Kaliko GmbH in Bamberg, North Bavaria, has successfully operated in the textile finishing sector for more than 135 years. Their range of products includes textile fabrics for book covers or roller blinds and various technical textiles. Especially in the field of fabrics for roller blinds, Kaliko GmbH is among the leading producers worldwide. Kaliko GmbH is known for eco-friendly finishing processes without the use of solvent-containing materials, chlorine, CFC, brominated flame retardants or PVC. Due to the high water consumption for textile finishing they want to internally recycle the generated process water. A requirement is that the quality of the treated wastewater does not negatively influence later dyeing processes.

In view of the production-dependent, strongly varying wastewater composition pilot tests on a technical scale were carried out before full-scale planning and installation of the plants. On the basis of these pilot tests, project-specific conditions were identified to ensure the reliable operation of the plants.

Plant start-up and operating results

In September 2008, the HDF-10 flotation plant was the first machine that was put into operation. With the use of special precipitation chemicals and neutralisation, the flotation plant is able to efficiently clarify the wastewater flow. The COD reduction achieved reliably exceeds 50%. The solids and colloids contained within the wastewater are removed and along with the excess sludge directly passed to the customer's belt filter press to be dewatered.

The complete removal of colorants is unreasonable both ecologically and economically due to the strongly varying concentration of their ingredients because a disproportionately high amount of chemicals would have to be applied.

Since start-up of the two VRM® 30/240 units in October 2008, the treated wastewater with a COD concentration of 900 - 4500 mg/l is directly introduced into the downstream MBR. The biological treatment stage is operated with a DS concentration of approx. 8 g/l and achieves a constantly satisfying permeate quality with < 5 mg/l BOD₅. A residual COD content of approx. 160 mg/l remains within the permeate and can be considered as inert.

The stability of the whole system has been proven by the fact that chemical purification has become necessary only two times by now. In view of such a complex wastewater matrix, this is evidence of the outstanding sturdiness of the treatment system applied.

About 80% of the permeate produced by the HUBER equipment can directly be reused in the process. Due to the optimized application of chemical auxiliary substances and energy-optimized equipment units the payback period will probably be even shorter than the initial target of five years.