System solutions for Water treatment plants Berlin

Which water treatment technology for which water quality?

Water treatment plants process different types of natural water sources (groundwater, surface water, …), dirty water and produce different water qualities according to the demand or optimized. Either they purify the natural raw water, which consists of groundwater, surface water or precipitation water. Or they clean private or industrial wastewater or process water.

Water treatment systems remove dirt and pollutants. As a means to an end, they supplement disinfection using chlorine, for example, or set the desired values via measurement and control technology. In most cases, water treatment operates according to a multi-stage system. More and more frequently, the systems are designed on an individualized basis. This is the case, for example, if a so-called micro-pollution by pharmaceutical substances exists or the composition of the output water requires this.

At the beginning there is often mechanical treatment by screens, filters or rakes. Parameter-specific measuring instruments are essential for the further treatment processes. They are missing in practically every water treatment plant.

An essential component of many purification processes is reverse osmosis. In reverse osmosis, water is pressed through a membrane to remove dissolved substances. This already achieves a high degree of purity, which is essential for many applications.

The technology used in the other water treatment stations varies depending on the end product and its hygienic requirements. In Germany, strict standards and laws apply to all types of water. However, they differ for process water, cooling water, drinking water or ultrapure water.

Ultrapure water places the highest demands on the water treatment plant

Drinking water is generally regarded as the most important resource. The top class of water treatment, however, is called ultrapure water. Here, the quality standards are the highest. Ultrapure water must be free of any foreign substances.

The reason: ultrapure water is needed in the pharmaceutical industry and medical technology, among others. A technical term used there is pharma water. Ultrapure water is also used for research purposes, semiconductor production and the production of food and beverages. The production of ultrapure water is technically extremely complex and requires the most precise measurement and control technology.

Strict water treatment specifications apply to drinking water

Drinking water is absolutely irreplaceable as food. Evolution has adapted humans to longer periods of hunger, but not to “dry spells”. A healthy person can survive up to two months without food, provided he has sufficient water. Without drinking water, however, he can only survive for about three to four days.

Modern wastewater treatment for a city like Berlin is inadequately described by the popular term sewage treatment plant. For the public water supply, the strictest specifications apply according to DIN standards 2000 and 2001. Similarly, standards regulate the planning, construction and operation of treatment plants for drinking water, which must be continuously monitored by regional utilities and compliance with which must be verifiably documented.

According to the Drinking Water Ordinance, the pH value of the water must be between 6.5 and 9.5. The ideal values are considered to be 6.5 to 7. Only chlorine gas, sodium and calcium hypochlorite, chlorine dioxide and ozone as well as UV rays may be used to disinfect the water. The most common method of disinfection is the addition of chlorine.

Chlorination offers the advantage that the risk of recontamination of the water is the lowest. However, its use depends on the pH value of the water. It can be corrected by adding chlorine-containing acids. The quantities required depend on the chlorine content of the water, the quantities purchased and the disinfection requirements.

Regulations for process water in water treatment plants

Process water is required in industrial plants or for the manufacture of products. Increased quality requirements apply. Parameters such as the electrical conductivity of the water, the TOC value, etc. often play an important role.

Further regulations for water treatment and measurement and control technology concern the solids content, the gas content, the water hardness and the pH value. The reason for this is that certain substances contained in water can damage technical equipment or impair its functionality.

Water treatment for industrial water and cooling water

Service water is also called process water or industrial water. It is not intended for consumption, but for technical, domestic or commercial use. Consequently, service water must also meet a certain minimum hygiene standard and be reliably cleaned of dirt and germs.

Cooling water plays an important role in industry and energy production. Water is the most commonly used means of cooling, but also for removing thermal energy, for example in power plants. A distinction is made between open cooling water circuits or once-through cooling systems.

In any case, microorganisms must be eliminated effectively. In particular, it is important to avoid the formation of biofilms and the proliferation of legionella. Biocides are used for this purpose. The EU Biocide Regulation and the German Ordinance on Hazardous Substances apply. Recooling plants operate according to the VDI guideline for the operation of cooling towers. The requirements for the operation of such plants have been tightened considerably in recent years, for example by Din 2047. In particular, the technical suitability of the operating personnel as well as the documentation obligation are more than ever in the focus of the supervisory authorities.

In many cases, water treatment plants use oxidizing biocides based on organic or inorganic chlorine compounds. However, the use of oxidative biocides must be monitored continuously and indefinitely. State-of-the-art measurement and control technology is essential for this. Biocide control variables and dosages are based on either amperometric or direct photometric measurement techniques. Both are generally used for direct measurement of the product content and thus the optimized use of chemical products.

The measurement of the redox potential can be used to measure the oxidation or reduction in water. However, the measurement results are only suitable as parameters for monitoring. Discontinuous measurements are made possible by the DPD method according to DIN EN ISO 7393-2. This measurement technique can be used to determine the amounts of total chlorine and free residual chlorine. DPD stands for N,N-diethyl-p-phenylenediamine. It reacts with water from pH values between 6 and 7 and leads to the formation of a red dye. From the intensity of the dye, conclusions can be drawn about the total chlorine content in the water. The difference between total chlorine and free chlorine finally gives the combined chlorine, which is essentially formed from chlorine amines.

The harmful ingredients accumulate in the water in proportion to the dye concentration present or the amount of free chlorine present.

The processes in modern water treatment plants are largely biological or chemical in nature. However, the basis of all decisions and measurements are precise measuring instruments and control devices.

State-of-the-art technology for water treatment from Neomeris in Hildesheim, Berlin.