Aerial view of primary settlement
tanksWith a population equivalent of 400 000, Esholt WwTW
was one of Yorkshire Water’s largest works that required
improvements to the quality of the discharge in order to meet the
Freshwater Fish Directive (FFD). As part of these improvements, the
works has undergone a major rebuild and refurbishment project which
was split into two phases. Mott MacDonald Bentley Ltd (MMB) was
successful in securing the first phase of the design and build
contract which involved improvements to the preliminary, primary
and primary sludge treatment processes.
The following elements of work were carried out as part of the
Phase 1 works.
- Online refurbishment of an existing terminal pumping station,
involving the replacement of all five existing pumps with new
variable and fixed speed, 350l/s, 42m head, immersible centrifugal
pumps;
- Complete refurbishment of the existing inlet works which has a
FFT of 3,241l/s. This included installation of six new 25mm
power-engaged back-raked coarse screens; refurbishment of the
existing spiral flow aerated primary grit removal system;
installation of new flow control / storm separation including two
new storm screens; installation of four new 6mm 2D escalator fine
screens; installation of two new 10m diameter secondary grit
detritors;
- Installation of two new archimedean screw type hydro-turbine
generators;
- Installation of six new 39m diameter radial flow primary
settlement tanks with three quarter bridge scrapers and dedicated
sludge / scum pumping stations;
- Installation of a new primary sludge treatment facility;
- Installation of three new secondary sludge holding tanks
including associated pumped and air mixing systems;
- Installation of a new process and washwater system serving the
entire site.
- Installation of a new 210l/s site drainage pumping
station.
In order to incentivise the first-tier supply chain to deliver
additional value, three major suppliers were appointed on a target
cost-reimbursable contract, and received a share of any savings
made.
MMB delivered an innovative solution to the client’s requirement
that a hydro-turbine should be situated between the preliminary and
primary treatment, in order to provide a power generation facility.
MMB consulted a number of suppliers about the ability of
hydro-turbines to cope with screened, de-gritted sewage. MMB
concluded that the best solution would instead be to use a
hydrodynamic screw pump adapted to a wastewater environment, and
subsequently worked in conjunction with the client’s framework
supplier, Spaans, to produce their first screw pump used for power
generation in a wastewater treatment works. The project was
delivered within the client’s affordability budget level.
