Potato Waste Becomes Clean Water, Energy

Engineered wastewater-effluent-treatment systems are generating 45,000 liters of potable water per hour and 3.2 MW of green energy.

Food and beverage processing involves a significant amount of wastewater, most commonly treated in a typical anaerobic–aerobic wastewater-treatment plant. The effluent produced from this conventional type of treatment is an ideal source for further refining into perfectly hygienic, potable drinking water, and clean energy—something that can help plants save on water intake and energy costs.

While biological effluent use is a popular way to improve plant efficiency, it’s not as easy as it seems. In the food and beverage industry, three conditions must be met:

• All production must allow the reuse of biological effluent.
• The available effluent must be of an acceptable quality, allowing successful tertiary treatment.
• The generated concentrate should still be disposable.

Waterleau (Leuven, Belgium, and Victor, NY) is a global provider of environmental technology and a pioneer in water and wastewater treatment that offers a variety of solutions for processing wastewater in the food and beverage sector. The company works with individual plants to design and build solutions based on their respective projects and treatment conditions. An example of this is Farm Frites, headquartered in Molendjik, The Netherlands.

In the Farm Frites effluent-treatment plant, backwash and concentrates from membrane treatment are recycled in the wastewater-treatment process, which allows recovery of 45,000 liters of safe drinking water each hour.

Reducing water footprint

With a global capacity of 1.3-million tons of processed potatoes annually and 1,500 employees, Farm Frites (farmfrites.com) is one of the largest operations of its kind in the world. Over the years, though, this successful company has faced groundwater scarcity, limited groundwater-permit availability, increased costs of sourcing tap water, and stringent wastewater-discharge regulations.

To deal with these challenges, Farm Frites partnered with its drinking-water supplier, De Watergroep (Brussels). Together, the organizations developed a sustainable, tailor-made solution that met the potato-processor’s water demand and complied with the governing water agency’s strict regulatory framework.

De Watergroep, in turn, partnered with Waterleau for the design and construction of the wastewater-effluent-treatment solution. Waterleau’s Boomerang water-reuse technology consists of a successive ultrafiltration (UF) and reverse osmosis (RO) treatment process that converts wastewater into potable water that can then be reused in
the plant.

Ultrafiltration membranes provide a physical barrier to remove bacteria, suspended solids, and harmful pathogens. This technology has been proven in many water reuse installations worldwide.

The resulting water quality is characterized by a low turbidity and SDI (silt density index) value. It is fed directly to the downstream RO installation, extending RO lifetime and reducing its associated operating costs. During ultrafiltration, backwashing is typically performed at fixed intervals, during which the flow direction in the membranes is reversed for a short period of time. This removes most of the suspended-solids layer that has built up on the feed side of the UF membrane. To improve backwash efficiency, it is recommended to follow with a forward flush to remove the suspended solids.

Reverse osmosis is a cross-flow filtration using high-pressure, spiral-wound fouling-resistant membranes. Water passes through the membrane, primarily by diffusing from one bonding site to another. For safe effluent reuse in the food industry, reverse osmosis is absolutely necessary to remove salts and potential viruses. To allow the reverse osmosis to operate in a stable manner, all suspended solids, colloidal material, and bacteria, must be removed upstream through ultrafiltration.

In the Farm Frites plant, backwash and concentrates from the membrane are recycled in the wastewater-treatment process, making the design even more unique. The process allows the recovery of 45,000 liters of safe drinking water each hour. De Watergroep, which is responsible for operation and maintenance  of the plant for 10 years, provides 24/7 monitoring.

Prior to implementing the Boomerang water-reuse solution, Farm Frites had been relying on groundwater and drinking water for its production process. For various reasons, those sources are no longer practical.

Fortunately for potato processors and others, today’s methods of wastewater reuse have become broadly accepted and economically feasible.

In fact, Waterleau leverages its water-reuse technology in its own Anaerobic Digestion R&D center, the Waterleau New Energy plant, located near Ypres, Belgium. There, all needed process water is recovered from digested waste streams by the company’s Boomerang technology.

With chemical oxygen demand and nitrogen levels close to zero, the recovered water—as clean as tap water—is used for cleaning, to feed the cooling tower, or for liquid-polymer preparation.

At full capacity, the potato-waste-fueled Waterleau New Energy plant near Ypres, Belgium, produces 3.2 MW of green electricity—equivalent to the energy needs for a city of 25,000 inhabitants.

Saving energy

Despite today’s lower oil prices and growing demand for waste products, anaerobic digestion is becoming a strategic and sustainable solution. While the technology has long been present in the brewery industry, the potato-processing industry has only recently begun to catch up.

The Waterleau New Energy plant itself is fueled by potato waste. Nearly 40% of the organic waste treated in the facility, i.e., potato peels, gray starch, french fries, and different fats, originates in the potato-processing industry. At full capacity, the site produces 3.2 MW of green electricity, which is equivalent to the energy needs for a city of 25,000 inhabitants.

Bottom line

Depending on the plant characteristics, bio-effluent recovery can be an effective way to reduce water intake and create clean energy, especially in food and beverage operations. Once the project characteristics have been assessed and the correct processing technologies are in place, sites can realize significant cost savings and operate more efficiently.

To date, Waterleau has built 30 wastewater and potato- waste-treatment plants. That’s because wastewater and potato waste have become major contributors to keeping energy bills under control. According to the company, as much as 60% of the power needs of a potato-processing plant can be recovered from anaerobic treatment of bio-effluent and potato waste. MT

For more information on Waterleau’s water and wastewater solutions, visit waterleau.com.