Expertise reports from Dr. Nähring Water Treatment GmbH
An expertise is a report written by experts on a specific issue in a particular field. As experts in the field of antiscalants and purifiers for membrane plants, we provide expert reports in the following areas:
- Expertise after evaluation of plant data for problem identification
- Expertise as part of a membrane autopsy
- Expertise as a plant audit: reduce operating costs by optimizing pre-treatment, operation, use of antiscalants, membrane cleaners and other chemicals used
- Expertise through laboratory studies on fouling and scaling and their control
Expertise membrane blocking by barium sulfate
Barium sulfate (BaSO4) is the barium salt of sulfuric acid. In nature, barium sulfate occurs in the mineral barite, which serves as the main raw material for the production of other barium compounds. In some algae, such as the cells of Closterium, barium sulfate occurs in the normal orthorhombic baryte form. In the ciliate Loxodes, it has been demonstrated that the barium sulfate crystals serve as gravity receptors due to their high density. Barium sulfate is a white powder that is virtually insoluble in water, acids, and alkaline solutions, while it can be dissolved up to 12% in hot concentrated sulfuric acid. At high temperatures (> 1400 °C), barium sulfate decomposes to barium oxide, sulfur dioxide and oxygen. Due to its poor solubility, the mineral is not a hazardous substance, unlike all other barium compounds.
In the case of one customer, the problem was a membrane blockage in an ultrafiltration plant. During the first two years of operation of an ultrafiltration plant for the treatment of drinking water, a membrane coating of barium sulfate had formed despite regular backwashing, which greatly reduced the permeability of the membranes to only 25 L/m² × h × bar.
A high sulfate content in the raw water combined with the presence of barium can lead to the formation of barium sufate in the ultrafiltration membranes in case of a corresponding oversaturation. Within the scope of the expertise, intensive investigations on the membranes have shown that the residues are mainly barium sulfate, in smaller quantities also strontium sulfate. A cleaning with the alkaline membrane cleaners Memobrane 35 and Activator completely removed the barium sulfate residue. The permeability of the membranes after use of the membrane cleaners had reached> 500 L/m² × h × bar.
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