Municipality of Kungalv




Surface water


The municipality of Kungälv needed a wa­ter treatment plant that is very effective in dealing with Natural Organic Matter (NOM). It also required a robust produc­tion capacity that is easily upgradable. The process devised for the new Kungälv water plant was tested for a full year to see if it would be up to the task in different conditions. The pilot trials were executed by Purac, a leading Scandina­vian contractor in water and wastewater treatment.
As the ultrafiltration system is the heart of the overall drinking water treatment plant, Purac has worked together closely with Pentair X-Flow, who delivered the UF pilot unit and full-scale UF units, as well as engineering support.

building a state-of-the-art drinking water plant

The town of Kungälv in Sweden decided to build new treatment facilities for producing drinking water. In a process of close cooperation, the Küngalv municipality, process partners including Purac,

and Pentair engineers went through every step from development to operational excellence for building state-of-the-art facilities that will eventually also supply drinking water to neighboring communities.


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.
Higher average temperatures will bring much more pre­cipitation that will have a marked effect on the quality of raw water sources for drinking water. Excess surface runoff brings high humus levels and algal blooms fed by nutrients from fertilizers, entering the aquatic system and causing excessive growth. Microbial contamina­tion will increase in raw water sources as a result. The existing drinking water treatment process in Kungälv was strug­gling to meet the required microbiolog­ical barrier levels, as several wells were being increasingly affected.

process in four steps

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.
The in-line coagulation is controlled by feed forward control. 
In the third step, the water is treated with activated carbon filters in order to remove the last traces of chemical substances, odor, and taste. In the fourth and final step, the water is alkalized with sodium carbonate and carbon dioxide. Before distribution, the water is also UV-treated to provide a second and independent microbiological barrier.

ultrafiltration system

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. 
Membrane+ is the X-Flow approach to ensuring success in every filtration project through close involvement and cooperation from the first concept to full-scale operations. Expert assistance, especially from an early stage onward, will always make the difference in terms of quality, safety, efficiency and reliability. The Pentair X-Flow engineers are committed to provide all practical support you need in every one of the four main project phases.

Membrane plus approach

Pentair X-Flow - Global Service

development phase

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.
The frequent interactions and meetings with the Purac engineering team helped me to understand and meet their specific requirements. Working together closely in every project phase enables us to deliver successful and sustainable ultrafiltration solutions.’

Kungalv drinking water plant

Execution phase

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 end client, specifically the team of Kungälv operators, was very enthusiastic about commissioning and operating their new drinking water plant. At that point, they had also become familiar with our UF technologies and project approach.’

Operation phase

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.
These spectroscopy methods use X-ray and infrared light re­spectively to identify organic, polymeric, and inorganic materials in test samples.

“We are very pleased with our new water treatment plant, especially the ultrafiltration process.”

- Andrew Holmes, Process Engineer Kungalv

Excellent performance

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.
Coagulant dosing combined with feed forward control actively reacts to changes in feed water quality. The system has already proven to react adequately to peaks in NOM, for example after a storm. It always operates with minimum dosages and thus contributes to maximum permeate quality.

Easy future expansion

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.
The plant will eventually also supply drinking water to the municipalities Ale, Stenungsund, and Tjörn. ‘We are very pleased with our new water treatment plant, especially the ultrafiltration process’, says Kungälv Process Engineer Andrew Holmes. ‘The water after the UF stage and in our distribution system is of superior quality, both chemically and microbiologically. We has been very pleased with how Pentair have responded and worked with us to resolve any issues that arose during commissioning and the first year of operation. We have signed a service contract with Pentair. We hope it will ensure that we always have up-to-date knowledge of the membranes’ performance and condition, which in turn will help secure long membrane life.’

Process scheme

Technology Xiga Aquaflex
 Membrane surface area 57 m2 57 m2
Installed membrane elements +open positions unit 240+120* 32 + 28*