How to Remove Phenols from Wastewater
How Nyex effectively and safely removes phenols from specialty chemical wastewater to below measurable levels.
What are phenols?
Phenols are similar to alcohols but because they form stronger hydrogen bonds, they are more soluble in water and thus are more likely to be unwanted constituents of industrial wastewater.
In its simplest form, phenol is known as monohydroxybenzene (benzenol or more simply, carbolic acid) and was reportedly used as the first surgical antiseptic by British surgeon Joseph Lister in 1865.
However, medicine has come a long way from 18th Century ‘kill or cure’ treatments and although phenols are now widely used as a disinfectant in cleaners and mouthwash (in low concentrations of course) a small amount on the skin in concentrated form can cause severe burns and could eventually lead to death.
Why do Phenols need to be removed from wastewater?
When phenol mixes in water, it can combine with other compounds to form extremely hazardous compounds which are harmful to aquatic and human life. For this reason, the US Environmental Protection Agency (EPA) and the EU have listed phenolic compounds of pollutants of priority concern.
So chemical manufacturers who use phenol need to be very careful not to discharge phenol, so to avoid environmental bad press and fines.
Fortunately, the Arvia Nyex™ system is perfectly suited to remove these compounds down to below measurable levels.
How do phenols get into wastewater?
There are two main ways by which these unwanted compounds can appear in industrial wastewater and both are an unavoidable by-product of many manufacturing processes.
Water is used in the production process that also features phenols.
Any washdown or maintenance routines will add to concentrations of phenols in water used.
With the increasing cost of water – and sometimes even its availability being under threat – it makes sense to purify plant wastewater as much as possible. Many companies are starting to consider the possibility of ZLD (zero liquid discharge). Nyex Rosalox™ helps to make this possible.
Removing phenols from wastewater
Most companies Arvia deals with are of a sufficient size to have trade effluent consents in place that will specify wastewater purity and so they are concerned about adhering to limits as well as minimising adverse CSR exposure.
Our Nyex Rosalox™ treatment system overcomes the issues often experienced with traditional AOPs (advanced oxidation processes) and provide a robust and effective solution for the removal of organics. It works through a unique combination of adsorption and oxidation and can be placed at various points in many industrial water polishing processes.
As well as efficiency and high performance, the over-riding advantage of Nyex™ systems is that the process leaves no residue, resulting in minimal maintenance, maximum up-time and no toxic residue requiring removal and incineration (itself a major cause of pollution.)
Our new-generation Nyex Rosalox™ systems can reduce phenols to below the limit of detection in many specialty chemical processes – literally to parts per trillion. In many applications has been shown to deliver COD polishing from >300 mg/L to below LOD.
Protecting other water treatment processes
Biological and reverse osmosis water cleansing are ideal for removing other unwanted compounds, but the damage that phenols can do to a biological or RO system (and the relative ineffectiveness of removal of phenols in these systems) mean that they need to work in tandem to deliver the best results.
So in many cases, we’ll recommend a more modular approach with Nyex™ systems positioned in various key places in a plant to address these issues. All Arvia Nyex™ systems are scalable with a small footprint and no moving parts, requiring no chemical dosing. Additionally, they do not generate toxic sludge like many other water treatment systems.
GAC vs Nyex
Granular Activated Carbon (GAC) is often used by the specialty chemical industry because it’s also reasonably effective at reducing concentrations of phenols. However, unlike Nyex™ systems, GAC has some major issues which can make it less environmentally friendly and less cost-effective.
1
The carbon bed needs replenishing from time to time; this means taking the equipment out of service leading to potential production suspension or changing over to a parallel system – which of course has its own implications in terms of CapEx. Changeovers need scheduling and are a potential problem if they don’t happen regularly.
2
If too much phenol is sent through a GAC it may become saturated before it is due to be refreshed, which leads to a breach of discharge certifications.
3
It’s usual to insure against over-saturation (and any resultant environmental fines) but it adds to the OpEx considerably.
4
If a plant only has a very small GAC process and the medium is only changed twice a year then that’s probably the most cost-effective solution. But a large GAC installation that has (say) its medium changed a few times a year will cost more in OpEx than an equivalent Nyex™ system that only needs topping up annually and has no waste.
5
GAC sounds eco friendly and fairly passive, but in truth it’s neither. Trucking away the spent carbon is clearly not environmentally friendly. Also, to refresh the carbon takes a lot of energy, so essentially there is no net eco benefit.
Nyex as a complementary water treatment technology
Conventionally, in many industries, Nyex™ polishing systems are placed as a tertiary line of water treatment behind mechanical and biological systems.
However, when dealing with high concentrations of phenols, the Nyex™ system often needs to be placed second in line after mechanical filtration, otherwise phenols will destroy many of the active parts of a biological or RO system and render them ineffective. (In RO systems the expensive-to-replace membranes can be easily damaged by phenols.)
Nyex works as a complementary technology in most cases, removing specific recalcitrant and harmful organic compounds, whilst protecting existing processes like biological or RO.
Benefits of Nyex
As a consequence of the way it works, combining absorption and oxidation, Arvia’s Nyex™ system is particularly effective in treating phenols at both low and high flow rates. In both lab and real-world tests, we’ve achieved excellent results down to parts per trillion – essentially below LOD.
The main benefits are:
1
No waste
Arvia’s latest Nyex Rosalox™ system combines adsorption and oxidation into one space-efficient system, resulting in targeted and complete destruction of contaminants – all without the production of secondary wastes.
2
Dosing not required
Using Nyex™ avoids any handling or storage issues with chemicals, H&S training for maintenance teams, COSHH compliance and risk assessment paperwork as well as negative environmental impacts.
3
Onsite treatment
Nyex™ negates the high costs and negative environmental impact of having sludge or media transported and disposed of regularly. Our Nyex™ media is simultaneously regenerated during the treatment process. All a Nyex reactor needs is a minimal top up annually.
4
High up-time
There’s no need to stop processes to clean or replace fouled membranes as you’d have if only using a RO process.