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Wastewater treatment: what’s the score?

09 January 2015

With so many wastewater treatment technologies on the market, what do food processors need to know before they select which one works best for them?

For companies working the food and drink industry, wastewater treatment is becoming an important strategy for several reasons. It’s no secret that the global agricultural sector consumes around 70% of water used each year by humans, so it’s hardly surprising that food and drink manufacturers and processors are utilising water re-use methods to help alleviate business risk, enhance sustainability practices and safeguard water quality standards to decrease the site’s dependency on external water source.

There are also new guidelines which came into force on 1 July 2014 for companies who breach environmental legislation that can enforce fines of up to £3 million, and now state that the size of the fine is dependent not only on the nature of the offence, but also the size of the offending organisation. For medium to large food and drink producers, this could mean a significant increase in the size of fines.

There is particular attention to breaches of environmental legislation related to illegal discharges to controlled water and/or illegal disposal of waste. Fines can vary from £100 - £700 for an unintentional minor incident by a small company to £450,000 - £3 million for a deliberate act causing major pollution by a large company. On average, a typical pollution incident caused by negligence by a large company could result in a fine of £22,000 - £750,000.

With such high volumes of water used in the industry, the cost of raw water and wastewater disposal on the rise and with the new guidelines for breaching environmental legislation, companies are looking for advanced and innovative solutions to meet their water treatment obligations.

“Effluent treatment is becoming part of the on-site energy recovery sector,” says Richard Gueterbock from Clearfleau. “As energy prices increase, companies can generate value from wash waters and discarded materials. With both Scotland and Wales banning disposal of food waste to landfill and discharge to sewer, there is pressure on food processors to raise their environmental standards and develop alternative disposal routes.”

Water reuse

“One way of reducing Mogden Charges is to treat or reuse water before discharge,” says Paul Winnett, General Manager – Speciality Industries at Xylem. “Water reuse is the practice of reusing the 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. As a result, reuse 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.”

An added incentive is that water reuse is included in the Government’s Water Technology List, which promotes and rewards businesses who invest in water reuse technologies via tax relief in the form of the Enhanced Capital Allowance Scheme (ECA).

Of the two ways to reuse water in manufacturing, only one is a popular choice for the food industry. Direct water reuse, which feeds water back into the production process, would involve the reused water to come into direct contact with the end product. The more popular choice is to reuse water as a cost-effective supply for machine wash-down, cleaning floors, boiler feed or similar duties.

“The truth is that the cost of water as a raw material is not high,” explains Winnett. “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 reuse 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.”

Water disposal

Manufacturers should also be aware of factors that affect the disposal of their effluent. “Make sure that sudden increases in production, which can be a factor with seasonal businesses, are strategically planned for, and that the effluent treatment process has enough headroom to cope,” advises Clwyd Jones of Siltbuster Process Solutions. “And be aware that changing either the product produced or the production method can result in a completely different effluent, and unless it’s planned for, the changed waste stream could very negatively affect the treatment process.”

Jones also suggests installing key standby or additional treatment equipment at the effluent water treatment plant. “Consider installing a divert tank or calamity tank to temporarily store discharges related to incidents, or strong/difficult waste streams from where they can be bled back into the water treatment plant at a manageable rate or tankered offsite,” says Jones. “And have a tried and tested process in place for quickly identifying and isolating the cause when things go wrong. Once you’ve eliminated the obvious, check for changes to effluent volume / characteristics or records of any incidents, plus other changes such as new shift patterns or a transient workforce, unreported spillages, changed production methods / cleaning agents as these factors can all affect the waste discharged.”

Other suggestions include putting a contingency plan in place that sets out what to do if the effluent plant fails and where to mobilise emergency treatment from, whether that’s temporary storage tanks, tankering offsite to the nearest suitable waste acceptance site or to hire replacement effluent treatment technology; regularly review the performance of the effluent treatment plant and update the contingency plan to reflect production changes; and to raise awareness of effluent treatment within the organisation by educating production personnel and managers on how the effluent plant works and its limitations, thereby reducing the risk of production activities causing an incident.

The right treatment?

From conventional treatment water reuse processes that remove solids and adjust pH and chlorine levels to advanced processes that filter and oxidise water which results in a higher quality product, which is the right choice?

“A conventional treatment process removes solid waste found in water,” explains Winnett. “This provides minimal disinfection and includes 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 isn’t adequate, advanced technologies can be implemented which go further to remove contaminants 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.

There are also other advanced treatment technologies such as membrane filtration and reverse osmosis that can be used either separately or in conjunction with one another to fulfil wastewater discharge requirements.

UV disinfection

Ultraviolet (UV) technology kills all known microorganisms, including bacteria, viruses, yeasts and moulds and their spores. “Unlike chemical treatment, UV doesn’t introduce toxins or residues as disinfection by-products,” says Tim McDougie, Sales and Marketing Director at Hanovia. “It can be used for primary disinfection or as a backup for other wastewater treatment methods such as filtration. UV can be used to disinfect the water used to wash process equipment, work surfaces or produce can dramatically decrease contamination, increasing shelf-life. Fully automated UV disinfection systems can be integrated with CIP rinse cycles to ensure final rinse water does not reintroduce microbiological contaminants.”

And while reusing wastewater can mean a dramatic reduction in discharges to watercourses, any effluent that doesn’t have to be discharged can be disinfected with UV to meet with local environmental regulations.

“Food and drink processors are increasingly getting caught between conflicting sets of regulations,” says McDougie. “While food hygiene regulations in many countries require increased use of water to rinse produce and process equipment, environmental regulations are limiting the amount of fresh water that a plant can consume. With only so much fresh water coming in, sites are forced to reduce capacity in order to meet these conflicting requirements. By using disinfected wastewater in non-contact applications like chillers and cooling towers, more fresh water can be devoted to washing and processing.”

UV systems can in most cases be integrated straight into process systems with minimal disruption to plant operations and maintenance requirements are minimal too.

Anaerobic digestion

While larger centralised anaerobic digestion (AD) facilities are an option for dealing with effluent waste, localised plants can offer a better solution for on-site energy recovery, enabling food processing and farm residues to be converted into renewable energy when they are produced, according to Gueterbock. “On-site digestion of wastewaters and residues from food and drink processing sites is a largely untapped market,” says Gueterbock. “Digestion at the point of production avoids off-site transport of residues and reduces treatment and disposal costs. Energy generated from biogas and used onsite qualifies for renewable energy incentives and combined with savings on purchase of fossil fuels, these will contribute to an attractive return on investment.”

AD can be installed as part of existing onsite wastewater treatment plants to replace any outdated, energy intensive aerobic systems and provide for grey water reuse. Efficient onsite digestion can remove up to 98% of biodegradable load from food and drink production residues. “In 2014, Scotland introduced a ban on food residues being sent to landfill,” Gueterbock points out. “By 2016, all biodegradable wastes will be excluded. The ban includes sewer discharge of liquid production residues. It’s time that policy makers in England introduced similar measures to minimise the use of landfill.

“Multiple AD plants on food factory sites will help the UK to meet its renewable energy and emissions reduction targets,” continues Gueterbock. “Converting liquid production residues into energy that can replace some of the fossil fuels used in the factory, while providing increased treatment efficiency, should be actively supported by a Government who needs to rediscover its green credentials. The Department of Environment, Food and Rural Affairs (DEFRA) could do more to support AD plants being installed where biodegradable residues are generated on industrial sites.”

Considerations for water reuse

There are three key areas to address before implementing any water reuse system, according to Winnett. “Firstly, when deciding what type of water reuse is needed in a facility, a plant must define its objectives both from sustainability and cost perspectives and in line with water obligations. Secondly, operators should define the applications for which the water will be used. It’s advised to start with high volume reuse applications that have lower water quality requirements, therefore requiring less treatment, so the facility will achieve the greatest return on investment as higher levels of treatment drive costs up. And 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, and this gap in water quality will determine the treatment intensity.”

“With technologies capable of delivering real bottom line benefits, plus new sentencing guidelines in place to focus minds, there has never been a better moment to review wastewater treatment practices,” says Jones.

As pressure increases on food processors to conserve water and reduce usage, water reuse and effluent treatment enables food and drink manufacturers to not only meet the strictest treatment obligations but can also lead to significant cost reductions and a meaningful opportunity for a more sustainable future.

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