Sewage systems (FOI)
Sewage systems (FOI)Produced by the Freedom of Information office
Authored by Government of Jersey and published on 30 August 2019.
Prepared internally, no external costs.
I’ve been looking at issues regarding CSOs (Combined Sewage Overflows), of which we have experienced several in Jersey this year, and I notice that there are available various systems in place to screen out more solid materials (vortex separators like The Swirl Concentrator, the Fluidsep® and the Storm King) and while some outflow occurs,
I wonder what system Jersey uses to screen out the worst of the material before releasing overflows to the sea?
Also are any filtration systems like Fuzzy Filter® used before material is released to the sea. I understand that a synthetic medium filtration like a Fuzzy Filter® can treat large amounts of water with high flow rates.
I also note that the cavern is no use because of the location of the pumping system (on the east of the Island) and the water flow rates. Are there any plans to increase the sewer pipe sizes? Portland has recently implemented a "Big Pipe" system to maximise the flow capacity through the city and reduce CSOs.
Finally, are there any plans to separate at least some of the groundwater runoff from the sewer systems?
In comparison to the UK, the flows, pipework and footprint of our pumping stations are very small. Therefore, there is no room to install proprietary systems such as those referred to in the question. However, the pumping station at Le Dicq is fitted with coarse 40mm filter screens.
We are not using any filtration systems, such as Fuzzy Filter due to limited space at our CSOs.
There are currently no plans to increase the size of the sewer pipes, however, work was carried out in the 1990’s to improve the overflow storage capacity on the east coast chain. We installed additional tanks at nine of the major foul pumping stations on the east coast which resulted in an increased storage capacity of 3565 cubic meters.
We have improved the intelligence in the network to allow all the upstream stations to utilise their overflow capacity by starting and stopping pumps as necessary which reduces the risk of discharges into the sea.
The new sewage treatment works will provide a further 5855 cubic meters of storm storage tanks when it comes online in 2023.
We are investigating other storage areas, but these are likely to be located in the west of the Island.
We have identified several schemes to separate surface water from the foul sewer network and have submitted funding bids as part of our business cases for 2020-2023.