A company from Slovenia has specialised in processing vegetables. This produces about five cubic metres of wastewater per day, which the company used to discharge into a municipal Chemical Wastewater Treatment plant. However, since the wastewater is very acidic (pH 3.5), the company asked for a treatment solution to be able to discharge it directly. The goal was for the company to build a fining pond in which the wastewater could percolate.
Due to the balanced ratio between COD and BOD5, a biological treatment of the wastewater was suitable for this project. The ClearFox® team developed a plant concept consisting of screening, dissolved air flotation with pH adjustment and a fixed-bed biological reactor. The screening first removes all solids from the wastewater that are not allowed to enter the DAF or the FBBR. These are all solids larger than three millimetres, as otherwise blockages can occur. In the second step, a neutralisation plant adjusts the pH value. The Slovenian government prescribes a neutral pH value between 6.5 and 9.5 for direct discharge. Afterwards, biological treatment takes place using a fixed-bed reactor.
This should be installed underground in plastic tanks. Afterwards, the treated wastewater flows into the fining pond. The ClearFox® DAF should be installed exactly where the Wastewater Treatment Construction is produced. As the customer wanted to carry out the installation and commissioning himself, he received comprehensive training from the ClearFox® team at the main factory in Bayreuth. The focus was on the DAF, the mixing section, and the control technology.The combination of screening, ClearFox® DAF and ClearFox® FBBR is an outstanding solution to ensure direct discharge of the wastewater according to the customer’s wishes. Dissolved air flotation removes up to 99 per cent of non-dissolved matter and discharges it as sludge.
The first challenge in this project was the pollution parameters and the required discharge values. The wastewater was not only acidic, it also had a very high COD of about 52,000 mg/l and a high BOD5 of about 26,000 mg/l. In addition, vegetable residues are always mixed into the Municipal Sewage System, which must not enter the treatment plant. Therefore, a multi-stage treatment is necessary to achieve all required discharge values.
The second challenge was the space available on the company’s premises. One part of the treatment plant was to be integrated directly into the production process, the second part was to be installed underground. Therefore, the plant had to be designed in such a way that maintenance work was kept to an absolute minimum. In addition, the customer wanted to be able to install and commission the plant himself.