Effect of manganese on biofilm formation

Manganese in drinking water

Manganese concentrations in the clean water at Brabant Water are generally lower than 1 µg/L. However, at some water production companies, this concentration is gradually increasing to values of 5 µg/L. Although manganese concentrations remain below the standard of 10 µg/L, the number of complaints about discoloured water from consumers in the area is increasing. A pilot study also found more sediment in drinking water with elevated manganese concentrations. An effect was also seen here on biofilm formation in the pipes.

Brabant Water is therefore studying the effect of low concentrations of manganese on particle formation, composition and behaviour. In addition, the study will look at the effect of manganese on biofilm formation. That will include the effect of chlorine, which is used for disinfection in most countries. Here, the expectation is that the manganese will not be oxidised by the biofilm but by the chlorine.

Determination and monitoring of biofilm formation

To determine the role of low concentrations of manganese in drinking water on biofilm formation in the distribution system, the extent of formation is being quantified experimentally using biofilm monitors.

Two biofilm monitors will be installed in a parallel set-up (pilot A and pilot B) supplied with clean water from the Welschap water production company (Figure 1). The supply to pilot A will contain manganese and/or chlorine, which will not be the case in pilot B (reference/control).

Biofilm formation will be monitored for 98 days using two traditional biofilm monitors with glass rings in pilot A and pilot B. ATP (the level of microbial activity), manganese and iron in the biofilm will be determined every two weeks. The same measurements will be made in the drinking water every month. The rate of biofilm formation will also be monitored.

Effective biofilm monitoring in drinking water systems

This study will:

• clarify whether low manganese concentrations in drinking water result in more biofilm formation in the distribution system;
• describe the effect of chlorine on a possible increase in biofilm formation in drinking water with low manganese concentrations;
• describe the level of complexation of other heavy metals with manganese in the biofilm;
• clarify the extent to which it is necessary to optimise existing treatment plants in order to remove manganese;
• further optimise the pilot set-up developed by Brabant Water, including a biofilm monitor as a new standard for easily studying the behaviour of particles and biofilm formation in a distribution network under controlled conditions.

Overview of the project set-up for testing the role of manganese. Chlorine was being passed through the system when the photo was taken.