Water treatment

South East Water treats the drinking water it supplies to the highest standards to ensure it is fresh, wholesome and safe 24 hours a day, 365 days a year.

The type of treatment depends on the source of the water but can include several stages of mechanical and chemical cleaning. About three-quarters of the water supplied by South East Water is pumped from underground aquifers. Because it has been filtered through many layers of chalk or sand it is already of high quality and only needs to be disinfected with chlorine.

Water taken from rivers and surface reservoirs has been open to the environment and requires additional treatment before being chlorinated and pumped to customers’ taps. Tests are carried out to make sure that the water is pure and meets strict European standards before it leaves the treatment works.

Below is a brief description of the main types of treatment steps that South East Water employs in varying combinations, depending on the water source:

Storage
Water can be held in storage reservoirs for hundreds of days before it is pumped to the works for treatment, which allows debris and solids to settle to the bottom and the sunlight to break down organic material and kill bacteria.

Screening
As the water is collected for treatment it is passed through fine screens so larger solid material such as sticks and weeds can be removed.

Primary Treatment
At the water treatment works, ozone is bubbled through the water, which reacts with any impurities. A form of iron, called ferric, is then added which forms small particles to attract the impurities from the water. These particles are called floc.

Clarification
During clarification, the floc is slowly stirred to increase the size of the particles so they are easier to remove. This is done in a clarifier where the floc sinks to the bottom and is taken out.

Filtration
Water companies use several types of filtration, such as sand or rapid gravity filters, which sieve suspended material from the water. Slow sand filters also have a biological action which encourages bacteria to grow, which in turn breaks down the organic compounds in the water.

Aeration
This process can be used to remove unwanted compounds (such as hydrogen sulphide and carbon dioxide) from water, or oxidise dissolved metals such as iron in order to ease subsequent removal.

Advanced Treatment
Some water also undergoes ozonation with a process using granular activated carbon (GAC). During ozonation, ozone gas is bubbled through the filtered water to disinfect it and help the GAC remove pesticides. This treatment improves the taste, odour and clarity of water.

Disinfection
Chlorine is used to disinfect all water supplies, to ensure potentially harmful micro-organisms such as bacteria are killed and to keep it safe on its journey from the treatment works to your taps.

Sludge Treatment
Wastewater is produced during the treatment processes containing water, impurities and chemical particles. This is treated to return the clean water to the environment and recycle the solid matter into a sludge cake for use as an agricultural fertiliser.