With such high volumes of water involved in food and beverage production, and the cost of raw water and wastewater disposal on the rise, manufacturers are looking to more advanced and innovative solutions to meet water treatment obligations. Here, Paul Winnett, General Manager – Speciality Industries at Xylem, explains how water re-use in manufacturing can ensure reliable and cost-effective water management.
According to a report by The Institution of Mechanical Engineers, 70 per cent of water used annually by humans is consumed by the global agriculture sector. With statistics like this, it is easy to see why food and beverage manufacturers are deploying water re-use methods which ultimately help to alleviate business risk, enhance sustainability practices and safeguard water quality standards by decreasing the plant’s dependency on external water sources.
One way of reducing Mogden Charges is to treat or re-use water before discharge. Water re-use is the practice of re-using suitably treated wastewater from one process in another industrial process and can significantly reduce the demand on potable sources of freshwater and the volume of water discharged to the sewer. The food processing industry is ideally suited to this process.
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As a result, re-use is a way of meeting discharge standards, reducing cost and as an aid to helping food processing businesses who have maximised their daily demand for water, particularly if the business is metered.
Crucially, water re-use technology is included in the government’s Water Technology List which promotes the use of technology for water re-use and more importantly, rewards businesses, in the form of the Enhanced Capital Allowance Scheme (ECA), who invest in them via tax relief.
Water re-use in manufacturing
There are two ways to reuse water in manufacturing. The first, direct water re-use, feeds water back into the production process, but this isn’t a popular choice within the food and beverage industry as the re-used water supply will come in direct contact with the end product.
However, the second, indirect water reuse, can provide a cost-effective supply for machine wash-down, cleaning floors, boiler feed or similar duties. The question is how do food and beverage manufacturers implement these measures which are not only beneficial to the environment but also the bottom line?
The truth is that the cost of water as a raw material is not high. Manufacturers can develop proposals to recover process water, but this could be costly and the payback may be several years. For example, from an environmental point of view, a scheme to recover process water is a positive step, but the additional equipment and space required to house the re-use water may not be commercially viable to implement.
To avoid the hidden costs of water usage, you need to look beyond the cost of the water itself and evaluate the processes used to treat it. But with the market saturated with available solutions, identifying the right treatment option can be difficult.
Identifying the right treatment option
There are a wide variety of technologies available for wastewater treatment in re-use applications. From conventional treatment processes, which can remove solids, and adjust pH and chlorine levels, through to advanced processes which filter and oxidise water resulting in a higher quality product.
A conventional treatment process removes solid waste found in water. This provides minimal disinfection and include the use of screens, dissolved air flotation and primary clarifiers, filters, chlorination and pH adjustment, reducing solids and Biochemical Oxygen Demand (BOD).
When a conventional treatment process isn’t adequate for meeting required treatment standards, advanced treatment technologies can be implemented. These technologies go further to remove contaminants than conventional treatment processes and are implemented for specific needs. These include the removal of trace contaminants and pathogens via oxidation and disinfection through to the removal of dissolved organics and contaminants via an adsorption process.
In addition to the biological and disinfection techniques, there are other advanced treatment technologies such as membrane filtration and reverse osmosis that can be used either separately or in conjunction with one another to fulfill wastewater discharge requirements.
What is important to remember is that treating water is only the first step to ensuring wastewater is recycled and reused efficiently and effectively within a plant. It is important for organisations to also consider the transportation and storage of water re-use.
Pumping systems
The treatment and transportation of water or wastewater within a system will require the biggest source of energy. Therefore it is vitally important that the system is not only correctly sized, but the right equipment selected in the first instance, to ensure specific re-use requirements are met as well as maximising energy savings over the life of the equipment.
Pumps serve two purposes in a re-use system: transporting and pressure boosting. Water needs to be moved from one location to another for treatment, storage purposes, or for use.
Pressure boosting is required for some treatment technologies, including reverse osmosis, where specific pressures are required to move water through a membrane. Many reuse applications, such as equipment washing, also require boosting capabilities.
Considerations for water reuse in manuafacturing
To implement an effective water re-use system, it is important to address the following three key areas:
- Define objectives: When deciding what type of water reuse system is needed in a facility, a plant must define its objectives both from sustainability and cost perspectives and in-line with water treatment obligations.
- Select applications: Plant owners and/or operators should define the applications for which the water will be used. It is advised to start with high-volume re-use applications that have lower water quality requirements, therefore requiring less treatment. By following this approach, the facility will achieve the greatest return on investment, as higher levels of treatment drive costs up.
- Determine treatment levels: Finally, determine the treatment levels required for the selected applications by measuring current wastewater quality to establish a baseline, and then compare that to the quality level required for the selected applications. This gap in water quality will determine the treatment intensity.
