Wastewater treatment for a wood processing company
ClearFox® FBBR for wastewater treatment in a wood processing company
A company from southern Germany has focussed on the processing of wood. Facades, furniture, and customised interior construction projects are produced at several locations in Germany and Switzerland. The company was planning its own wastewater treatment system for the main production site so that it could be discharged directly into the environment.
An engineering office, which was to realise the order, asked PPU Umwelttechnik GmbH for a compact solution. The wastewater comes from four sources: Firstly, the employees produce around 2.25 m³ of sewage every day. Secondly, condensate is produced during the various drying processes. This is around 9 m³ from the sawn timber dryer and around 9 and 7 m³ from various chip dryers.
The first challenge in this project was the composition of the condensate. This consists mainly of formic acid (500 mg/l), acetic acid (400 mg/l) and methanol (30 mg/l). In addition, there are trace substances of tannic acid, pyrogallol, essential oils and unsaturated hydrocarbons. As these are not biodegradable, they only influence the COD, which, with the addition of sewage, is around 950 mg/litre. The pH value fluctuates between 5 and 7.
The target for direct discharge is discharge class N. This is defined by a COD of 90 mg/litre, a BOD5 of 20 mg/litre and an ammonium content of 10 mg/litre. The decisive factor here is the ammonium. If the concentration is too high, it harms many aquatic plants and animals. Special bacteria are therefore used to convert the ammonium into less harmful nitrogen – the so-called nitrification.
The ideal solution for this project was a ClearFox® containerised wastewater treatment plant with fixed bed technology. The wastewater first flows together from the various sub-streams in a buffer tank. This is a plastic tank installed below ground, which also equalises the inflow peaks. The wastewater then flows through a mixing section, which equalises the pH value. This is necessary for the subsequent biological treatment to be effective. The fixed-bed reactor consists of growth bodies for microorganisms that respire the contaminants in the wastewater. This produces a sludge, which is subsequently separated from the clear water by a lamella clarifier.
The ClearFox® containerised wastewater treatment plant impresses above all with its compactness. Thanks to its small footprint, it can be installed on the company premises and can discharge the treated wastewater directly into a nearby river. As the wastewater treatment plant was produced and tested as a turnkey solution at the main plant in Bayreuth, the delivery, installation, commissioning, and employee training was limited to just one day.