On Thursday 20th August, 13 members and one guest attended the tour (see photo), which started with a substantial talk about Southern Water and its remit. We were then issued with hard hats (c/w with ear phones for listening to our guide), orange tabards, and gloves, before touring the plant. The plant is big, and consists of a covered area (c/w with grass roof – mown once a year) about 250m long, plus various very large outdoor tanks etc.
Click on image to see larger view.
We were shown a map of the ‘South East UK’ – see attached map (above) and foot notes. It is interesting to note not only the pockets of Southern Water (SW) responsibilities within what is mainly South East Water, and vice versa, but also the fact that said responsibilities may cover the supply of water, or the processing of waste water, or both. Thames Water also overlap some of the area. Said map helps explain why one household may experience a hosepipe ban, while its neighbour may be free of such a ban, depending on where the relevant authority is sourcing its water.
The Peacehaven site processes the waste water (see below) from some 300,000 persons living in, working in, or visiting Brighton, Hove and the surrounding areas. It went operational in 2012 and supercedes the original sewage processing works at Portobello (Telscombe Cliffs). The latter used to carry out limited screening with no associated biological treatment, before discharging effluent into the sea. It is now a pumping station for the wastewater coming from Brighton, and also provides the gateway to the 2.5km discharge pipe for the (almost pure) treated water from the new Peacehaven plant.
During periods of heavy rainfall, the volume of water entering the system can increase dramatically. Historically, water companies have been permitted to use storm overflows to prevent the sewer network and treatment works from becoming overwhelmed. These overflows discharge heavily diluted wastewater to the sea or rivers during exceptional conditions.
To reduce the need for storm overflows, Southern Water is investing in a range of measures, including:
These measures help increase treatment capacity, reduce pollution risks and improve the health of local rivers and coastal waters.
After getting kitted out, we proceeded past the first piece of plant which was in fact a group of powerful fans that blew air into the final (aerobic) stage of processing. (See below.) We then came to a concrete lined ‘pit’ (about 25m deep) which had 4 large centrifugal pumps at the bottom. These pumped the incoming effluent to the upper floor, where it proceeded through the facility under gravity. First up was the screening plant for gravel (goes to make roads), paper and fabric (goes to cover landfill sites), and fat and oils (goes to help feed the anaerobic bacteria in the digester downstream). We were shown all sorts of toys etc that have come out of the screening, including a very large (1.5m round?) teddy bear which did not even reach the screening plant, as it had jammed up one of the incoming feed pumps.
After screening, the effluent goes to large settlement tanks fitted with ‘Lamella’ devices. These consist of ‘cubes’ of angled deflection surfaces which slow the flow and greatly assist in the deposition of sludge which then settles to the bottom of the tank and is pumped into the anaerobic digestion tanks. These in turn further break down harmful bacteria into:
a) methane-rich biogas, which is used in combined heat and power engines to generate electricity (currently 1150kW – soon to be 2x1066kW) and heat for the treatment works; and
b) treated biosolids, which can be recycled to land as a soil conditioner where regulations permit. Meanwhile the liquid from the Lamella tanks goes to bubble-ventilated aerobic tanks which are filled with millions of expanded polystyrene balls (size of peas), which, in turn, provide a large surface area on which the aerobic bacteria do their work. And finally out comes near ‘pure’ water which is discharged out to sea. The purity is monitored by Environment Agency inspectors who carry out spot checks.
It is also worth noting staffing arrangements. Apart from our 2 guides, the plant has 6 employees, of which 3 are on duty at any one time. But there is also much telemetry going on, with sensors sending readings to SW HQ in Durrington.
Our guide is holding a pice of 'cake' that is the final solid output from the plant. This is used on farms.
The Peacehaven plant is a modern example of best practice, which shows up shortcomings in older plants. SW apparently have a £1.5billion budget to improve/replace older plants, pipework and processes. SW are also giving more attention to tracking down faulty soil water connections and advising others on what to do, unless the remedy is simple and cheap in which case SW may be able implement it.
As regards the technology supporting the ‘visit’ itself, 2 things are worthy of comment. Firstly, when the guide wanted feedback, eg ‘what did we think of the visit?’ or ‘what was our impression of Southern Water?’ each person had to hold up a square card with a scanning code on it, which, depending on which of the 4 edges was uppermost, denoted each person’s respective answer. Our guide then scanned the visitors displaying their cards and subsequently compiled a list of answers.
Secondly, the earpiece speakers on our hard hats, seemed like a brilliant idea for when our guide wanted to tell us things on our tour, but was hampered by noisy machines working in the background. Also they needed quite a lot of ongoing adjustment by our 2 guides - but a great idea yet to be perfected.
Overall, it was a most informative and interesting visit – with no charge. Visits are not limited to organised groups such as the RCEA, or school children. Any member of the public can contact SW who in turn will organise groups of between 8 and 15 people to form a viable party – albeit one that does not ask as many questions as a group of mainly retired engineers.
Report by Mike W