Employees, such as those in the maintenance department, attempt to address this issue with varying degrees of success through various measures and equipment installations. Contamination of the cooling water by bacteria, viruses, algae, and fungi is typically managed by dosing chemicals, usually by adding biocides. Apart from the difficulties in handling these chemicals, the purchase of such substances, the necessary safety measures, and the personnel required for handling them result in significant costs. However, sustainable success is rarely achieved. Furthermore, the problem of contamination by solid particles persists, ranging from coarse particles that settle quickly to fine particles that disperse.
How can this problem be addressed without stringing together complicated individual processes or letting chemical use get completely out of hand? With ONI’s newly developed “AquaClean” system technology, a completely new system approach and, ultimately, an efficient solution have been found. Summarized in a profile, the technology is described as a systemically structured combination of devices. Measurement channels for conductivity, pH, redox potential, and flow rate, in conjunction with a high-performance computer, provide the information necessary for step-by-step cooling water treatment. The actual water treatment then takes place via various filter units as well as a downstream, intrinsically safe ozone reactor. A pump unit supplies the “AquaClean” system with a defined volume of water independently of the cooling water network, and the integrated lifting system ensures the discharge of backwash water—even in basement areas that do not have their own wastewater discharge point.
Multi-stage filtration
The basis for the highest possible water quality is the lowest possible concentration of solid particles and a low load of biological matter of various types. This is due to the different mechanisms of action of these substances, such as corrosion in the form of pitting or the obstruction of heat transfer by biofilms enriched with solid particles.
To achieve the best possible results here, the “AquaClean” system has been equipped with a multi-stage filtration system. The combination of several filter units, consisting of a backwashable AFM filter and a downstream, also backwashable ultra-fine filter with a filtration capacity down to 0.02 μm, ensures a massive reduction in solid particles as well as bacteria and viruses. This deprives the biofilm present in the system of a key source of survival and removes harmful biological contaminants from the flowing cooling water. To ensure as consistent a flow rate as possible to the filter units and to bridge the pressure difference between the piping system and downstream components, a pump unit has been integrated. This makes the system completely independent of the central cooling water supply and does not draw on any additional head reserves from it.
To combat biological contamination of the entire system, an intrinsically safe ozonation system is used, which is installed downstream of the filtration system. The highly reactive ozone not only combats biological contaminants in a very short time but also simultaneously oxidizes dissolved metals. The resulting oxidation products are then removed from the water via ultrafiltration. This effect significantly reduces the corrosiveness of the cooling water, allowing for a corresponding reduction in the use of corrosion inhibitors. Practical experience shows that after three to four weeks of system operation—even in extensive network structures—the bacterial load is reduced by up to 99.9 percent. All other biological contaminants are reduced to nearly the same extent.
