Flagging-up improvements

During the 1999 bathing season, bathing water quality at Newhaven failed to

meet the mandatory standard. The town’s bathing water is the responsibility

of Southern Water, which reversed this trend in 2001, achieving a 99% pass rate.

Of 74 beaches monitored in Southern’s region, 73 have passed the mandatory standard.

Just one failed, in north Kent, where there is an issue over discharge from

a private cistern. In total, 54% of the beaches are also meeting guideline standards

promoted by the Environment Agency. This is a huge improvement when you consider

that in 1988, when Southern began its capital investment plan, only 40% of beaches

were meeting the mandatory standard.

It was decided early in the design stage that Newhaven STW would utilise a

compact gravity settlement system, the spiral separator (WWT September 2001),

which requires just 3-4% of the area used by conventional treatment processes.

Main contractor Miller Civil Engineering Services (now Morgan Est) and process

contractor Purac had a relatively smooth ride when it came to construction,

only an environmental survey of the site threw up problems. It was found that

land between Newhaven and Lewes, where Edmund Nuttall would be laying pipeline,

was inhabited by great crested newts, a protected species. Special netting was

erected to prevent newts entering the site and construction work was put on

hold until their breeding period was over.

Local residents’ concern was alleviated when Southern held public exhibitions

to detail its plans. To soften the visual impact the water company will also

landscape the area around the Newhaven site. Construction work began in October

1999 and consent was met in December 2000. The project took eighteen months

from commencement to completion. The £20M spent on the project included

all transfer work on the 11km pipeline and pumping station at Lewes.

Newhaven can now deal with 28.5Ml/d of wastewater, achieving 75% COD and BOD

removal across the plant and turbidity of 100ntu. The use of spiral separators

has revolutionised the treatment process. Driven by hydraulic powerpacks, they

are energy efficient, cheap to run and require low maintenance. They currently

achieve 5% solids removal in contrast to conventional technology in which 1-2%

can be expected. Southern Water is continuing testing in order to refine the

process further. The company admits it worked hard to get such efficiency in

the beginning – getting settings right, achieving the correct flow and coping

with influent levels. But from the outset Southern Water recognised the spiral

separator’s potential, investing £2M to develop the technology.

Southern anticipates the Newhaven plant will have a 15-20 year working life.

During this time the company sees no reason why the spiral technology should

not become commonplace throughout the industry. It even predicts a spiral separator

for final as well as primary settlement.

Nearly 40 miles along the coast, Ford aerodrome was chosen as the ideal site

for another STW. Ford was built to meet the Urban Wastewater Treatment Directive,

before its construction preliminary treatment only existed at headworks in Bognor

and Littlehampton. One of Southern’s largest plants, Ford STW provides treatment

for a combined population equivalent of 150,000, for the separate catchments

of Littlehampton and Bognor Regis.

The works consists of three primary settlement tanks, 30m in diameter, secondary

phase aeration lanes and four 30m diameter final settlement tanks. Ford runs

two process streams. Not only is Southern making a dramatic improvement to water,

it is producing a commercially viable sludge product. Sludge drawn off at various

stages in the treatment process then goes through anaerobic digestion. The digested

sludge is then processed from a liquid into a cake using centrifuges. The final

cake is 25% dry solids.

This material is sent through a further drying process to produce fertiliser

pellets. Ford, a regional sludge recycling centre, also deals with sludge from

satellite plants. It can handle 8,000 tonnes of dry solids a year, of that,

approximately 4,000 tonnes is imported as either cake or liquid.

A number of sites were assessed before Ford was chosen. Existing works in Littlehampton

and Bognor were obvious possibilities. In essence, this would have been Southern

Water’s cheapest solution. However, Ford stood out because it had potential

as a green field site. It was an old aerodrome, so space was not a constraint.

It was also an acceptable distance from the two head works. Once plans were

announced Southern met with local opposition, similar to that raised in Newhaven.

As well as running exhibitions, the company arranged a public meeting. Site

visits to operational STWs were organised for a council committee, to help them

understand how problem areas, such as odour, would be overcome. Local people

were consulted during the construction phase through a liaison group initiated

by the county council. Ultimately only three meetings took place because interest

waned once people were reassured of Southern Water’s intentions.

The project underwent two planning phases. Following the outline phase, the

water company made dramatic changes to the scheme which involved a further planning

phase and detailed application. This was largely due to a rearrangement of the

site to provide for secondary treatment. A series of design reviews were necessary

to comply with the Urban Wastewater Treatment Directive. Southern originally

intended to use a chemically aided primary settlement (CAPS) process, which

satisfied the directive, but met with local opposition because of a question

mark over standards of treatment. The government initially approved CAPS treatment

because effluent would be discharged into a high dispersion area, but after

residents met with Mr Meacher, the government reversed its decision, taking

away the natural dispersion provision, forcing Southern to provide secondary

treatment.

The second phase of planning generated some 30 conditions. These included a

12m height restriction on all buildings, which meant the dryer building had

to be part buried. There is a 10m restriction on any future development, less

than the general provision of 15m. Extensive landscaping and tree planting has

been carried out around the site, to further limit visual impact. Construction

traffic could only use the A259, a lower coast road, and operational traffic

is not permitted to use the route through nearby Arundel in case it worsens

an existing bottleneck. There are stringent odour emission standards, hydrogen

sulphide levels must not exceed 1.3ppb at, or beyond, the boundary of the plant.

To achieve this the plant is fully enclosed, the sludge treatment system and

primary settlement tanks are covered and air is ducted back to a two-stage chemical

scrubbing system.

In addition, Southern Water was required to undertake an extensive archeological

survey of the site, before construction work began. The company spent considerable

time with the county archeologist and a specialised firm of archeologists. A

study of the proposed STW site unearthed artifacts from roman, bronze and iron

age periods, making it the second most important archeological site in the south

of England. The old aerodrome also relinquished an unexploded bomb, which required

a controlled explosion.

Work on the plant began in May 1999 and it was receiving flows for treatment

in October 2000, two months ahead of schedule. Plant design includes provisions

for future demand. Southern Water has consent to 2005, but a design horizon

to 2015.