Identification of measures to achive a more optimalized sewer network considering the challenge of I/I of non sewer water

It is assumed that Infiltration and Inflow of non sewer water (I/I- water) causes major challenges for many municipalities. I/I- water is ?clean? water, which finds its way into wastewater pipes. Sources of I/I- water may be drinking water, groundwater or storm water. I/I- water leads to a number of unwanted consequences: pumping of unnecessary quantities of water, overflow through weirs, possible pollution of waster in rivers, streams and sea and enlarged costs at waste water treatment plants. I/I- water finds its way into a poorly functioning wastewater system through damaged pipes and damaged manholes and fault connections, that is, coupling of storm water directly in to the wastewater system. The challenge regarding I/I- water varies. It is therefore of interest to investigate how big the problem is for different municipalities in both Norway and other European countries. It is also relevant to look into how the development has been in recent years. The first part of the project will investigate what the status of I/I- water is and how the share of I/I- water has developed for the past 10 years in Norwegian municipalities and other relevant European cities. In order to be able to work effectively trying to reduce I/I- water, it is essential to document which sources give the biggest contributions. I/I- water is in many sites under the influence of rainfall, but it is assumed that other sources of water also make a big contribution. To be able to differentiate sources, a multivariate analysis can be performed. Such analysis may help to find patterns and hidden contexts that are hard to discover if one only takes into account the impact different factors have on the I/I- level separately. In the second part of the project, it is planned to conduct multivariate analysis for various municipalities in Norway. The goal is to reveal connections between I/I- water and different influencers. The third part of the project will look into the consequences of I/I- water. The consequences will be investigated from an economic perspective. Whether it will be worthwhile to spend a lot of resources trying to solve the problem of I/I- water will depend on the extent of the consequences. A cost / benefit analysis will be performed on different measures that can solve existing challenges. This part of the project will emphasize developing a simple methodology to assess whether measures are economically profitable or not. I/I- water may be compared to leakages from the water supply system. Both are symptoms that the piping systems are leaky. Drinking water leaks from the water pipes and ?clean water? finds its way into wastewater pipes. ?Norsk Vann? has developed a methodology to find an "optimal" level for leaks from the water supply system. This optimal level may be found at the intersection between the benefit one can gain from measures being done, and the cost of the same measures. The methodology developed for the water supply system may probably to some extend be transferred to the wastewater systems and I/I- water. The subproject aims to find a methodology for finding the "optimal" I/I- level. Finally the project will try to investigate whether or not the measures that are being performed to prevent I/I- water are sufficient enough. What measurements are usually made before and after measures? And are existing methods to document effect good enough? A test area will be established in Asker municipality. The test area will consist of an extensive measuring program to help document the effect of various measures. In addition, measures inside the test area will be performed step-by-step so that one hopefully will be able to see which measures have the best effect. This last subproject will compile and test methodology that has been developed through the earlier phases of the project. The project as a total may be summed up as follows: 1. To investigate to what extend /I- water is a challenge to Asker municipality and other European cities, and how the development has been over the past 10 years 2. To investigate what factors that influence the share of I/I- water the most and develop a method to document these factors 3. To document the financial consequences of I/I- water in order to help making good decisions trying to prevent I/I- water 4. To find a methodology to document the effect from different measures and also to be able to differentiate measures regarding effect on I/I- water

Økt kunnskap om fremmenvanns påvirkning på avløpssystemet. Resultatene vil også være et godt grunnlag for videre forskning rundt temaet.

Tiltakene mot innlekking og utlekking kan være mange: tetting av ledningsnett, fjerning av feilkoblinger, nedleggelse av overløp, separering av spillvann/overvann, fjerning av bekkeløp som kommer inn på kloakksystemet, oppdimensjonering av ledningsnett og installasjoner. Metodene for å dokumentere effektene av tiltakene kan være å måle vannføring, kalibrere inn avløpsmodeller, måle overløpsdrift og måle vannkvalitet i resipienter. Oppgaven tar mål av seg å si noe om hvor store utfordringer innlekking/utlekking skaper for et utvalg av norske kommuner, hvilke tiltak som har størst kost- nytte- verdi og hvilke parametere som bør være styrende for hvor tiltakene skal settes inn. Dette vil gi en bedre ressursutnyttelse for kommunen.