BLOG ACTION DAY 2010: WATER
THE WASTE WATER treatment works at Saltend certainly makes its presence felt on occasions via bad odours (which Yorkshire Water have pledged to tackle) – but what actually happens there? This is the question put to Yorkshire Water (YW) who provided a fascinating insight ‘behind-the-scenes’.
On average people in Yorkshire use about 150 litres of water a day through washing, cleansing, drinking and toilet flushes. 95% of this water returns to YW via our toilets, washing machines and sinks. 20,000 miles of sewers takes this, and drained surface water, to 0ne of 631 waste water treatment works (WWTW) across the region.
Large objects are removed first at the WWTW . Metal bars trap larger objects brought via the sewers such as nappies, rags, paper and other toilet debris.
Grit is removed next using air bubbles and gravity which forces the heavier material to the bottom where it can be removed. The waste sewage then travels into settlement tanks where remaining solids sink to form a ‘sludge’ – surplus water is pressed out and the concentrated sludge is sent off for disposal by incineration.
The liquid sewage passes into filtration tanks which involves biological treatment. Filters of stone containing billions of bacteria and micro-organisms remove any organic pollutants.
The sewage then enters the final settlement tanks where solids and organisms sink to the bottom. Harmful substances are removed at this stage. The remaining solids are pressed to remove water then are sent off for further treatment or to be made into compost. From here, the treated water can be returned to the environment.
The full story of what happens at a WWTW can be found at the YW website’s virtual tour.