Specialised return liquor treatment at Whitlingham – UK’s first full scale example of the SHARON process
Riches, S.1 and Nossiter, P.2, 1Anglian Water, 2Black & Veatch, UK
(free)
Abstract:
The increasing use of enhanced digestion of biosolids has led to an increasing demand for treatment solutions of high strength nitrogen and phosphorus rich return liquors arising from enhanced digestion. Sustainable, capital and energy efficient treatment solutions for these liquors are an important part of successful implementation of enhanced digestion processes. This paper outlines the selection, start-up, commissioning and optimization of a SHARON (Stable High Ammonia Removal Over Nitrite) Liquor Treatment Plant (LTP) at Whitlingham Sludge Treatment Centre (STC) where a CAMBI thermal hydrolysis enhanced digestion stream has recently been installed.
Key words
Liquor treatment, Enhanced digestion, Thermal hydrolysis, Commissioning, Plant optimization
Introduction
Anglian Water provides water and wastewater services to approximately 6 million customers. In 2009, Anglian Water produced 184 thousand tonnes dry solids (ttDS) of raw sewage sludge for treatment and has installed capacity to treat approximately 100 ttDS/annum of this sludge by enhanced digestion. The SHARON LTP forms part of Anglian Water’s biosolids capital works programme at their Whitlingham (Norwich) Sludge Treatment Centre (STC). The overall biosolids project at Whitlingham comprises the upgrading of the existing biosolids treatment plant to provide treatment capacity for approximately 21 ttDS/annum. This approximately doubles the capacity of the plant allowing treatment of biosolids imported from surrounding smaller sewage treatment plants, previously treated by lime stabilization, to be enhanced digested by a thermal hydrolysis CAMBI plant followed by mesophillic digestion in 2 anaerobic digesters. The plant is designed to achieve the Agricultural Development Advisory Service (ADAS) Enhanced Treatment Standard. A consequence of increasing the quantity of biosolids treated by enhanced digestion is that the associated liquor flow and loads also increase to the detriment of the works discharge consent standards. This led to the installation a new Liquor Treatment Plant (LTP), to reduce the aqueous ammonia and phosphorus concentrations contained in the liquors.
Whitlingham STC generates return liquors from three sources 1) surpus activated sludge (SAS) thickening liquors, 2) pre-digestion liquors, and 3) post digestion liquors. In order to maximise the available capacity of the existing effluent treatment facility and minimise the size of any LTP the SAS thickening liquors and pre-digestion dewatering liquors were returned to the existing wastewater Enhanced Bio-P removal (EBPR) plant for treatment. The much stronger post-digestion dewatering liquors were treated in a new dedicated LTP with the effluent from the LTP being returned to the EBPR plant for further treatment. A process block schematic is shown in Figure 1.
