Effluent Treatment Plant
by Rami Elias Kremesti M.Sc., CSci, CEnv, CWEM
Introduction
An effluent treatment plant (ETP) is a facility that treats industrial wastewater to remove pollutants before it is discharged into the environment or reused. The process is crucial for sustainable recycling of waste water and preventing water pollution and protecting ecosystems, and it is mandatory and regulated for many industries like chemical, textile, plastics recycling, oil and gas, metallurgy, mining and food processing. The treatment involves stages like screening, equalization, pH adjustment, biological treatment, Physico-chemical treatment, UV treatment, filtration and membrane treatment to ensure the effluent meets safety and environmental standards.
Industrial Pollutants
Suspended solids, oils, and grease: Removed through physical processes like screening, sedimentation, and flotation.
Biodegradable organic matter: Removed by biological processes like activated sludge and trickling filters.
Refractory organic compounds: These can be challenging, but advanced methods like using ponds and wetlands, or adsorption with activated carbon, can be used or as a last resort incineration.
Heavy metals: Removed via chemical precipitation, filtration, and adsorption using materials like chitosan, filtralite or bentonite.
Nutrients: Nitrogen and phosphorus compounds are removed through biological and chemical processes.
Pathogens: Removed through disinfection, often with chlorine, and advanced treatment methods.
Micropollutants: These include pharmaceuticals, hormones, PFAS, and pesticides. They can be removed using advanced techniques like membrane filtration (reverse osmosis, nanofiltration), adsorption, and AOPs.
Acids and alkalis: Removed by neutralization processes.
Treatment Processes:
screening, equalization,
Separation of Oil from Water
DAF – Dissolved Air Floatation
pH adjustment,
Filtration: sand filtration, active carbon filtration, Multi media filtration
Membrane treatment: MBR/UF/NF/RO
Physico-chemical treatment: disinfection, coagulation/flocculation/gravity settling/AOP
Biological treatment,
UV treatment,
Evaporation
Sludge Dewatering/Drying/Incineration
Zimmpro Process: The Zimpro process is a type of wet air oxidation (WAO) used for treating industrial and municipal wastewater and sludge. It uses high temperatures (150-330 C) and pressures (2-20 MPa) to oxidize organic matter in the presence of air or oxygen, breaking it down into water, carbon dioxide, and other simpler, more biodegradable compounds. Developed by Fred T. Zimmermann (UK chemical engineer based on London), the process is often implemented in a bubble column reactor, where air is bubbled through the liquid waste to facilitate oxidation.
Examples
A plastics recycling facility (PRF) that I worked at near Bristol had to treat waste water generated by washing plastics before recycling. The water was dirty, with high SS, BOD (from residual foodstuffs) and COD (from surfactants used for washing), sulphates and had a high pH due to the use of caustic soda to de-label the plastic waste.
The treatment process that was proposed, after mesh screening, used CO2 to neutralize the high pH. This is an expensive solution but does not use harsh caustic chemicals and is environmentally friendly as it captures industrial CO2. The next process step was DAF = Dissolved Air Floatation to remove SS and scum. To remove BOD, a biological step was used. Finally RO was used to remove residual COD and TDS/Sulphates. For the complete presentation on this process, click here.
KCM Metals in Plovdiv Bulgaria is a large lead smelter that has to treat its waste water to remove heavy metals before discharge to local waterways. They use high pH lime precipitation to achieve this. They also have low pH sulfuric acid polluted waste waters that they treat through Calcium Sulphate precipitation.
For a presentation on textile waste water treatment click here.
For Oil and Gas waste water treatment, click here.
For Mining Waste Water treatment, click here.
For landfill leachate waste water treatment, click here.
Pulp and Paper
Food Processing Waste Water Treatment
Semiconductor Waste Water Treatment has to deal with Fluoride pollution because Hydrofluoric acid is used in etching processes. Fluoride can be precipitated by reacting with Calcium. Read our article on semiconductor waste water treatment.
Consultancy On ETP Design
To design an efficient and cost effective ETP, one must know the different pollutants in the water and how to treat the water to remove them. An in-depth knowledge of micro-biology and chemistry is many times needed. Building the system yourself will most likely save you money than buying a whole system as over-heads/mark ups are high.
RO systems also require operational and maintenance know how so training is a must otherwise the RO systems foul or scale up.
UK Regulatory Framework
The UK Environment Agency is the primary regulator for effluent discharge in England, issuing permits, monitoring compliance, and taking enforcement action. Ofwat, the economic regulator for the water and sewerage sectors in England and Wales, also plays a role by investigating issues related to sewage treatment works/discharge to sewers. In Northern Ireland, the Department of Agriculture, Environment and Rural Affairs (DAERA) is responsible.
Major Effluent Treatment Companies
OVIVO
Hager El Sasser
Veolia
ClearFox
EnPure
Xylem
Huber Screens/Sludge Dewatering/MBR
Royal Haskoning
IDE – Israel
Saur/Nujhuis
Conclusion
In order to achieve compliance and protect the environment, any industry that generates waste water needs to treat its effluent in an ETP.
About the Author
Rami Elias Kremesti is a UK chartered water treatment specialist with a background in chemistry. He has worked in the water treatment field for over 20 years. He spent ten years working on power stations worldwide and the next ten years working in various industries such as sewage treatment, building services, plastics recycling and drinking water treatment.
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Rami Elias Kremesti Portrait