Project Details

Project Delivery

Project Results

Discussion

Situation

A German delicatessen company specialising in Mediterranean antipasti processes southern European fruit and German cream cheese into high-quality, preserved snacks that are available in numerous supermarkets. The raw ingredients are mainly sourced from southern European countries and arrive at the production facility either dried or preserved in brine. The ingredients must be thoroughly rinsed before further processing. In combination with the regular hygiene wash cycles, the company produces up to 75 cubic metres of wastewater per day.

Problem

Due to the processing steps and ingredients used – including oils, emulsifiers, soaps and disinfectants – the wastewater is heavily contaminated organically. The chemical oxygen demand (COD) is around 15,000 mg/l and the biological oxygen demand (BOD5) is around 8,500 mg/l. Due to this high organic load, the company was not permitted to discharge the wastewater directly into the municipal sewage treatment plant. Instead, the wastewater had to be transported away at great expense and treated externally, which resulted in high costs. The company therefore looked for its own wastewater treatment solution.

An initial trial with membrane filtration did not bring any significant improvement. Three wastewater samples were therefore taken for analyses at different production stages: Raw wastewater, after grease separation and after membrane treatment. The samples were analysed by the PPU’s in-house laboratory. They showed good suitability for biological wastewater treatment.

Solution

The ideal solution for wastewater treatment in the food industry is the combination of ClearFox® FBBR and ClearFox® DAF technologies.

Coarse screening and initial biological-mechanical pre-treatment

The wastewater first passes through a screening unit that filters out solids such as peel residues and pips. It is then stored in aerated plastic tanks to equalise peaks in the inflow and ensure good mixing. The aeration also supports the initial biodegradation of the organic substances.

Separation of undissolved substances with ClearFox® DAF

After pre-treatment, the wastewater enters the ClearFox® DAF, which removes the finest suspended solids by pressure release. The wastewater is supersaturated with air, which dissolves again in tiny bubbles as soon as it enters the flotation reactor. The suspended solids are carried to the surface by the rising bubbles and removed from the system through a special conical opening. The wastewater in the lower part of the reactor remains nearly free of suspended solids and is passed on to the fixed-bed reactor.

Biological wastewater treatment in the fixed-bed reactor (ClearFox® FBBR)

Dissolved organic substances are broken down in the fixed-bed reactor. The special material in the reactor offers microorganisms an optimal surface for colonisation. The microorganisms respire the organic substances under oxygen supply. Dead microorganisms sink to the bottom and form secondary sludge, which is separated from the treated wastewater using a lamella clarifier.

Sludge dewatering and storage

The sludge produced by the ClearFox® DAF and the fixed-bed reactor only contains a low dry matter content of two to three per cent. A modern sludge press increases the dry matter content to 35 to 40 per cent so that the sludge can be stored and transported away in a stable manner.

Construction and operation of the plant

The entire wastewater treatment plant comprises six 40-foot containers, five buffer tanks and a screw screen. Four containers contain the fixed-bed reactors and the lamella clarifier, while the dissolved air flotation and the sludge press are located in two other containers. The plant has been in operation since October 2024 and ensures efficient wastewater treatment for indirect discharge.