Operation and Control of a Full‐Scale Biogas Plant Treating Wastewater from the Cleaning of Car Tanks

A 1200‐m3 full‐scale biogas plant treating highly polluted wastewater (WW) from the cleaning of tank cars transporting food and fodder is working stably and efficiently despite the WW is constantly varying in strength and composition, is easily acidifying, and low in alkalinity. Na2CO3 has to be added to maintain the digester alkalinity and the digester pH at defined values due to softened water used for car tank cleaning. Monitoring volatile organic acid concentration and controlling the alkalinity in the digester are essential for maintaining the digestion process stability. Biogas production is adapted to the demand by a modulated feeding regime. The drastic modulation of feeding is possible due to the moderate organic loading of the plant along with the high average hydraulic retention time. A 1200‐m3 full‐scale biogas plant is working stably as planned for treating highly polluted wastewater from the cleaning of car tanks transporting food and fodder. For stabilizing the digestion process, Na2CO3 is regularly added to avoid an insufficient alkalinity in the plant. For monitoring and controlling of the plant, volatile organic acid and alkalinity have to be measured.