Sewage Treatment Expert High Wycombe
Introduction
Hello, my name is Rami Elias Kremesti, I am a CIWEM chartered sewage treatment specialist based out of High Wycombe, UK and serving the greater London area. I have a Masters degree in chemistry from the USA and I have been working in the water treatment field for 20 years. You can view my CV here.
Sewage Treatment Basics
Sewage treatment is the technology which purifies waste water from bathrooms and showers. Some showers are connected to a grey water treatment system which can treat the grey water to irrigation or toilet flushing standard. Sewage Treatment Systems basically start with some kind of sieve/rake to remove the large debris like sanitary pads/diapers/wipes, etc. After that you can have a finer sieve screen.
Once the large debris are removed, you need to work on 7-8 major parameters:
- Grit
- Fat Oil and Grease (FOG)
- BOD = Biodegradable or Biological Oxygen Demand
- COD = Chemical Oxygen Demand (Non-Biodegradable organics)
- SS = Suspended Solids
- N = Total Nitrogen
- P = Total Phosphorus
- Bacteria Load (optional)
For a complete discussion of sewage treatment basics, please refer to my presentations: Package Sewage Treatment Plants, Septicity and Odours In Sewage, Membrane Bioreactors and Anaerobic Digestion.
Process Steps:
Sewage Treatment is divided into 3-4 major process steps:
Primary Treatment:
Removes major grit, SS and settleable BOD plus the FOG floats on top. In this stage we normally use some kind of Primary Settling Tank (PST). Some of the COD is reduced in this step as FOG contributes about 30% to COD.
Secondary Treatment:
In this step we treat the biodegradable organics in the water, the BOD. Aerobic bacteria are used which “feed” on the organics and multiply. Also nitrifying bacteria convert ammonia to nitrate in this step.
Sludge is produced in this process which is aerobic and requires aeration. If Total Nitrogen reduction is required, then the effluent from this stage which is rich in nitrates needs to be treated in an additional Anaerobic step in which denitrifying bacteria convert the nitrate to nitrite, then nitrous gas, and finally to nitrogen.
Part of this stage is a settling tank/membrane filtration in which sludge and SS settle out. Sometimes between the aeration step and the settling step we dose Coagulants to settle out more SS and Phosphate.
Tertiary Treatment:
Here we filter/disinfect the water. More BOD is removed especially the particulate kind as well as more SS is removed. Chlorine is added to kill pathogenic bacteria and lower E Coli especially when the receiving water body is used for recreational bathing. UV systems can also be used to reduce bacterial counts without using chemicals.
Quaternary Treatment (Optional)
In this step sometimes drain fields/reed beds are used or in larger municipal plants, special water treatment processes like AOP or Active Carbon Filtration are used to remove pharmaceuticals, biocides, insecticides, antibiotics and other persistent and forever chemicals.
Services Offered
I offer consulting services to help you with your sewage treatment project. We can help with permitting, design, contractor selection, supplier selection or even help with malfunctioning STP’s or STP’s not meeting effluent requirements.
We look forward to your query.
Kind regards
Rami Elias Kremesti M.Sc, CSci, CEnv, CWEM
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