Kungalv

The municipality of Kungälv in western Sweden near the city of Gothenburg was facing two main challenges concern­ing its drinking water supply. First, a fast-growing number of households is increasing local and regional demand for drinking water, while at the same time the existing ground infiltration plant was at maximum capacity and could not be expanded. Second, the design of a new treatment plant to take water directly from a river susceptible to varying water quality conditions. The treatment plant is located near Kungälv on the bank of Sweden’s largest river: the Göta river. The COD levels in this surface water are on the rise, and climate change is only going to push them higher. The river is also a strategic transport route and has several wastewater treatment plants that discharge into it.

The selected process scheme comprises four treatment steps to reduce or eliminate the risks posed by NOM, viruses, and pathogens. In the first treatment step, the river water is naturally aerated in an aeration cascade. The water passes through rapid gravity filters containing Filtralite®, a highly porous media filter that removes iron and turbidity and improves water quality and biostability. The second step is UF membrane filtration, in which bacteria, viruses, and parasites are removed. Furthermore, in combination with coagulants, the membranes will remove more than 50 percent of NOM, measured by UV254.

To increase the overall system water recovery and to reduce the waste stream, there are two successive ultrafiltration stages. The primary UF system uses the Pentair X-Flow Xiga Solution, the highest surface area-to-footprint ratio in the market, and its backwash waste is treated with the secondary UF system that uses the Pentair X-Flow Aquaflex Solution, the proven technology for high solids membrane filtration applications. 

Pentair Pilot Engineer Martijn Lesscher was involved in the development phase, working together with Purac on the piloting. ‘The combined effort of all operators has made this trial a success. performance.’ During the design phase, various calculations were made for the complete UF system, including all equipment specifications and selection guidelines for a robust system design that meets best engineering practices for operational efficiency and reliability. ‘Our process design and calculations also covered the neutralization system, and the tank dimensioning for the UF system.

Among other things in this project, Pentair Process Engineer Jasper König was responsible for commissioning and training in the execution phase. ‘I was involved in the engineering and commissioning of the project. We worked together well with the Purac engineers.

The membrane performance is contin­uously evaluated based on historical trends, and settings are optimized wherever possible to further increase the plant’s effectivity, extend membrane lifetime, and lower operational costs. A service plan covers frequent check­ing of the membrane condition with a Memscan that provides relevant information about the remaining lifetime and potential fouling issues through EDX and FTIR analysis.

The new plant has been delivering drinking water to the town of Kungälv since December 2018 and is showing excellent performance. The use of UF membranes in combination with coagulants results in the removal of NOM and microbiology in a single process step. With the automated integrity test, the client can check the integrity of the system. The biological filter improves the water quality and improves membrane performance in terms of process stability and coagulant usage.

The close cooperation and exchange between all involved in the project have resulted in a world-class drinking water plant. Currently running at 7,500 m3/day, performance is meeting all expectations. During a two-week performance test, the plant was operated at its maximum capacity of 17,200 m3/day. Any future upgrade with a view to also supply neighboring communities is expected to be realized without any issues. The Kungälv treatment plant has attracted lots of attention and visitors during the first year of operations. It has fired the local imagination with its ability to take water from the Göta River and produce 200 liters of crystal-clear drinking water every second.