Sustainable wastewater treatment with proven results
After one year of operation, the new wastewater treatment plant at Smaken av Grimstad, has both solved challenges and opened up new opportunities. The treatment process is sustainable; it produces heat, minimal sludge and a treated wastewater with great potential for reuse.
By: Tommy Charles Olsen for Biowater
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The Smaken av Grimstad processing facility in Southern Norway produces over 40 varieties of fruit and vegetable products. In 2016, the facility increased production and by consequence wastewater volumes, which come from the washing of the natural ingredients. Even with a significant reduction in water consumption achieved over the previous 5 years, wastewater from the facility had long been to the point of bursting for the local municipal wastewater treatment plant. Last year, therefore, Smaken av Grimstad decided to build its own treatment plant, which has now solved the problem. The solution is sustainable and environmentally friendly, and at the same time has softened the municipality’s challenges.
“The results are beyond expectations. The plant works well and gives us an energy surplus in the form of heat, which we will eventually utilize to our advantage. The process is so efficient that it also allows for reuse of water” says quality manager Sigmund Leiros of Smaken av Grimstad.
Picture: Good operational overview via the control panel. L-R Quality manager Sigmund Leiros from Smaken av Grimstad, Ilya Savva from Biowater Technology and General Manager Jan Rommetveit from Smaken av Grimstad.
Processes that utilise organic waste to make biogas are not new, but doing so with industrial wastewater is more complicated. The quality of wastewater varies significantly, so often technology becomes more complex to meet the discharge requirements. The solution for Smaken of Grimstad has therefore been followed with great interest in the Norwegian food industry.
While traditional treatment plants require a lot of space, consume chemicals and produce a lot of sludge, this process is the opposite. It takes up little space and utilizes the wastewater resources in a direct way. The heart of the plant is a standing tank of methane producing bacteria, which lives off the wastewater. The bacteria consume the organic compounds in the water, which is fed from a buffer tank to ensure great tolerance for flow variation. The biological process requires no chemicals, but pH is adjusted slightly prior to treatment.
“What makes the method so exciting is that approx. 75% of the organic waste goes directly into methane gas, which can be directly utilized as an energy source, says Engineering Manager, Ilya Savva of Biowater Technology in Tønsberg. At the top of the tank, the process ends with an aerated biofilm plant, which removes residues of organic matter and any odours.
A smart feature of the solution is that sludge from top part falls back into the first part of the plant for digestion, contributing to stable operation, less sludge in the output and high gas production. In addition, the biological step can be run at different stages, depending on the amount of strain. It can be run with periodic sludge removal when necessary.
“The plant provides combustible methane and, in total, a positive energy contribution. Using the gas for heating is the next goal for us”, says Leiros. An important feature of the process is that the effluent contains few particles, low dissolved substances, and it provides virtually no sludge. A historical issue are the strict requirements for handling sludge, which is technically demanding to process and often associated with huge costs to get rid of.
“That we have exchanged sludge of gas therefore gives double gains,” Leiros emphasizes. Processing fruit and vegetables requires a lot of water. The fact that the treated water is of good quality allows now for further gains through water recycling with membrane technology.
During a recent week of sampling, the results showed that the plant gave a reduction of 90.4% of the total chemical oxygen demand (COD) in the wastewater. At the same time, the reduction of dissolved substances was 91.2%. Wastewater contains, as previous analyzes indicated 250-850 total COD kg/day.
“We had a goal of a reduction of 86% total COD, so it’s been a real bonus to have achieved so much better results. It has also given us more biogas than expected as well cleaner effluent water,“ points out Savva.
On the energy side there is also good news. Since the plant requires far less supply of air than other treatment systems, and has few mechanical components, it consumes less energy, approx. 1 kWh per cubic meter of treated water. The gas production in the plant is stable and approx. 0.4 cubic meters of methane per kg reduced COD. In summary, the process contributes to a net positive contribution in the energy accounts. Wastewater was previously handled uncleaned by municipal wastewater treatment plant (Groos RA), and now has a much less strain. Without the measure, the treatment plant at Groos would have had to be have been extended.
The resort has cost approx. £1.3 million to build and has received support from Enova, a public organisation in Norway which supports projects to develop future energy systems and reduce greenhouse gases. According to Biowater, the process, which has been named HyVAB*, is specifically tailored to wastewater from the food industry, pharmaceuticals and municipal plants. The benefit, including treated water quality and the amount of gas you can count on will depend on the composition of the wastewater, but can be simply assessed by their expert team.
*Hybrid Vertical Anaerobic Biofilm.