Background
Lewis Civil Engineering was chosen by Welsh Water to drain down Llanishen Reservoir, Cardiff to test the existing scour valves. The reservoir is being drained down at a flow rate of circa 40m3/hr and Siltbuster were called in to keep the discharge into a nearby brook within consent.
The Overall Objective
To provide a temporary water treatment solution to treat the solids present in the reservoir water prior to discharge to the surface watercourse. This had to be operational 24 hours a day and be of consistent quality.
Solution
Siltbuster installed a multistage system, consisting of an HB50 settlement tank, an MT8 mix tank and two-stage chemical dosing system. Sensors were used on the system inlet to ensure pre-treatment chemicals (coagulant and flocculant) were only introduced when the Total Suspended Solids (TSS) content of the feed water exceeded the 60mg/l discharge target. Outlet sensors measuring water quality at all times. A GSM module sends a text message to alert users of an auto-shutdown.
This solution ensured a TSS of less than 30mg/l and pH of between 6 and 9.
