Water and Effluent Treatment Magazine
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JANUARY 2018 WET NEWS 21 Enhancing effluent quality I n July 2010, Northumbrian Water decided to invest £5M in upgrading its assets and systems at Consett Sewage Treatment Works in the North- east. A swelling population within the plant's catchment area due to extensive residential development meant that demand for the treatment of wastewater would inevitably increase beyond the existing volume of 10Ml daily. As a result, the company needed efficient and robust technologies to ensure that there was no drop-off in the quality of effluent, whilst also meeting new and demanding consent levels with respect to suspended solids, phosphate ammonia and organics removal. Prior to work starting at Consett, the average flow was 14,342m3/day with the new plant designed to achieve a final effluent consent of 15mg/l BOD, 20mg/l TSS and 5mg/l ammonia. Phosphate levels De Nora Water Technologies was contracted by specialist contractor Carillion to design, manufacture, deliver to site, offload, install, commission and optimise five of its TETRA NSAF cells and four TETRA DeepBed filtration cells. The new processes would operate in series on a small area of des- ignated free land to ensure that the quality of effluent was maintained to the highest standards despite the increase deprive the river of its life source, oxygen. The investment by North- umbrian Water has signifi- cantly reduced the variability in the quality of the effluent, so the levels discharged to the environment are not impacted by seasonality, weather or other aspects which had caused problems in the past. The installation of NSAF and TETRA DeepBed Filters at this strategic sewage treatment works has also provided addi- tional capacity to support the economic regeneration of this important area of the North- east, and ensures compliance with European legislation and local environmental action plans. Positive Since completion of the works, Northumbrian Water has con- tinued to invest to improve the quality of water courses in the region and has achieved 100% delivery of its AMP National Environment Programme, according to data contained within the Environment Agen- cy's report on water compa- nies' performance in 2016. Stuart Barnes, treatment works manager (wastewater) at Northumbrian Water, believes the NSAF and TETRA DeepBed Filters have played a key role in achieving such pos- itive results. "Both NSAF and DBF work very well and pro- duce high quality final efflu- ent. Consett was built to accommodate growth in the Northumbrian needed efficient and robust technologies to ensure that there was no drop-off in the quality of effluent The NSAF is an upflow, fixed-film biological reactor Reductions in phosphates levels in the water have tackled potentially harmful and toxic algal growths THE CONCEPT • The De Nora TETRA NSAF is an upflow, fixed-film biological reactor generating minimal solids • TETRA DeepBed Filters provide solids and related phosphorous removal to meet stringent limits below 0.2 parts per million • Installation of the processes has delivered a 6% reduction the amount of suspended solids and almost a 15% reduction for phosphate NEED TO KNOW 1 The investment by Northumbrian Water has significantly reduced the variability in the quality of the effluent 2 The new processes have provided additional capacity to support the economic regeneration of this important area of the North-east 3 Since completion of the works, Northumbrian Water has continued to invest to improve the quality of water courses in the region in demand. At the same time, a reduction in phosphate levels would deliver further environ- mental and amenity improvements. TETRA NSAF is an upflow, fixed-film biological reactor that generates minimal solids requiring handling and dis- posal following treatment. The technology is robust and adaptable and can be engi- neered in a range of sizes – from small modular units suit- able for above or below ground construction to bespoke con- figurations for large plants. TETRA DeepBed Filters pro- vide solids and related phos- phorous removal to meet strin- gent limits below 0.2 parts per million. The system is a down- flow sand filter with a high loading capacity, making it ideal for handling peak loads. Installation of the TETRA NSAF and TETRA DeepBed Fil- ters has delivered a reduction of 6% in the amount of sus- pended solids and almost a 15% reduction for phosphate, improving the quality of efflu- ent discharged to an area of truly outstanding natural beauty. This has had a significant positive impact on the overall health and amenity value of the river systems as there are fewer solids to block out light and potentially increase silt in the river systems. Also, reduc- tions in the levels of phos- phates in the water have tack- led potentially harmful and toxic algal growths, that THE VERDICT "Before the plant was commissioned, if we had one or two of the eight filters standing, the effluent quality deteriorated to a point where the consent was at risk. This does not happen now" Stuart Barnes, Northumbrian Water • To support the economic regeneration of the Consett area and ensure compliance to meet demanding consent levels, Northumbrian Water needed to ensure effluent quality is maintained to the highest standards. INSIGHT Sewage treatment catchment, and a significant amount of this growth has now been realised with no impact on final effluent quality," he said. "We have seen an improve- ment in ammonia, biochemi- cal oxygen demand, chemical oxygen demand and solids removal. Before the plant was commissioned, if we had one or two of the eight filters standing, the effluent quality deteriorated to a point where the consent was at risk. This does not happen now." Barnes adds: "Phosphate removal has also improved, as a result of DBF solids removal, and has allowed us to reduce the ferric dose. Overall, the plant produces excellent qual- ity effluent, and it is relatively simple to operate."