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Treatment of phenols in a wide range of industrial wastewater
Phenols exist in a wide variety of industries, including the pharmaceutical industry, oil & gas production, life-science, food packaging, foodstuff and multiple process industries. They are also common aroma additives in a large number of beverages. Phemols versatile properties and active functions have made them one of the most common industrially applied class of compounds in the world. However, due the highly potent characteristics, their properties also make them subject to scrutiny and restrictions are accelerating pertaining to the release into and concentrations in the environment. The US EPA restricts phenols to 5 ppm if released into the sewage network and less than 1 ppm if released into inland waters. Some phenol compounds are considered hazardous and their human exposure limits can be found in both ppm and ppb levels. Luckily, phenolic pollutants can be managed and phenol based contaminants in industrial wastewaters can be completely eliminated – if done right.
What are phenols?
In its most basic form, phenol is also referred to as Benzenol, ie consisting of benzene with a hydroxy (-OH) group. It is also called phenolic acid due to its slightly acidic properties. Many variations of phenol can be derived using various chemical manufacturing methods. Some phenols are toxic and can affect the central nervous system – hence its use must be carefully controlled.
Phenolic compounds as pharmaceutical substances
In spite of their general toxicity, phenolic compounds are frequently found among common pharmaceuticals such as Paracetamol (active substance in pain killers) and Propofol used in intravenous anesthesia among many others. In these compounds, the phenolic parts may constitute on of the several active parts.
In small doses, phenolic pharmaceuticals are widely used in very small levels, albeit its toxicity in high concentrations. Their chemical structures can be found in the picture below.
Bisphenol-A in plastics
Bisphenol-A has been used widely in the manufacturing of plastics and is one of the most commonly found substance in every day life due its straightforward synthesis methods by condensating phenol and acetone. Although it does not accumulate in the body, high exposure during long periods of time may cause disruption in the reproductive system where it has been found to mimic estrogen.
It has therefore been widely banned in some specific products but can still be found in many plastic products. This is apparent from water analyses of municipal wastewater along with analyzing and treating pharmaceutical residues, which Mellifiq has conducted at Uddebo in Luleå.
Paracetamol is one the most common phenolic pain killers used daily by millions of humans every day globally. It can be identified as a phenol from the hydroxy group with an aromatic ring.
Bisphenol-A. One of the most prolifically manufactured phenol compounds, found in food packaging and plastic bottles. Bisphenol-A can therefore be detected in nanogram to microgram levels in municipal wastewater treatment plants.
Di-methyl-phenol (DMP)
DMP is one of many Xylenol isomers and is used as an active ingredient in multiple industries and manufacturing processes such as synthesis of insecticides, rubbers, dye stuffs and plastics. In high concentrations it presents a an environmental health and safety (ESH) risk being corrosive to tissues. It is safe in low concentrations and is also used as flavoring agents. Due to its wide usage across many industries, it is a common residual by-product in industrial grade effluents as a waste product from manufacturing and needs to be managed in a sustainable way.
Tri-methyl-phenol (TMP)
While there are numerous phenolic compounds, TMP is one of the most abundant in industrial use. Its uses comprise being an active ingredient in the production of Vitamin E, a perfuming agent in cosmetics (partly due to its aromatic structure) and, just like DMP, as a flavoring agent.
In the dying industry, TMP can be used as a potent cleaning agent. Depending on the application, manufacturing process and the concentrations used, TMP is only one of hundreds of phenolic derivatives which can be found in industrial wastewater streams or as a contaminant in clean water processes inside the manufacturing. These compounds must be neutralized with effective purification methods.
Phenols in industrial effluent and emissions
In light of the wide global use of phenolic compounds, the emissions generated from the manufacturing processes are potentially two-fold: wastewater effluent with trace amounts on phenols in ug to mg levels and air exhaust emissions due the volatile properties as Volatile Organic Compounds (VOC). Please see our dedicated information page to treat VOC emissions.
Di-methyl-phenol (DMP) or Xylenol. Common by-product in petrochemical production in the oil & gas industry.
Tri-methyl-phenol. Used in electronics manufacturing such as circuits boards, automobile components and television parts.
Did you know...
…that the global production of phenol was more than 11 million tonnes in 2022 and that a large fraction of that will end up in the environment?
…that the production of phenol is projected to increase by 23% by the year 2030?
…that phenol is used to make nylon clothing?
…that phenol is a key ingredient to extracting DNA at forensic laboratories?
…that luckily Mellifiq can design a solution which will eliminate more than 99% of phenolic compounds before they are released into our air and waters?
Phenols can be treated completely at low operational costs
Despite the significant amount of phenol production globally and its related environmental challenges, the potential to treat phenols is accessible. The molecular structure of phenolic compounds open for a wide array of treatment methods.
Ozonation
Due the aromatic properties of all phenolic compounds, phenol and their derivatives are normally susceptible to oxidation given the double covalent bonds and the asymmetry generated from -OH and/or methyl groups bound to the aromatic structures. Such structures disrupt the molecular resonance present in aromatic compounds. As such, oxidation technologies including ozonation present themselves as viable treatment methods. In addition, given the fact that phenols are present as trace contaminants, the potential to reach near zero levels are realistic. Phenol break-down kinetics are of 1st or 2nd order with ozonation, meaning that up to 95-99% of the phenol concentrations can reduced efficiently.
Mellifiq technicians installing an ozone solution to treat phenols for the process industry,
Advanced oxidation augments the phenol removal rates
As with most process-designs to solve challenging effluent streams, a multi-stage solution is preferred. One such solution is Advanced Oxidation (AOP), in which an oxidation system can be enhanced to further improve the reaction rates and lower the phenol effluent levels further. An AOP may utilize an Ozonetech ozone system combined with Saniray Zeeron UV systems or chemical dosing to produce hydroxyl radicals. Alternatively, Ozonetech RENA Vitro AOP systems with catalytic media can be applied.
Adsorption to capture phenols
Depending on the general characteristics of the effluent water containing phenolic compounds, adsorption with Mellifiq’s WaterMaid FlexKarb-C systems may be a straight-forward option to remove the bulk concentrations. It should be emphasized that the removal levels are strongly dependent on linear flow velocities and retention times applied. Mellifiq wants to be the go-to partner in the optimal design of such systems, employing a careful consideration to the local conditions and the types of phenolic compound to be targeted. We will always tailor a solution with specific adsorption media to optimize the results. Ultimately, the use of a customer-oriented reciprical methods to recommend multi-stage solutions versus single-technology approaches.
Related reference project.
Mellifiq assists Finnish silicon wafer manufacturer in complying with strict wastewater regulations
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