Water treatment involves several processes to remove impurities from water sources before public supply. These include screening, coagulation, sedimentation, filtration, aeration, and disinfection using methods like chlorination. Water can also be stored using rainwater harvesting systems that collect rainwater or greywater reuse systems that treat wastewater from sinks and washing machines for non-potable uses like toilet flushing. Factors like available water collection, required storage amounts, and costs must be considered for rainwater harvesting systems. Greywater systems vary in treatment complexity and usually include a tank, pump, and distribution system.

1. Plumbing Level 2

2. Treatment methods
Water companies are responsible for
ensuring that the water they supply is fit to
drink.
• All water must be treated before it enters the supply.
• Treatment depends on its source and impurities it
contains.

3. Treatment methods
• Water treatment involves several distinct
processes.
• Each is designed to remove different
types of impurity or contaminant.

4. Method Purpose/process
Screening Removes floating debris from raw water sources.
Primary: removes leaves, wood, dead creatures and waste paper etc.
Secondary: uses fine filters or micro-strainers to remove suspended algae and plankton.
Coagulation Removes dirt or particles missed by screening.
Uses chemicals, which may include alum.
Matter is collected as ‘floc’, which attracts other impurities. The floc becomes heavy and
removed during the next process.
Sedimentation Water is allowed to settle in large tanks.
Floc and remaining matter (sludge) sink to the bottom, leaving clear water on the surface.
Sludge is collected and removed from the tank for safe disposal.
Filtration The water is passed through filters to ensure removal of particles that have escaped the
previous processes. Filters are usually layers of sand, gravel and charcoal, but other
systems are also available.
Aeration Removes or reduces unwanted compounds, including hydrogen sulfide, carbon dioxide
and traces of iron.
Disinfection Probably the most important of the water treatments.
The water is finally treated to kill off or deactivate any bacteria.
Various methods used include chlorination, chloramines and ultraviolet (UV) light.
Ionisation The acid and alkaline content found in water are segregated by subjecting the water to
electrolysis using the natural electrical charge found in magnesium and calcium ions. This
process is normally carried out by specialist equipment in the consumer’s property.

5. Water storage and supply
Ways to save and store water. There are
two main methods:
• Rainwater harvesting – collecting
rainwater
• Grey water reuse – using waste
washing water

6. Rainwater harvesting
Rainwater harvesting is the collection of
rainwater directly from the surface(s) it falls on.
Rainwater harvesting
system with
underground storage
tank

7. • Water would otherwise have gone
directly into the drainage system or
been lost through evaporation and
transpiration.
• Once collected and stored it can be
used for non-potable purposes.

8. What purposes
could we use stored
rainwater for
around the home?

9. Benefits of a R.W Harvesting system
• Reduce demand for mains water.
• Relieve pressure on available supplies.
• Less water is taken from lakes, rivers and
aquifers.
• RWH systems can also reduce the risk of
flooding and pollution.

10. What are the factors
you need to consider
before deciding whether
a RWH system is
appropriate.

11. Factors you need to consider before deciding
whether a RWH system is appropriate. They
include:
• How much water can you collect;
• How much water you need to store;
• The costs; and
• Other/alternative water efficient measures to consider.

12. Three main type of system
Basic system.
Gravity fed system.
Direct system.

13. Cost
Systems can cost from around
£2,500 up to £6,000 depending on
the size of the tank.

14. Grey water reuse
What is grey
water reuse?

15. Greywater is wastewater from showers,
baths, washbasins, washing machines
and kitchen sinks.

16. Greywater reuse systems vary significantly
in their complexity and size.
However, most have common features such as:
• a tank for storing the treated water;
• a pump;
• a distribution system for transporting the
treated water to where it is needed; and
• some sort of treatment.

17. All systems that store
greywater have to
incorporate some
level of treatment, as
untreated greywater
deteriorates rapidly
in storage.

18. Greywater systems can be grouped according to
the type of treatment they use.

19. Direct reuse (no treatment)

20. Short retention systems

21. Basic physical and chemical

22. Biological system

23. Bio mechanical system

24. Supply and demand
On average, every person in England and
Wales uses around 150 litres of water per
day.
About a third of this is used for toilet
flushing and this proportion could
potentially be replaced by treated
greywater.

25. The guidelines in BS 8525 have
taken the standards included in
the Bathing Water Directive18
and developed values based on
detailed research into specific
applications where greywater is
to be used.

26. Water Regulations Advisory
Scheme (WRAS)
• WRAS offer independent guidance and
advice on the regulations and publish a
number of useful free to access guides.
• To manage the risk of accidental cross-
connections between potable and non-
potable supplies.