Annika Malm

Replacement predictions for drinking water networks through historical data.

Lifetime distribution functions and current network age data can be combined to provide an assessment of the future replacement needs for drinking water distribution networks. Reliable lifetime predictions are limited by a lack of understanding of deterioration processes for different pipe materials under varied conditions. An alternative approach is the use of real historical data for replacement over an extended time series. In this paper, future replacement needs are predicted through historical data representing more than one hundred years of drinking water pipe replacement in Gothenburg, Sweden. The verified data fits well with commonly used lifetime distribution curves. Predictions for the future are discussed in the context of path dependence theory.

The association of drinking water treatment and distribution network disturbances with Health Call Centre contacts for gastrointestinal illness symptoms.

There are relatively few studies on the association between disturbances in drinking water services and symptoms of gastrointestinal (GI) illness. Health Call Centres data concerning GI illness may be a useful source of information. This study investigates if there is an increased frequency of contacts with the Health Call Centre (HCC) concerning gastrointestinal symptoms at times when there is a risk of impaired water quality due to disturbances at water works or the distribution network. The study was conducted in Gothenburg, a Swedish city with 0.5 million inhabitants with a surface water source of drinking water and two water works. All HCC contacts due to GI symptoms (diarrhoea, vomiting or abdominal pain) were recorded for a three-year period, including also sex, age, and geocoded location of residence. The number of contacts with the HCC in the affected geographical areas were recorded during eight periods of disturbances in the water works (e.g. short stops of chlorine dosing), six periods of large disturbances in the distribution network (e.g. pumping station failure or pipe breaks with major consequences), and 818 pipe break and leak repairs over a three-year period. For each period of disturbance the observed number of calls was compared with the number of calls during a control period without disturbances in the same geographical area. In total about 55, 000 calls to the HCC due to GI symptoms were recorded over the three-year period, 35 per 1000 inhabitants and year, but much higher (>200) for children <3 yrs of age. There was no statistically significant increase in calls due to GI illness during or after disturbances at the water works or in the distribution network. Our results indicate that GI symptoms due to disturbances in water works or the distribution network are rare. The number of serious failures was, however limited, and further studies are needed to be able to assess the risk of GI illness in such cases. The technique of using geocoded HCC data together with geocoded records of disturbances in the drinking water network was feasible.

Cost-Benefit Analysis and Uncertainty Analysis of Water Loss Reduction Measures: Case Study of the Gothenburg Drinking Water Distribution System

Methods for controlling leakage from water distribution systems vary with respect to cost and personnel requirements. The benefits of leakage reduction should be compared to the cost of alternative management options to determine which is the most cost effective. This study presents a new method for evaluating leakage from water distribution systems via combined cost benefit analysis (CBA) and uncertainty analysis. The case study considers four alternatives for leakage control. The results show that the inclusion of uncertainty analysis represents an improvement over traditional CBA where there is a high degree of uncertainty in the input data. Moreover, a clearer understanding of the available alternatives is obtained in situations where multiple alternatives show similar performances and there is no clear best choice. It was determined that in the case study distribution system, it is significantly more cost-effective to reduce leakage volumes by reactively repair broken pipes than to proactively replace them, despite large leakage losses.

Hydraulic and hydrological simulations of the sewer system in the Majorna area, Gothenburg

As long as cities and urban life have been developed during the centuries, the conveying of wastewater and sewage have been important issues for municipalities and other authorities. The goal of municipalities is to convey, treat and reuse the wastewater in a way that does not harm public health and the environment. In the year 2010, Gothenburg Water utility decided to study and improve the sewer network system of the Majorna region, with a total area of 130 hectares, located in Gothenburg city. Hydraulic and hydrological properties of the sewer system were measured, modelled and simulated. Most of the input data needed for simulation was provided by the Gothenburg Water utility databases and a GIS-based map of Gothenburg sewer systems. The site measurements were taken between October and December 2010 and at two manholes where the measuring devices have been installed. The calibration of the model has shown that although there is a good correlation between the model results and the measured values at one of the measuring nodes at the area, there is a difference in the other one; the reason for which should be studied and investigated in another study. Finally, the tests and comparisons between the sewer system in this area and the standard values have shown that pipe leakages are the most problematic matter of the system and solving this problem will improve the system considerably.