Highest water quality through continuous membrane monitoring

Water is the elixir of life for everyone and its quality must be protected, also in the future. In reverse osmosis and nanofiltration plants for drinking water treatment, high-performance filter membranes perform several important tasks at the same time, such as removing microorganisms, particles, salts and other substances. Therefore, safe monitoring of their correct operation is essential for high water quality and reliable service.

The Pforzheim public utilities use a scalable and flexible permeate monitoring system for their new reverse osmosis system in the Friedrichsberg waterworks, which requires almost no time at all to detect, document and report even the smallest leaks or membrane fractures. This not only guarantees clean drinking water at all times, but also saves the plant operator the time-consuming job of manual water sampling.

A trend report that provides information on the membrane integrity of the individual pressure pipes can be prepared for each pipe separately. This allows problems to be quickly located and rectified and unscheduled plant downtime to be avoided.

The reverse osmosis system in the Pforzheim waterworks

Reverse osmosis is a physical process for the concentration of substances dissolved in liquids, whereby pressure is used to reverse the natural osmosis process.

The reverse osmosis plant at the Pforzheim waterworks consists of two lines, each featuring 20 filter modules of 1 m in length where the wound membranes are located. With a yield of 80% permeate and 20% concentrate, almost 300 m³ of desalinated and purified water are produced per hour in order to always achieve the desired drinking water quality.

The decisive factor for filtration is that the wound membranes, connectors and seals do their job perfectly. If correct operation is adversely affected, it is important to react in good time, as unwanted substances may enter the drinking water in the event of a membrane rupture.

Time-consuming manual measurements of the permeate

Generally speaking, the conductivity is measured via a continuous online measurement in the permeate manifold. Since the “dilution” of leakage water due to the permeate is very high, defects are only detected at a very late stage. In addition, the pressure pipes are regularly checked through manual measurements, the values are entered into the computer system by hand and the state of the membranes is subsequently assessed. This demands a considerable amount of effort from the plant operator on-site.

Permeate monitoring system: greater safety through early detection of membrane damage

On the recommendation of the Water Technology Centre (TZW) in Karlsruhe, a competent contact point for all questions relating to water quality, drinking water quality and water technology, the Pforzheim public utility company opted to use a permeate monitoring system from Bürkert in the new drinking water treatment plant.

Instead of the usual measurement in the permeate manifold, this monitoring solution now monitors correct functioning of each individual filter module fully automatically and detects even the smallest of leaks that were previously not detected at all or only detected at a very late stage. The complete system provides the entire hardware and software required for this purpose.

The investment has paid off, as the system saves costs in the short, medium and long term due to higher plant availability and reduced inspection and maintenance expenditure.

Permanent plant monitoring for predictive condition assessment

The permeate monitoring system automatically removes the sample water from the 40 pressure pipes of the reverse osmosis plant, one after the other, and carries out a water analysis. When one pressure pipe is being inspected, the next sample water line to be measured is rinsed. This helps to avoid dead times, while sample water consumption is reduced to a minimum and almost permanent monitoring of the drinking water quality is ensured. The system measures various parameters, including conductivity, turbidity, pH value and chlorine content, and triggers a warning if the set limit values are exceeded. Since all measurement data is recorded, membrane ruptures can also be detected at an early stage using a trend analysis.

Easy installation and integration into the higher-level control

Installation of the online analysis system was very fast thanks to pre-assembled control cabinets and defined interfaces. All common interfaces are available for integration into the plant-specific communication system. In Pforzheim, the permeate monitoring system communicates via a Profinet interface with the higher-level control system of the drinking water treatment plant. This means the responsible employees always have an overview of the state of the filter modules.

The permeate monitoring system is based on the valve island Type 8640; it is therefore highly scalable and suitable for small to large plants in which, for example, up to 200 pressure pipes are monitored in one control cabinet.

Preventive maintenance reduces operating costs

In the meantime, the solution has proven successful in practical applications. The waterworks employees were convinced by the possibility to respond more quickly to any functional restrictions of the filter membranes. Manual sampling and entries into the computer system can now be dispensed with fully. The new permeate monitoring system also completely eliminates the need for lengthy troubleshooting in the event of a leak.

Modular valve island for pneumatics

Type 8640

• Compact design
• Modular configuration
• Higher flexibility in control cabinet due to AirLINE Quick
• Simple exchange of valves (with option “P-shut-off” – also possible during operation)

Would you like to discover more about the permanent membrane monitoring or the permeate monitoring system from Bürkert? Contact us now: