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 Website - Infor - Sewage Treatment​​​

What is Sewage? 

Once we have used water we pull the plug from the sink, flush the toilet or pour it down the drain where it 
enters the sewerage system. Sewage is the water found in sewers. It can be a mixture of water which has 
been used for a variety of purposes in the home, at work or in leisure activities, and water used for business 
and industrial purposes. 

Sewage contains a wide range of waste products. It contains 

• solids suspended in the water 
• things dissolved in the water 
• bacteria and other sewage micro-organisms living in the water. 
On average each of us generates 275 litres of sewage a day with over 99.9% being liquid and less than 
0.1% solid. 
The Sewerage System 
The sewerage system is the network of sewers, pipes and pumps that lie unseen beneath virtually every 
road and street that carry sewage from where it is produced to the sewage treatment works to be treated 
and cleaned. 

There are two types of sewerage systems: 

• Combined sewers – carry both sewage and rainwater in a single pipe. 
• Separate sewers – use two pipes. One (called the Foul Sewer) takes sewage to a sewage treatment 
works and the second (called the Stormwater Sewer) carries rainwater straight to a nearby wadi or the 
sea, as rainwater does not require treatment. 
• Abu Dhabi - we have separate sewers. ADSSC owns and manages the foul sewers (carrying 
sewage) and the Municipalities own and manage the stormwater sewers (carrying rainwater). 

Why is sewage cleaned? 

Sewage treatment works remove things from sewage that could harm the environment, so that the water 
can be reused for irrigation purposes, or returned to a wadi or the sea. If they weren’t removed then the 
water could not be used for irrigation and would pollute the wadi or sea, reducing oxygen levels which are 
vital for the health of the wadis and sea. 

There are six stages in sewage treatment: 

• Preliminary: this removes large floating and suspended solids, sand and grit 
• First settlement: this removes small suspended solids (called primary sludge) 
• Biological treatment: removes dissolved items through the action of micro-organisms 
• Second settlement: removes small suspended solids (micro-organisms) (secondary sludge) some of  which are returned to the biological phase 
• Tertiary treatment: removes very fine solids and disinfects the water so it is fit for reuse by irrigation. 
• Sludge treatment: treats the sludge produced by treatment stages so it can be recycled Tested 

At all points along the way the water is continuously tested and monitored to ensure the right amount of  chemicals are being added and that the sewage is being treated so that it is clean enough to be returned to  the environment for reuse. ​

 Website Info Grease

Fats, Oils and Grease – Don’t give yourself a headache. 

Do you get rid of grease, fat or oil down your sink? 
Did you know that you could be causing yourself a real problem? 
Read on to find out why . . . 
Grease, fats and oils are a real problem in drains and sewers. Quite simply they harden and block pipes. 
This can lead to sewers backing up and flooding homes, businesses, gardens or streets. 
Grease, fats and oil usually get into the drainage system via the kitchen sink. When grease comes into 
contact with detergents like washing up liquid and hot water it dissolves. The liquid goes down the drain and 
as the pipes are deep underground they are cold, this cools the grease, which sticks to the side of the pipe 
and hardens. Some detergents claim to dissolve grease and it may pass through your pipe but it will settle 
elsewhere in the sewer network. 
If the blockage occurs in your drain this can be very unpleasant and you will have to have it cleared which 
could be expensive. If the blockage occurs in the sewer it could cause sewer flooding which can be very 
unpleasant for those affected and expensive to clear. 

How to avoid the headache: 

To dispose of fats and grease: 
• Allow the grease to cool and harden. 
• Scrape it into kitchen paper, old newspaper, or packaging. 
• Put it in your bin 

To dispose of used cooking oil: 
• Let it cool down. 
• Pour it into a used container. 
• Put it in your bin