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Bridging the gap between sewer status and new sewer inputs

Bridging the gap between sewer status and new sewer inputs A decision support tool to predict the effect of food waste disposers (FWDs) effluent on small-diameter sewers. Jonathan Mattsson, Annelie Hedström & Maria Viklander Department of Civil, Environmental and Natural resources engineering

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Bridging the gap between sewer status and new sewer inputs

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  1. Bridging the gap between sewer status and new sewer inputs A decision support tool to predict the effect of food waste disposers (FWDs) effluent on small-diameter sewers Jonathan Mattsson, Annelie Hedström & Maria Viklander Department of Civil, Environmental and Natural resources engineering Urban Water

  2. To develop an easy-to-use tool to identify pipes vulnerable to increased deposition by FWDs. To compare the developed tool to methods to assess self cleansing conditions (P90 and EN 752-2008) Objectives of present study Ordinary deposit FWD-deposit

  3. Two unfavorable pipe-settings out of these three reported to cause build-ups: Gentle inclination (%) Few households (i.e. low wastewater load) A large sag area (m2): Interdependent factors

  4. Pipes with at least two unfavorable settings  Class B Pipes with at most one unfavorable setting  Class A. A-pipes compared to B-pipes in terms of build-ups of deposits (students t-test, conf int. 95%). Will B-pipes exhibit more deposits? ”Two out of three”

  5. Method - Data used Three sewer systems serving single family housing were inspected using CCTV. FWDs were installed in ca 75% of hlds. Larger build-ups of finer sediments and finer sediments together with sanitary waste were documented for each pipe.

  6. Selection of settings, A or B? • Initial settings (based on literature values): Inclination: 0.9%; Sag area: 0.07 m2; No. Households: 8

  7. P-values from the outcome of the calibration: Result - Calibration Values in parenthesis are % of A-pipes

  8. Settings:Inclination: 1.0%, Sag area: 0.07 m2 N0 of households: 8 Applying the established settings

  9. The tool could be used for homogenous sewer networks. • Many pipes classified as ”B” • Improvements: Extreme values (e.g. negative inclination), manholes. • Cause for concern: Intermittent flow, deposits really stuck? Concluding remarks

  10. Thank you

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