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Since Cadbury, known worldwide as a chocolate and sweets manufacturer, took over the Dirol factory in Novgorod (located between St. Petersburg and Moscow) the amount of chewing gum produced has increased considerably to an average of around 200 m³ per day. Wastewater from the factory, up until now, had been treated at the local water company, but loadings and volumes were proving difficult and expensive to treat.
As a contribution to regional environment protection, and to coincide with Novogrod's 1000-year celebrations, Dirol Cadbury made the decision to build their own sewage treatment facility for processing chewing gum effluent. On account of the high content of polyol in the sewage, previously anaerobic treatment had been considered. However, tests with a BIOMEMBRAT® MBR pilot plant for a period of 3 months demonstrated that the effluent, in particular also the polyol, were very biodegradable by aerobic processes. Degrees of degradation of more than 90% could be reached.
Based on these results and the proven expertise of Wehrle's engineers, Dirol Cadbury placed an order with Wehrle in December 2008 for a large-scale MBR system. The process includes a balance tank, two bioreactors and an ultrafiltration membrane system to separate the treated biomass. Also included is mechanical pretreatment, sludge dewatering and an activated carbon adsorber for post-treatment of the biologically cleaned wastewater. This additional treatment is necessary if the inflow CSB concentration exceeds 8,000 mg/l, so the outflow CSB concentration specification of 200 mg/l can be met.
Wehrle designed the treatment facility, delivered all technical components, supervised installation and undertook commissioning and optimisation.
Author: Cornelia Timm
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