Water is a fundamental commodity for almost every single step in manufacturing and production processes across the world.
Industrial water use accounts for around 40% of total water abstractions, with the rest going towards agriculture, and personal supply.
And the water that goes into an industrial process is not the same water that comes out.
Whether it’s chemicals, organic or inorganic materials, metals, or salt, the water that goes into a process is constantly being added too, altered, or simply picking up contaminants along the way. This results in what is referred to as wastewater - an undesirable by-product of process.
As a result of the undesirable additions, industrial wastewater often requires treatment before it can be reused or discharged.
Unfortunately, due to the vast number of uses, the resulting wastewater can be extremely varied in strength, composition, and contaminants. Meaning it won’t always respond to a simple ‘one size fits all’ treatment.
Careful consideration needs to be given to determine which wastewater treatment will be the most efficient, cost-effective and adhering to any environmental regulations placed.
What is industrial wastewater?
Most industrial processes use water, some a lot more than others.
The primary industries that consume the largest amounts of water are pulp and paper, mining, oil & gas, iron & steel, food, and chemical.
Water is used across numerous activities such as fabricating, processing, washing, cooling, or transporting products or equipment. It can be used to generate electric power, to make stream for cleaning, to cool and control temperatures.
The type of industry and the specific activities and operations determine how much, and what type of wastewater is generated.
With the variance of uses of the water, comes a huge variance in the required treatment. This means there must be due consideration in place to determine what the best treatment process will be.
Depending on the source this wastewater could present some significant purification challenges - toxic materials, non-biodegradable materials, and a whole host of organic and inorganic contaminants that need to be removed.
Once removed it will ensure that industries are not only fully compliant with challenging environmental regulations but if done well companies can increase both efficiency and productivity by enabling the reuse of water in other processes as well as potentially reducing costs in waste disposal.
The best wastewater treatments will result in efficient material and reusable water recovery, a reduction of loading on downstream treatment processes, and a reduced amount of waste disposal at the end.
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Common industrial wastewater treatment processes
To determine the correct treatment you should look at what needs to be removed from the wastewater to either make it reusable or compliant for disposal.
Ask what is the physical, chemical and biological characteristics of the stream - are there high levels of oil and grease, heavy metals, biodegradable or non-biodegradable components, or high bacterial and viral contaminants that require specialist treatment for example.
Depending on what needs to be removed, and what the end goal is (reuse or disposal) there are numerous treatment processes that can be utilised.
Brine treatment is used to remove salt ions from wastewater often produced as a by-product of cooling tower blowdown, natural gas and oil extraction, reverse osmosis (RO) reject, acid mine or acid rock drainage, and from many other processes.
The most common brine treatment technologies include, membrane filtration processes, such as reverse osmosis; ion exchange processes such as electrodialysis or weak acid cation exchange; or evaporation processes, such as brine concentrators and crystallizers employing mechanical vapour recompression and steam.
Removing solids can mostly be done through sedimentation techniques that recover the solids as slurry or sludge.
Solids that are finer or have densities close to the density of water can be more of a challenge. In that case filtration or ultrafiltration can be used.
The most common ways to reduce solids include primary sedimentation (clarification), Dissolved Air Flotation or (DAF), belt filtration (microscreening), and drum screening.
Removing Oil & Grease
The wastewater produced from large-scale industries such as oil refineries, petrochemical plants, chemical plants, and natural gas processing plants often contain very high amounts of oil and grease in their wastewater streams.
The main forms of oil encountered within these wastewaters are;
- Free Oil or floating oil which can be removed by either skimming the surface in a skim tank, or by gravity separation in an API separator
Emulsified or Soluble Oil which requires chemicals to lower the pH of the water followed by the addition of dissolved oxygen or nitrogen to remove the emulsified oils as they break free (“cracking”)
Organic pollutants in wastewater can be separated into two main categories; biodegradable organics, and non-biodegradable organics.
Biodegradable organic material comes from plant or animal origin and can normally be treated using extended conventional sewage treatment processes such as activated sludge or trickling filter.
Synthetic organic materials which include solvents, paints, pharmaceuticals, pesticides, products from coke production etc. can be much more challenging to treat.
Treatment methods are often specific to the material being treated and include advanced oxidation processing, distillation, adsorption, ozonation, vitrification, incineration, chemical immobilisation or landfill disposal.
Interested in what contaminants might have worked their way back into your drinking water? Read our article - 5 Concerning Contaminants Found In Your Drinking Water.
Wastewater from acid manufacturing plants or industries where acids are used as raw materials or catalysts will inevitably contain acids in the waste stream.
Removal of these pollutants require strategies involving, ion exchange, adsorption, solvent extraction, membrane separation, reactive distillation, reactive extraction, membrane based solvent extraction, emulsion liquid membrane separation etc.
Are you ready to find out more about the aeration power behind some of the most vital wastewater treatment processes? Download our wastewater brochure.