A circular filtration solution to tackle WWTP emissions

• Incoming streams from manufacturers: if the outlet stream of wastewater contains pollutants with concentrations above the WWTP’s acceptance level - which is the maximum concentration that a WWTP is legally permitted to admit - the producer needs to lower these concentrations. Therefore, a pre-treatment is needed before the stream can be accepted by the WWTP;
• Effluents: before being discharged, the treated wastewater might need to be subjected to a polishing step to lower the pollutants concentration even more. This is the case of a plant discharging their wastewater into a nearby river as it must comply with strict emission limits, or treating wastewater before reusing it for its operations. Another example could be odour removal following neighbours’ complaints.

The EU legislation recommends activated carbon as one of the best available technologies (BAT) to treat a wide range of pollutants contained in wastewater and air emissions. In addition to this, based on numerous successful projects over the years, DESOTEC has proved the effectiveness of activated carbon at removing all the contaminants mentioned above. To add to that, DESOTEC also has the expertise to select the most suitable activated carbon grade/mobile filter type combination to optimise WWTPs purification system. 

Here are some of the advantages entailed by DESOTEC mobile filtration solutions:

• No CAPEX & lower cost: Buying a fixed filter implies a greater upfront investment (i.e., capital expenditure (CAPEX)) vs renting a mobile unit. In addition to this, fixed installations might no longer be suitable following production variations, contamination changes, or regulation upgrades. This implies purchasing another unit along the line, thus translating into further expenses.
• Greater flexibility: Tapping into a modular system will let plants purify their emissions while spending less money. All it takes is to add more mobile filters as needed. Moreover, DESOTEC’s plug & play mobile units can work either as a pre-treatment or polishing step downstream of the WWTP.
• Less downtime: Once saturated, the spent carbon needs to be vacuum extracted and the filter to be refilled with fresh carbon. While the exchange process of mobile filters takes just 30 minutes - as the whole mobile filter is replaced by a new one, with no onsite waste carbon handling - the carbon replacement of fixed installations is likely to take two workers up to multiple days, a costly downtime that many can’t afford. Furthermore, after being taken back, the exhausted mobile filter will be checked, thus not wasting any production time for maintenance purposes.
• More safety: Besides saving money, the off-site emptying of mobile units is also safer as it prevents operators from being exposed to hazardous waste and dust. 

COD removal for the textile industry

Following an increase in production and changes in the manufacturing process, a client's biological WWTP was no longer sufficient to keep COD levels below emission limits (120 mg/l). After the customer reached out to us, DESOTEC ran a pilot test to begin with. These helped choose the best solution for their purification needs: 2 MOBICON 2000 filters in series filled with ORGANOSORB 10-AA. Once the filters went live, the plant became compliant again. 

AOX removal in the automotive industry

Following an upgrade of environmental regulations, a WWTP in Portugal was no longer able to ensure compliance with the stricter AOX emission limit (0.4 mg/l)​. The plant manager contacted DESOTEC and asked for a rapid solution. As the contaminated flow (9 m3/h) contained suspended solids (80 mg/l), DESOTEC installed 1 MOBICON 2000 as a pre-treatment. Downstream of that, 1 MOBICON packed with ORGANOSOB Plus was dedicated to the removal of AOX.

Removing surfactants from wastewater at a chemical company site

Because of an unexpected presence of surfactants (ca. 20 mg/l) in the wastewater of a chemical company, foam formed in the oxidation tank of the treatment plant. Furthermore, the surfactant level was above the concentration that could be accepted by WWTP, meaning the company had to stop production until it found a solution. This was an emergency scenario and the customer required a prompt solution. DESOTEC immediately delivered and installed 1 MOBICON filter packed with ORGANOSORB 10 AA. As a result, the surfactant level met the acceptance limit from the WWTP and production resumed within 48 hours.

Removing PFAS from water at a waste management site

A WWTPs manager reached out to DESOTEC to reduce the PFAS level in their wastewater from 732 µg/l to the drinking water limit (100 ng/l). DESOTEC installed two filters in series: the first one to remove COD and larger PFAS molecules; the second one to adsorb smaller PFAS molecules such as perfluorobutanoate (PFBA), perfluorobutanesulfonic acid (PFBS) and trifluoroacetate (TFA). After implementing this two-step solution, the customer became compliant with the drinking water regulation. 

Tackling odour nuisance in air emissions from WWTP

A WWTP in the Netherlands received odour complaints from neighbours. Therefore, it needed to treat air emissions from the hall ventilation (high flow, low concentration of sulfuric components) as well as those coming from sludge mixing and storage (low flow, high concentration of inorganic compounds).

For the hall ventilation, a DESOTEC AIRCON filter was enough to treat the odorous components. As concerns sludge mixing and storage units, a two-step filtration process was put in place: a) biofilter for ammonia removal; b) another AIRCON filter to remove remaining odours.

Thanks to our intervention, the plant stopped receiving any complaints from neighbours, and could continue to operate smoothly.