Das Projekt "Behandlung des Abwassers aus einer Kartoffelverarbeitungsfabrik mittels einer kombinierten, vier Schritte umfassenden anaeroben Technologie mit stationaerem biologischem Rasen" wird vom Umweltbundesamt gefördert und von Convent Knabber-Gebäck GmbH and Co. KG durchgeführt. Objective: The project aims to demonstrate a full scale plant for the biological treatment of wastewater originating from a potato-processing factory, including an anaerobic stationary fixed film methane digester and a finition aerobic treatment system. Innovative is the energy saving through the recycling of waste energy of the potato-processing factory to heat the wastewater to be treated, the full-scale stationary fixed-film process and the biogas recovered from it, and, hence, the lower energy consumption by the aerobic treatment. The wastewater treatment plant will be installed in the Company Convent, Knaber Gebaeck, GmbH and Co, Frankenthal. The expected energy production is 170 TOE per year. The simple payback period is estimated at 2 years by comparison with an alternative conventional solution. General Information: The methane digester, central place of the potato-processing wastewater treatment system is a stationary fixed film reactor of 1400 m3 capacity containing 1000 m3 of plastic material as carrier with a specific surface of 150 m2 per m3. The running conditions are the following: mean hydraulic residence time 2 to 2.5 days, loading rate from 1.5 to 3 kg COD per m3 of digester working volume and per day, temperature of the mixed liquor between 35 and 37 degree of Celsius. The expected performances are the following: 85 per cent conversion in the anaerobic step on a COD basis, a yield of 0.8 m3 biogas per m3 wastewater treated, excess sludge production amounting to 7 per cent of the excess sludge produced in a similar aerobic system, a biogas production rate of 1440 m3 per day. Upstream of the methane digester, 700 m3 wastewater per day, with a COD of 6 g/l, are sieved through trommel-type sieve, heated from 25 degree of Celsius to 40 degree of Celsius in a heat exchanger, and led to step l of the system: a buffering tank of 1000 m3where acidogenesis and acidification take place. Downstream of the methane digester, the wastewater being treated is led to an aerobic fixed film trickling filter of 200 m3 capacity filled with plastic carrier, at a loading rate of 2 kg BOD per m3 reactor per day, at a superficial velocity of 2 m/h, a temperature of 30 degree of Celsius. The conversion is expected at 15 per cent of the initial COD content. The effluent is filtered on a filter and the collected sludge recycled upstream. The liquid is led to a 1000 m3 aerobic tank at a low loading rate of 0.2 kg BOD per m3 reactor per day, a long mean residence time and a food to micro organism ratio of 0.06 kg BOD per kg suspended matter per day. The effluent passes through a conventional decanter before being disposed off. The sedimented sludge is recycled upstream. The demonstration project relies on a 3 year preliminary study conducted by the University of Hanover using pilot plants of 1 m3 and 13 m3 one year each. The monitoring will be effected by the University of Hanover and consists of a follow-up to the start-up. During an 18 months operatio