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Title: Water conservation impact on solid transfer in sewers
Author: McDermott, Rodney Patrick Joseph
ISNI:       0000 0004 5370 3690
Awarding Body: Ulster University
Current Institution: Ulster University
Date of Award: 2014
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The scope of the study was to investigate the impact of water conservation on several aspects of solids transfer during low flows in sewerage systems which service small catchments. A newly constructed test-rig allowed for several test regimes in a small catchment, using simulated faeces. The test-rig encompassed WCs/bathrooms, lateral sewers, junctions, three branch sewer types, including a wide egg-shaped pipe and a main sewer which were all adjustable for height and gradient. Testing addressed gaps in the research including simulated human faeces, impact of wipes, cistern height adjustment, effects of non-invert level junctions, single occupancy dwellings, white goods discharge, bath and shower discharge patterns, degradation of human faeces and variable gradients. Original contributions are: 1. Simulated human faeces has been developed; this organic material is known as "The Buncrana". 2. Degradation of human faeces can take place in at least eight stages; this was also verified for the Buncrana. 3. Physical conditions can exist to provide unlimited solid transfer distance of given organic material, in contrast to work of previous researchers. 4. For a given solid and a 6.0 litre flush, limiting solid transfer distances (LSTD) can be established in a 30.0 m long 160 mm OD PVC pipe but not in the equivalent wide egg shaped sewer/pipe. The LSTD values are based on a single solid that is not combined with toilet paper or toilet wipes. 5. The wide egg-shaped pipe/sewer has advantages over circular pipes and at a 1/50 gradient can transfer the Buncrana a minimum of 30.0m with a maximum of 3 No. 6.0 litre flushes. For the same gradient and flush conditions the equivalent 160 mm OD PVC results in transferring the Buncrana circa 10.30511" However solid degradation was inhibited in the wide egg-shaped pipe. 6. Sewer pipeline configuration is key; a "minimum distance to convergence point" must be established to maximise use of water other than WC flush and prevent it bypass solids. 7. A methodology for the scoping of a code of practice for low flow testing has been drafted. 8. Risk of sewer blockages from single occupancy dwellings arises from adhesion of human faeces to the sewer. This thesis has recommended significant further research to provide innovation in the design of sewers to cater for water conservation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available