Tillskottsvatten i Haninge kommun : Kan mängden tillskottsvatten kvantifieras utifrån uppfyllnadstid i pumpstationer?

The definition of additional water is as all water except wastewater contained in wastewater pipes. In heavy rainfall, the volume of additional water in the sewage water pipes become large and can cause several problems, including overflows and basement flooding. Many municipalities have problems with additional water. In a survey, 80 % of the questioned municipalities claimed that they actively work to reduce the amount of additional water in sewage water pipes. In Haninge municipality, additional water causes several basements floods each year and Fors treatment plant receives considerably more water than necessary. The high proportion of additional water at the treatment plant requires a high dose of chemicals, which is both expensive as well as time-consuming. Haninge municipality has a growing population and Fors treatment plant does not have the capacity to receive larger volumes of water, which could cause problems when new residences are to be built. Flow meters are usually used to quantify the amount of additional water, but flow measurement is expensive and requires planning. In Haninge municipality there are about 50 pumping stations and the purpose of this study was to determine whether the amount of additional water could be quantified based on the filling time in the pumping stations. A flow meter was used to obtain a reference value. However, at the pumping stations the filling times were not logged properly and could not be used in this study. Instead, the pumping times were used to quantify the amount of additional water. To calculate this, several parameters as volume of pump sump, pump running times, the flow when the pumps were draining and the amount of drinking water bought were required. To obtain a relationship, the volume of additional water for a wet compared to a dry year was used. A relationship between volume and running time could be distinguished, but since the flow measurement never worked, the values for the volume were uncertain. However, the relationship could be used to identify which areas that have a high proportion of additional water, but the quantification of the amount was uncertain. The relationship was then used to quantify the additional water for several different pumping stations. None of the investigated areas had any problem with additional water, but the areas around Hagtornsvägen, Vendelsögårdsvägs, Ålstavägens and Österhaningevägens pump stations have some additional water. In Haninge municipality there are some old areas that would had been interesting to include in this study, but there were no pumping stations there. In the future flow measurement will be important for Haninge municipality to further work on quantifying additional water and identifying problem areas. The flow measurement is not specific to pumping stations but can be placed on the sewage pipes at hubs to be able to distinguish which areas have the largest volume of additional water. However, looking at the running times gives a glimpse of where the problems are greatest and may also work as an indication of where on the pipelines the flow meters could be placed