SITE PREPARATION


f the diffusers are not located in the tank correctly, such as lying on their side or one on top of the other, some of the air holes may seal up oer time as air will always take the path of least resistance which is from the highest point. This again reduces the uality of aeration into the treatment zone and creates more back pressure on the compressor, forcing it to work harder and resulting in a shorter design life. Tanks can een be installed the wrong


way round, with the inow going into the outlet which will obiously cause issues from the moment go, and if tanks arent leel, graity ow into or out of the tank will be affected. nd if the wrong backfill material is used, een the most robust tank may be damaged by sharp stones or bricks.


diffusers that sit in the bottom of the tank and release small air bubbles into the efuent which hae not been connected properly, or air hoses that kink. This affects the most important part of the treatment process – the uality and uantity of aeration. f the dissoled oygen leels in the treated efuent are low, this will result in odours.


Some systems hae not een been switched on f this was discoered say si months after the system should hae been commissioned, the plant would only hae been acting as a septic tank, a storage essel with no capacity to treat its contents, for all that time. Contemporary wastewater treatment plants run on two -hour or four si- hour cycles so een if something as basic as checking the date and time are correct is not done, this will affect its ability to function properly.


nd let us not een talk about drainage fields en though these are inisible once installed, if they hae not been sized and designed correctly, any issues will soon become etremely isibleas well as etremely smelly.


David Stagg is technical manager for Graf UK


38 www.sbhonline.co.uk


jul/aug 2023


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