Well Water Treatment and Water Saving Through Water Reuse

Cause

A textile finishing company commissioned WEIL Wasseraufbereitung to design and construct a process water treatment unit. The existing softening system based on ion exchangers was to be replaced by desalination using reverse osmosis. The background to this was an official requirement limiting the chloride load and concentration in the wastewater. Due to the limited well water withdrawal quantities, the yield of reverse osmosis was to be around 90 %. The well water had silicate concentrations of approx. 25 m/l and a total hardness of approx. 23 °dH. This challenging task was solved by a multi-stage membrane system with a module configuration adapted to the raw water, antiscalant dosing and an intelligent control and rinsing concept. The system is operated with yields of between 87 and 89%.

Process water treatment with concentrate reuse

WEIL Wasseraufbereitung installed two reverse osmosis systems, each with a permeate capacity of 30 m³/h, for process water treatment.

Until the chloride discharge value was tightened, the reverse osmosis was preceded by softening using an ion exchanger. This is usually used to avoid additional antiscalants. In this case, however, the chloride load of the process water, and therefore the wastewater, was too high. For this reason, the system was switched to operation with antiscalant, which resulted in compliance with the limit values.

In order to reduce the water withdrawal from the local wells, a nanofiltration stage was installed to treat and reuse the saline concentrate produced during reverse osmosis. This increased the overall yield of the water treatment system to 87%.