Der Arbeitskreis konzentriert sich auf die Förderung von nachhaltigen Konzepten und Technologien zur Ressourcen- und energieeffizienten Wasser-, Abwasser und Teilstrombehandlung, wobei hier die Themen Wasser- und Wertstoffrecycling, Energie aus (Ab-)Wasser sowie die Optimierung des Betriebsmittelverbrauch und Lebenszykluskosten im Vordergrund stehen. Zudem tauscht sich der Arbeitskreis über neue Produkte und Dienstleistungen im Bereich Automatisierung und Digitalisierung aus, erörtert Einspar- und Verbesserungspotentiale durch Standardisierung und Modularisierung, Vorteile der Nutzung von Technologie zur Spurenstoffelimination sowie der Schlamm- und Reststoffbehandlung.
Die Mitglieder von GWP kommen aus allen Bereichen der Wasserwirtschaft und bringen eine hohe Kompetenz mit. Die Ziele dieses Arbeitskreises sind die Bündelung und Abstimmung von gemeinsamen Themen und Interessen der Mitglieder im Hinblick Ausrichtung auf Industriekunden.
Die Ziele im Überblick:
12/2019 Tirupur, India
Dying processes require high concentrations of salt to fix the dyes onto the cellulose textile. At the end of the dying process, the wastewater stream consists of a high concen-tration of salts and organics.
In this dying mill in Tirupur, the wastewater is first treated with biological treatment (tertiary treatment) to reduce the amount of organics in the wastewater. This step is followed by quartz filtration. The process water is then passed through an ion exchange treatment stage, consisting of the organic scavenger to remove the organic substances followed by water softening with Lewatit® CNP 80 WS. Since sodium sulfate is added during the process, calcium must be removed to avoid the precipitation of calcium sulfate.
After the ion exchange sequence, 85 m3/h water is passed through a reverse osmosis (RO) system with Lewabrane® RO S400 HR to remove salts and other remaining organ-ics. While the feed contains total dissolved solids (TDS) of 11,000 mg/l the RO process reduces it to less than 100 mg/l. The RO system operates at a recovery rate of 80%. The RO brine with TDS of around 50,000 mg/l is further treated by NF (nanofiltration) membranes to recover the sulfate, while the sodium chloride, which passes through the NF membrane, is concentrated by a multiple-effect evaporator. The sodium chloride salts are finally dried in a solar pan and disposed of as solid waste. The concentrate of the NF process, which contains mainly sulfate, is reused in the dying process.
State-of-the-art pretreatment is key to achieving these long lifetimes of RO elements while treating difficult industrial wastewater. The scavenger reduces the COD to a level of 35 ppm, which reduces organic fouling and the bio growth potential of the stream. The following softening reduces the hardness to less than 10mg/l, which results in a lower scaling potential. Combined with the high rejection and durability of the Lewabrane® S400 HR elements the expected performance and lifetime can be achieved.
The described industrial example shows that the reduction of wastewater, even in challenging process industries, is possible using the right tools. Lewatit® ion exchange resins and Lewabrane® reverse osmosis elements are a smart and efficient combination to treat wastewater that contains a high load of organics and high salinity.
In industrial water treatment applications, where a high load of organics could pass through pretreatment by ultrafiltration, the use of scavenger resins before RO treatment should be considered. The removal of organics will lead to decrease of fouling on the RO membrane.
Lewabrane® B400 FR elements are installed in the new BWRO plant of Egyptian fertilizer producer AlexFert in Alexandria, Egypt. The water treatment plant is fed with canal water (Nile river as origin) of seasonally variable TDS (300–550 mg/l). The water is pre-treated by coagulation, cold lime softening, and filtration. The RO plant consists of two trains, each of 120 m3/h feed stream and 74% recov-ery. A single train is composed of two stages in a 13:6 array with six elements per vessel. The RO units were placed into an existing water treatment plant, upstream of ion exchange full demineralization trains (SAC – WBA/SBA – MB, with Lewatit® MonoPlus resins).
From the beginning of their use, the Lewabrane® RO elements demonstrated their excellent salt rejection with up to 99.76 % (at 20 °C). This rejection leads to a permeate conductivity in the order of 3 to 5 μS/cm, which significantly reduces ionic load for the resins at the demineralization unit. While maintaining the demanded parameters of deminer-alized water, the cycle times of the demineralization trains are increased by up to four times (depending on season and with a possibility for further increase). Thus, the customer can reduce consumption of specific chemicals for resin bed regeneration by approx. 60%.
Lewabrane® B400 FR exhibits an excellent performance with the difficult Nile surface water. The measured rejection is above expectations. The combination of Lewabrane® B400 FR membranes and Lewatit® MonoPlus resins for demineralization leads not only to the requested final demineralized water conductivity below 0.08 μS/cm / 2 ppb SiO2, but also to a stable and reliable process. Further-more, the new RO plant allows a reduction of specific chemical consumption of the resin bed due to less frequent regenerations.