product itself or by some other propellant. The pig empties the pipe and removes deposits adhering to the walls. Opportunity Is your product suitable for pigging? Do you currently use water to clean out your process pipework? Are you losing valuable product when you flush pipework with water? Do you have a long production downtime while pipes are cleaned? Is your pipework suitable for pigging or will additional investment be needed? Reason Any product that will flow can be pigged, eg sauces, jam, milk and juices. Pigging is worth considering if your site has waste streams containing potentially valuable products which would otherwise be wasted and would increase effluent strength. Flushing out pipework uses considerable quantities of water. A pigging system would reduce water usage. Using a pigging system instead of water means you can recover product left in the pipework as well as saving water. This will also reduce your effluent bills. Visit the Product recovery techniques section of the water minimisation web site, and go to Pigging saves water and recovers product to see an industry example. Pigging systems can clear pipework more quickly than cleaning with water. You need to look at the design of the process installation you want to clean. All valves must be full bore to allow the pig to pass through. This means that any butterfly or diaphragm valves would need to be changed. Pipework needs to be in relatively straight runs as the pigs would become trapped at corners.

30 Consider using membrane separation to recover water Membrane separation. A membrane is a thin physical barrier through which materials can either pass (the permeate) or be rejected and retained (the retentate). The structure and character of the membrane determine the nature of the separation. Membranes have many uses in the food and drink industry: apart from recovering water, they can be used to concentrate or purify product and recover raw materials and product from waste streams. Visit the Product recovery techniques section of the water minimisation web site, and go to Membrane separation technology for more detailed information. Opportunity Are you processing the sort of foods where membrane separation could be useful for reducing water costs and recovering product? Do your processes or products currently use or contain water which is then discharged as effluent? What types of membrane are there? Which type of membrane is suitable? Reason Waste streams which are high in protein and sugars will increase effluent strength, for example, if you process dairy products, potatoes or egg products, eg sauces and mayonnaise. Potentially high-value product or by-product is being washed down the drain with cleaning water. Using a membrane to separate the water from the other substances can allow you to re-use the water elsewhere on your site, for example as boiler feedwater. At the same time you could also recover the other, concentrated, materials and reduce the concentration of your trade effluent. Visit the Product recovery techniques section of the water minimisation web site, and go to Membranes bring savings at creamery to see an industry example. Membranes are categorised according to their pore size: microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Microfiltration uses the largest pore size, reverse osmosis the smallest. Commercial membranes are available in four main configurations: hollow-fibre, spiral-wound, tubular, and plate-and-frame modules. The membrane type you should select will depend on which substances you are separating. Microfiltration is used to remove particulate matter from liquid streams, typically the concentration of solids and oils from liquids and slurries. Tubular modules have superior capabilities when dealing with solids. Fish and abattoir wastes are typical applications. Ultrafiltration separates solutes from solids, colloids, emulsions and macromolecules. The filtration of fats and oils is a common application. Nanofiltration and reverse osmosis separate water from water solute mixtures. Reverse osmosis will provide absolutely pure water with no dissolved salts. Spiral-wound and tubular modules are most commonly used. Note It is essential that you discuss your needs with a membrane supplier before making a selection. Although membrane plant is available off the shelf, the wide range of processing activities means that you should consider any potential membrane application as unique until confirmed otherwise. Envirowise Product recovery techniques 29

31 Envirowise Product recovery techniques 30 Opportunity Are there any disadvantages to membrane separation? Reason Selection of compatible membrane is essential. Generally low selectivity. Membrane fouling is a common problem. Membrane life is finite and sometimes short. Capital investment may appear high. Payback period may be long in some situations. Conventional membrane technology may not be suitable for use in very high temperatures, and aggressive or fouling conditions.

32 Cleaning This Section looks at optimising cleaning activities in order to minimise water use. Cleaning can account for as much as 70% of a site s water use. Changing cleaning routines to optimise water use will not only cut your water supply bills but can have the added benefits of reducing the volume and concentration of effluent. Remember, too, that excessive use of water for cleaning brings many additional costs, such as labour, downtime, lost materials, cleaning chemicals and energy for heating and pumping. Visit the Cleaning section of the water minimisation web site, and go to Comparing savings from different cleaning methods for extra information. All this information and more is on our website at Cleaning is vital to ensure food safety, but overuse of water for cleaning tasks is common. It is also the case where there are concerns over hygiene that staff would rather be safe than sorry. The following tables illustrate opportunities for using cleaning techniques and technologies which will reduce water usage without compromising hygiene. Cleaning

33 Envirowise Cleaning 32 Water saving practices for cleaning Opportunity Reason Action Are your staff informed about efficient water use and trained to use the cleaning equipment? Raising staff awareness about how much water is needed and how to use equipment properly will help to save water. Use staff meetings to talk about good housekeeping practices and make them aware of water costs. Motivation is important. Set up training programmes to teach staff to operate cleaning equipment properly. Is your cleaning equipment set up to operate with the right flow rate or water pressure, or the right number or duration of wash cycles? Do you use automatic washers to clean containers etc? Do you use the most appropriate chemical cleaners for the task? Is your cleaning equipment inspected and maintained regularly? Equipment can often be set up incorrectly and be using more water than is needed, because flow rate or pressure has been increased or wash cycles have been extended. If washers are run when they are not full this wastes water, as the same amount is used. If contents are not stacked properly they may not be cleaned efficiently and will have to be washed again, which is also wasteful. Some chemical cleaners may not be ideal for all cleaning jobs. Chemicals which are not efficient can necessitate repeated cleanings and so more water is used. Some chemical residues are harder to remove and might require excessive rinsing with water. Faults that are not dealt with promptly can mean that a piece of equipment is operating inefficiently. This can lead to more frequent cleaning being necessary and more water being used. Check the settings of your cleaning equipment against the manufacturer s specifications. Adjust accordingly. Run washers only when they are full and ensure that they are stacked properly. Note Automatic container washers can give water savings of up to 95% compared with pressure-cleaning your containers. Visit the Cleaning section of the water minimisation web site, and go to Container washers for more detailed information. Ensure that the cleaning chemical used is the one best suited for the job. Consider using foam and gel cleaners instead; they require less rinsing. Set up a regular inspection programme for cleaning equipment, and make sure faults are dealt with as quickly as possible. Encourage staff to report faults immediately.

34 Opportunity Reason Action Do you use dry cleanup methods to remove product waste from vessels, equipment and floors? Do you carry out a reduced clean at some product changeovers? Do your automated cleaning systems have short cycle durations available? Do you clean surfaces, equipment and vessels immediately after use? Do you re-use wash water? Using water to flush away waste increases water consumption considerably. It also means the volume and concentration of trade effluent will be higher. In some situations, it may be possible to carry out a reduced clean rather than a full clean by processing similar products sequentially. A long washing cycle may not be necessary for all of the items that need to be cleaned. Some waste products can quickly become dry and encrusted and harder to clean off. Wash water is often flushed down the drain because it has been used. It may be reusable for certain applications on your site. Use dry clean-up methods to remove waste product from surfaces before a final clean with water. Scrapers, squeegees, brushes and brooms are ideal. The Section Product recovery techniques in this folder may also be helpful. Rearrange your product scheduling so that similar products are processed one after the other and that you start with lightcoloured products and progress to darker ones. You may then be able to reduce the number or duration of cleans between products. You may want to schedule the more highly-flavoured products last. If possible, use shorter cleaning cycles for small items or items that are easy to clean. This will save water while still maintaining hygiene standards. Try to ensure cleaning is carried out as soon as production or part of a production process has finished. Think about how and where the water might be re-used. Consider hygiene requirements and whether the recycled water would need treatment. The table about membrane technologies in Product recovery techniques in this folder may also be helpful. Consider countercurrent rinsing. The item is rinsed first in grey (used) water and then in progressively cleaner water for each following rinse. At the same time, the rinse water moves from the last rinse (clean water) towards the first rinse (grey water). Typical water savings are around 40%. Visit the Cleaning section of the water minimisation web site, and go to Countercurrent rinsing for more information Envirowise Cleaning 33

35 Envirowise Cleaning 34 Water saving devices and equipment for cleaning Opportunity Reason Action Is cleaning equipment switched off immediately after cleaning is complete? Hoses and automatic washers left running when not in use waste a great deal of water. Fit trigger-operated controls to hoses. Consider automatic switch-off mechanisms which will cut off the water supply when the cleaning task is finished. Are surfaces, vessels and equipment easy to clean? Do you currently use any spray or jet washing systems? Do you use pressure washers for cleaning surfaces or equipment? Surfaces, vessels and equipment that includes sharp angles, dead spaces etc, will be unhygienic and harder to clean, requiring longer cleaning cycles and more water. These are generally efficient but the technology has advanced in recent years. Poor maintenance practices can also damage nozzles and reduce efficiency. Hoses and other low pressure/ high volume methods use large quantities of water and are a less efficient way of cleaning equipment. When replacing pieces of equipment, ensure that: all equipment is made of material which will be resistant to corrosion, tainting and abrasion (eg stainless steel); surface finishes and joints are smooth and continuous; sharp angles and corners are avoided; all pipes and vessels are self-draining; screw threads, nuts and bolts etc do not come into contact with the product. Visit the Cleaning section of the water minimisation web site, and go to Hygiene for more detailed information. Talk to manufacturers about the latest designs which are suitable for your cleaning processes. These are less susceptible to blockage and have improved water efficiency with no reduction in cleaning effect. Visit the Cleaning section of the water minimisation web site, and go to Improved cask washing plant saves water to see an industry example of how improved plant saves water. Ensure nozzles are not descaled using a drill, which increases the nozzle size and hence the flow rate. Consider using pressure washers instead. Pressure washers use up to 60% less water than hoses. Note Pressure washers installed on a factory ring main are more costly but have a short payback period. Consider automatic washers for cleaning containers as these use even less water. Visit the Cleaning section of the water minimisation web site, and go to Pressure washers for more detailed information.

36 Opportunity Reason Action Do you use automated CIP (cleaning-inplace) systems? Are floors cleaned with industrial machine cleaners? Are food processing benches welldesigned? Manual or soak-cleaning methods can use excessive amounts of water and may not always clean efficiently. Cleaning floors manually by washing down with water can use a great deal of water and chemicals. Material processed by hand on workbenches can often fall or be dropped on the floor. Consider installing automated CIP systems. These are highly efficient as process equipment, tanks and vessels are cleaned in place. As there is no human contact, stronger detergents ensure more efficient cleaning and water use is optimised. Visit the Cleaning section of the water minimisation web site, and go to Cleaning-in-place (CIP) systems for more detailed information. Consider using a scrubber dryer or industrial vacuum cleaner. These can perform wet or dry cleaning and can remove gross soiling prior to washing with water, reducing effluent load and the amount of water needed for cleaning. Scrubber dryers wet-scrub floors efficiently using a relatively small amount of water. These can be expensive but the payback period will be short. Note There can be hygiene risks with some machine cleaners. Think about redesigning processing benches to include catch trays or lips to help reduce the amount of material dropped on the floor. This will reduce the need for floor cleaning and the likelihood of solids being washed to drain. This can be expensive but the payback period will be short. Envirowise Cleaning 35

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38 Ancillary water use This Section looks at practices and devices to reduce water consumption in areas of your site not directly related to production. These areas include staff facilities such as kitchens, laundries, washbasins, showers and toilets. All this information and more is on our website at Applying some basic, and often low-cost, water saving measures can result in up to a 40% reduction in water use in these ancillary areas. Ancillary water