2H Water Technologies Helps Yorkshire Water Reduce
Ammonia and Cut Costs at Wetherby STW
Yorkshire Water’s Wetherby STW provides waste water treatment services for the 23,000 residents living in
the market town of Wetherby and its surrounding, predomninatly rural, area. During its operational
lifetime, the Wetherby STW has been developed, refurbished and generally enlarged to service the changing
needs of an increasing local population.
In 2015, Amey Black & Veatch (aBV) were engaged by Yorkshire Water (YW) to investigate, design, construct
and commission a tertiary nitrifying trickling filter (TNTF) system. As part of the project, 2H Water
Technologies was commissioned by aBV to design, manufacture and install the TNTF’s structured plastic
media and rotary distributor.
Cutting Costs, Improving Performance
The design and assessment process continued over a period of 18 months. The original plan was to build
two off filters which would handle the full works flow but that, and a subsequent proposal which entailed
two filters handling 50 per cent of the flow, was rejected for budgetary reasons. At that point, 2H
presented a third option which involved a single filter handing 50 per cent of the flow to
full treatment (64l/s). Not only did this option meet Yorkshire Water’s financial requirements but also provided
the reassurance of a performance guarantee based on our process design parameters and, importantly, met
Yorkshire Water’s asset standards.
Our performance guarantee is based on an agreed set of incoming flow design parameters. The feed BOD, COD
and suspended solids loads to the TNTF were based on the 95 per centile values obtained from a 9-day
sampling programme undertaken in November 2014.
Designed and Delivered
Work commenced at the site in July 2015. Deadlines for the project were tight because Yorkshire Water
wanted the TNTF to be operational by early November to allow time for the system to be biologically seeded.
In addition to designing a BIOdek structured plastic media solution for the new TNTF, 2H worked closely
with the main contractor on many aspects of the project. For example, 2H defined the operational
characteristics for the distributor wetting rate and the flushing intensity and collaborated with aBV on the
electrical aspects of the distributor’s motor drive system.
We mapped out the requirements for the filter base and the dwarf walls on which the media supports are
located. In addition, we supervised the site work for the BIOdek trickling filter solution plus all
operational and safety aspects associated with the installation. On completion of the project, 2H oversaw
wetting rates and flushing tests and provided a comprehensive O&M package.
The new BIOdek plastic media TNTF was installed – and still sits – between the final settlement tank
outlet and the tertiary mineral filter inlet. The BIOdek media and distributor are enclosed in an epoxy
coated steel tank complete with a closeable ventilation system. Within the tank, the media is supported on
reinforced concrete beams 140mm deep x 100mm wide on 400mm centres.
BIOdek TNTF Goes Live On-Time and Within Budget
The BIOdek TNTF went into operation on the pre-agreed date of 6th November 2015 thanks to a high-quality,
well-managed installation project that met all the stipulated targets. As outlined in the contract, 50 per
cent of the plant flow is diverted into the BIOdek TNTF wet well via a low-level splitter chamber. After
being treated in the TNTF, the flow is combined with remaining 50 per cent and directed to the existing mineral
To comply with the 2H performance guarantee, the distributor provides a fixed flow of 83l/s which ensures
controlled flow distribution – with better than 10 per cent variation across the media – and a similarly
controlled flushing system.
The go-live date was chosen to include a 63-day period during which it would achieve the agreed design
parameters before external sampling commenced in March 2016. Confirmation that this objective was achieved
came in January 2016 with the successful completion of a 14-day process reliability test.