Potato Processing at Friweika Germany
Next to processed products the potato can serve as an energy supply. This is what Friweika eG, a potato processing business in Weidensdorf (Germany), is exemplary in demonstrating. When production surges, proper cleaning of the ever-increasing amounts of wastewater must be maintained according to regulations. Specialists of the Dresden (Germany) based DAS Environmental Expert GmbH (DAS EE) have mastered the necessary expansion of the aerobic biological wastewater treatment innovatively with minimum spacial requirements.
Increasing Amounts of Wastewater
For Friweika, potato processing and marketing are basically booming all year round. Through the integrated and optimum use of resources the company even produces energy from waste products, enabling them also to cover a large amount of their heating demands through their own biogas production. Even the accrued process wastewaters are used for energy production before they are fed into the biological wastewater treatment system.
Since its commissioning nine years ago the aerobic biological stage of wastewater treatment has been expanded several times. This is due to continuous increases in production and its related surge in pollution levels of wastewaters. However, after increasing aeration, expanding the hydraulic capacity and increasing its overall automation level, the original four-step combination compact system, with each step consisting of a sludge tank with a plunged packed bed and integrated secondary sedimentation basin, reached its capacity.
Considering the production expansion and the expected increase in organic load also in the discharge water from the existing treatment plant, Friweika needed to extend the aerobic treatment by adding an additional new system. The old system was originally designed to handle COD loads of 560 kg/d, and was filled far beyond its capacity with loads at times reaching 1260 kg/d.
But the question was, where to put the additional system? A new plant would have required a second round, 22 meters in diameter and a 6 meters high combination tank, for which the company simply did not have the space.
This is where the DAS EE specialists came in and worked out an innovative and highly effective solution. Instead of adding another compact system, they integrated a TFR-reactor, the core product of DAS EE wastewater technology, into the plant concept, and achieved, compared to a classic system, a reduction of spacial requirements by nearly 50 %. The new concept convinced the plant operators at Friweika.
Construction and commissioning of the new system happened without significant interruptions in the operation of the pre-existing treatment plant.
Extending the Wastewater Treatment Plant Instead of New Building
Instead of a new building DAS EE specialists suggested to simply extend the old system by adding 4 reactors of the type TFR industrial, each 3 meters in diameter and 8 meters high. Extensive pilot trials convinced Friweika of the system’s treatment capacity, which is why in the end the company chose DAS technology.
DAS technology offers several advantages at once. One is the system’s aforementioned small footprint. The reactors contain a lightweight carrier material with a highly specific surface. Microorganisms growing a biofilm on the carrier material cause the aerobic degradation, thus taking advantage of the high capacity in wastewater treatment that the biofilm process is known for.
The reactor, operating by the counter current principle:
- The wastewater trickles down as a liquid film.
- Ventilators push air in the opposite direction creating highly effective substance
exchange conditions ensuring the continuous supply of oxygen necessary for the microorganisms in the biofilm as they perform the aerobic degradation.
TFR technology is based on the ‘philosophy of modular design’ and can quickly and easily be extended by adding additional reactors without requiring work-intensive construction.
In classic activated sludge tanks the microorganism’s supply of oxygen is achieved by aerating deep tanks from the bottom against a water column of 8 m or higher. Pressure loss against the carrier material on the other hand is merely 30 cm (300 mbar). Thus, the TFR reactor needs significantly less energy for oxygen supply – an additional advantage of the DAS technology.
Reliable and Effective
At Friweika, the 4 TFR reactors have been operating since August 08, 2012. The wastewater stream is separated into two parts with one being treated by the old system and the other one in the TFR reactors. Part of the wastewater treated by the old system is used to re-fill the TFR reactors after removing excess biofilm, which becomes necessary from time to time. Together the two systems have a treatment power that has not yet reached its capacity even during production expansions, as the past couple of months have explicitly revealed. At design-conform operation the wastewater with inflow COD loads of about 3,500 mg/l (85 % percentile) was cleaned to indirect discharger quality with TFR reactor outlets containing less than 1,000 mg/l COD.