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Turning organic wastewater into biogas

Biowater’s HyVAB® technology: Food manufacturer builds wastewater treatment plant which turns dissolved and suspended organics into combustible gas. The new compact and highly effective treatment reduces the sludge production to a historic minimum.

Norwegian food manufacturer Smaken av Grimstad (SAG) processes 8.500 tonnes of vegetables per year into food products and is steadily increasing its production volume. The production facility generates a large volume of wastewater, that originates from vegetable cleaning prior to processing.

Until recently the wastewater has been treated off-site at the local municipal wastewater plant (Groos RA), however this plant is working at maximum load, especially during vegetable harvest season. Recently SAG hired Biowater to come up with a modern wastewater treatment process to take care of the effluents.

Picture: The wastewater treatment plant at SAG is highly compact. A striking feature is the biological process tower, where the organics of the wastewater is turned into combustible methane gas.

Green
Biowater’s patented process Hyvab® is now up and running, and reducing the load from SAG to the municipal plant by 90%. An extra benefit from the Hyvab® process is the production of methane gas, which will be used for heating purposes at SAG.

"We have for a long time been concerned about the capacity of the municipal wastewater treatment plant. To be able to increase our production we needed to make a move. We knew Biowater had done a lot of work with wastewater for the food industry. After discussing our case with Biowater we concluded that to build our own treatment plant would be the right thing,” states managing director of SAG, Mr. Jan Rommetveit.

The Biowater process was preferred for two main reasons. The process is completely biological and requires no flocculants of coagulants to work. Secondly a considerable proportion of the organics in the wastewater is transformed into methane gas. “The Biowater process is cheap to run, and we already pay for energy, so we expect to save some there,” states Mr. Rommetveit.

Facts and figures
• Maximum load of wastewater plant:  23 m3/hour
• Producing 260 days of the year will yield energy equal to 1.047.695 kWh
• Average KOF load 2600 mg/liter
• Energy from m3 treated water 7,3 kWt/m3

 

Agreement
Before SAG decided to spend 10 mill NOK on the new wastewater treatment there was a need for an agreement with the municipalities about the division of tasks. Through a constructive dialogue with the municipalities an agreement was quickly settled, all in accordance with the urgent needs of SAG and the legislative authority of the local municipality of the city of Grimstad.

«The wastewater plant will give us more freedom to increase production and the municipalities will have more free capacity at their plant, this is a win-win situation for both of us,» states Mr. Rommetveit.
The wastewater plant is of traditional design, however the difference lies in the biological process, which is taken to a new level. Besides producing methane gas, the plant generates a minimum of sludge, generating a minimum of transport costs.

«We see this as a good example of sustainable solutions and seems like the right way to go for the food manufacturing industry», states Mr. Rommetveit.

Reactor
Up until recently the wastewater from SAG into the municipal system has been the equivalent of approximately 10 000 persons (p.e.).

«The new wastewater plant is a great step forward for us, since we do not need to apply for a new environmental certification, we may expand freely,» Mr. Rommetveit explains.
Since the biological reactor is based on live biocultures, and production of wastewater highly variable, a buffer tank of 600 000 liters of wastewater was necessary. This will ensure a steady volume of wastewater entering the reactors and makes it possible to adjust the pH in the wastewater prior to the process.
 

Biological in two steps
The wastewater treatment process has been developed by Biowater, with support from The Norwegian Research Council and Innovation Norway. The heart of the process is a 14 meter high «reactor-tower».
  • In the bottom of the reactor (the first step) is an anaerobic biological reactor, where 75% of the organic waste is converted into methane gas.
  • At the top level of the tower is a new type of aerated biofilm reactor that consumes the remaining organics and odorous gases that emerge.