Water & Wastewater Treatment

WWT April 2017

Water & Wastewater Treatment Magazine

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Page 37 of 51

T he aim of any sewerage system is to collect wastewater from residential, industrial, and ser- vice establishments and to transport it to a works for its treatment and safe disposal. Environmental and eco- nomic considerations dictate that this should be achieved without blockages, which require troublesome manual intervention, and with the optimal use of energy. Pumping stations are a natu- ral focus for attention in sewerage systems, since not only are they the site of many blockages, but the energy used by the pumps is the major cost involved in handling wastewater. However, while the energy e• ciency of wastewater pumps has risen up the agenda in the last two decades, reli- ability is always the primary concern. This is because pumps that become easily clogged by sewage solids are ultimately ine• cient, no matter how energy-e• cient they may be when they are running smoothly. Yet wastewater pumps do not oper- ate in isolation. The e• ective handling of wastewater requires not only good pumping equipment, but a wet well and surrounding sewer system that has been designed to give the pumps the best chance to deal with whatever the nature of the e• uent that comes their way. The purpose of this CPD article is to explore some of the factors that are most important in the design of pump- ing stations - and pump sumps in particular - and to explain how better design can help the pumps to operate e• ectively without clogging. Solids characteristics In order to understand the challenge pumping stations face, it's necessary to consider the di• erent types of solids present in raw sewage. These include not only faecal and organic matter, in the form of gross solids or sludge, but other items ƒ ushed into sewers by users such as paper, rags and sanitary waste. Because of the combined nature of the sewer network in the UK, our sew- ers also contain other types of solids which have entered the system with stormwater. This includes silt, sand, and gravel that has been washed or blown from unpaved areas, road sand, and grit from deicing operations or from the abrasion of roads, material from construction work, and litter such as paper, plastics and drinks cans. Typically, in industrialised coun- In the know CPD article Pumping station design SPONSORED BY Optimal pump sumps for wastewater In this CPD article, we look at how pumping stations can be best designed to deal effi ciently with solids and sediment in the wastewater network 38 | APRIL 2017 | WWT | www.wwtonline.co.uk The Optimal Pumping Station (TOPS) was designed by Flygt as a self-cleansing sump

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