Reducing waste water contamination in plastic recycling

Recovering and recycling plastic is crucial for achieving sustainability goals – but the process creates its own environmental problems in the form of contaminated wastewater.  

DESOTEC’s MOBICON filters are ideal for purifying wastewater so that it meets legal requirements, enabling recycling plants to grow their business and keep plastic waste out of landfill.

The problem

Our client, based in the Italian market, recovers and recycles plastic boxes, mainly from the food industry.

During the washing and recycling processes, food residue and cleaning agent pollutants are produced. Before the wastewater can be sent off-site for further treatment, the level of these contaminants needs to be reduced.

If left untreated, the COD concentrations in the wastewater from this plant are around 600 mg/L. The legal limit in the region is set at 500 mg/L. Due to the client’s strong commitment to principles of environmental sustainability and corporate social responsibility, it has set itself a lower COD limit of just 200 mg/L.

Up until recently, the client was able to filter the pollutants from the wastewater itself using fixed carbon filters. However, earlier in 2019, it increased its rate of production and found that its filters were unable to cope. COD levels were higher than expected, and the client was unable to ascertain the cause.

Aware that the core expertise of the business was in recycling plastic, not purifying wastewater, the client called in DESOTEC.

The solution

DESOTEC engineers first visited the site in July 2019 to help the client investigate why the existing filters were no longer working correctly. They found that suspended solids in the water were clogging the carbon filter. This reduced their efficiency and made it harder to pump water over it. Working closely with the client, DESOTEC designed a solution that involves a two-stage filtering process.

The client’s existing filter was converted to use sand, which filters out the suspended solids from the wastewater.

Then a MOBICON filter was installed, which uses activated carbon technology to filter the water for a second time, treating the remaining organic compounds to reduce the COD levels.

As the MOBICON filter is supplied on a rental basis, this did not require major investment on the part of the client.

The MOBICON was in place within just a few weeks of DESOTEC’s first site visit, and the filter was exchanged for the first time at the end of August.

The results

The new system has proved to be a great success.

COD levels after purification are 150 mg/L – well below the legal limits, and also comfortably within the lower limit set by the client.

Filters are exchanged on average once a month. It takes the client around one hour to disconnect the old filter and reconnect a new one, with DESOTEC removing the spent filter to its own site for further treatment.  

That means the client does not need to cease operations for long to allow for the exchange to take place. Nor do any of the client’s employees need to handle the spent carbon themselves.

The client has expressed great satisfaction with its partnership with DESOTEC, praising our reliability, promptness and continual support.

There is a named DESOTEC account handler who is in daily contact with the client. Results and weekly analyses are shared so that DESOTEC experts can consistently check that the filter continues to operate at optimum efficiency. 

With an effective wastewater management solution in place, the plant is able to cope with existing business and scale up when they need to.

Sales teams are now being given the green light to approach potential new clients, thus growing the business and contributing further to the conservation of the earth’s resources.

Contact DESOTEC today

Our client is a model for other plastic food packaging companies in the Italian market and beyond who wish to reduce contamination in their plastic recycling processes.

While this particular customer does not have a huge problem with surfactants, other plants in the Italian plastic food packaging market do – and legal limits are strict, often as low as 10 mg/L. DESOTEC’s mobile filters can treat these surfactants successfully, too.

As the MOBICON filters are available to rent on a monthly basis, they require no major investment from clients.

To find out how DESOTEC’s series of mobile filters can help your business deal with contaminated wastewater, contact us today.


At DESOTEC’s facilities, all used carbon is analysed so the right measures can be taken for handling and removing the saturated carbon out of the mobile filters. All molecules that were adsorbed on the activated carbon at the customers’ site, are desorbed inside DESOTEC’s reactivation furnaces. These contaminants are then fully destroyed, in accordance with National and European legislationby an incineration and neutralisation setup. The entire installation and it's emissions are under continuous on-line monitoring, which guarantees that only harmless water vapour is seen exiting the chimney.