Treatment of different effluents with a single reagent

A leading European manufacturer of printed circuit boards wanted to improve the discharge of its wastewater, containing high concentrations of heavy metals. Its expertise is based on a unique know-how in Europe in design, industrialization, and manufacturing of sculpted Flex circuits. Its printed circuits are mainly specialized in the avionics and military fields. A printed circuit board, more commonly known as an electronic card, is a support that allows electronic components to be linked together. It is an assembly of thin layers of copper, etched by a chemical process, associated with an insulator. After these processes of metallization and engraving, the company carries out a rinsing by using city water. This washing water is therefore polluted and contains copper, nitrogen, and ammonia residues.


Ammonia, nitrogen, and COD concentrations are above regulations

Our client has two distinct types of discharge: a "metallic" discharge of about 20 m3/day and an "organic" discharge of 10 m3/day, at a constant rate of 24 hours a day, 5 days a week. Currently, our client has a treatment plant to treat the "metallic" discharge. Four liquid products are used in the treatment process: sodium bisulfite, a coagulant, a boron solution and a flocculant which must be prepared in solution. In spite of an apparently very complete process, the latter does not allow our Client to meet the discharge standards for its so-called "metallic" effluent, with regular exceedances for heavy metals, ammonia, nitrogen and COD values. In addition, the existing process does not allow the treatment of the so-called "organic" effluent. To do so, it must be stored and reprocessed by an external service provider.

A customized coagulant-flocculant formulation is made following the analysis of the samples received

Our Client decides to call upon the NISKAE team with the first objective of bringing the "metallic" effluent into compliance and, on the other hand, the possibility of treating the "organic" effluent. Once the samples of the two discharges were received, NISKAE experts could undertake a series of laboratory tests to develop a specially adapted coagulation-flocculation formulation. The so-called "metallic" waste has an initial pH value of 2.27. The first step of the treatment is therefore a neutralization of the pH by sodium hydroxide (NaOH). Subsequently, the addition of a decomplexing product and a custom-made flocculant simultaneously reduced the copper concentration from 188 mg/L to 0.10 mg/L and allowed a substantial reduction in the chemical oxygen demand, which will allow discharge into the natural environment. This coagulant-flocculant mono-reagent also significantly reduces iron from 3.71 mg/L to 0.21 mg/L and lead from 4.24 mg/L to 0.05 mg/L.

Laboratory tests carried out on the "organic" waste sample confirmed that no pH neutralization is necessary and that a single reagent can be used to treat both effluents, which can then be mixed in the same storage tanks. 
The advantage of the proposed process is a considerable simplification of the current treatment, with the reduction of the number of reagents, the reduction of dosages and the reduction of treatment times. The generated sludge is non-sticky and well dewaterable, which will allow a fast and uncomplicated filtration and gravity separation. The filtrate is clear and translucent and will be suitable for discharge.

A solution that reduces the use of reagents during the treatment!

Thanks to the NISKAE solution, our Customer will be able to use only two ready-to-use reagents which will allow the simultaneous treatment of the mixture of "metallic" and "organic" waste with a significant reduction of the quantity of heavy metals rejected. Less reagents, less sludge is as much more for the reduction of the risks for the operators.