Zur Schlußreinigung konzentrierter Zuckerfabrikabwässer

The most important measure is that the freshwater demand of 0.5 m³ per t beet processing is strictly kept to or fallen below, to which a catalogue of measures with ten points is presented. The wastewaters which cannot be used again have to be stored prior to the final purification in order to compensate for quantities and concentrations, aerated storage ponds being successful for small sugar factories as the purification technology. For this, three cases are described as examples: supplementary equipment of two anaerobic ponds with a rod-roll aeration, by which within two months (May to July) the BOD₃ is reduced from 1,200 to 11 mg/l. The aeration of a pond of 12.5 ha (370,000 … 500,000 m³) by means of a centrifugal aerator (45 kW) does not lead to completely aerobic conditions: Accumulation up to 350 t BOD₅, 200 t organic acids at a reduction of 100 t sulphate, 45 t of which being converted via sulphides by photoautotrophic sulphur bacteria. This combination of anaerobic and aerobic processes is very economical. At aeration with ca. 1 W/m³ in the third case in summer there are achieved wastewater loads which are of a receiving-water quality.