Bridging the waste-treatment gap

Dr. Neil Canter, Contributing Editor | TLT Tech Beat October 2009

A polymeric material is available that removes oil and hydrocarbon droplets between 0.1 and 15 microns.

KEY CONCEPTS
• No techniques have been available to remove oil and hydrocarbon droplets with sizes ranging between 0.1 micron and 15 microns.
• A new polymeric technology known as a Hydrocarbon Removal Matrix incorporates oil droplets in the 0.1 micron to 15 microns range into a polymeric material. The effectiveness rate for this technology is over 99-plus% after one pass.
• The Hydrocarbon Removal Matrix also removes oil and oil-soluble components from most aqueous fluids including emulsions.

Process wastewater generated by manufacturing facilities needs to be treated prior to discharge in order to meet local, state and federal requirements. If the waste is discharged through a sewer system, then one of the main challenges is ensuring that the wastewater does not interfere with the operation of the municipality's Publicly Operated Treatment Works (POTW). A secondary challenge is to process wastewater treatment on-site or recycle the water where it is either less available or very costly to obtain.

Key pollutants that can cause difficulties in treatment of effluent are mineral oil, fatty oils and other oil-soluble organic compounds. These compounds are collectively designated as fats, oils and greases (FOG) and are known to cause difficulties in plugging up sewer pipes and in the operation of POTWs. These same substances will damage membrane treatment systems if these are contemplated for on-site treatment or water recycle.

There are a number of techniques available to remove mineral oil and oil-soluble organic compounds from effluent streams. High concentrations of oils can be removed through conventional techniques such as centrifuges, coalescers and skimmers. This accounts for oils with droplet sizes above 15 microns.

In most process waste-treatment systems, high concentrations of particulates and oils are removed in this fashion, however, sufficient oil and hydrocarbon organic compounds remain at levels causing either POTW permit violations or plugging and high-pressure buildup across the membrane process equipment.

Paul Greco, senior vice president of business development for MyCelx® Technologies Corp., Gainesville, Ga., says, "A gap is present between those techniques that remove large concentrations of oil in the effluent (as large droplets) and those that remove very small droplets. This gap covers oil particles with sizes between 0. 1 micron and 15 microns."

A technique that can bridge this gap by removing oil and hydrocarbon organic compounds from process wastewater effluent would be welcomed to ensure that effluent meets POTW guidelines or that effluent will not damage membrane processes in-use or contemplated for recycle.

HYDROCARBON REMOVAL MATRIX
The challenge of process wastewater treatment within this treatment gap is breaking the oil-surfactant-water bonds that exit. Greco says, "We have developed a polymeric material that can change the properties of hydrocarbons upon contact. Oil is literally incorporated into this polymeric material, which we have designated as a Hydrocarbon Removal Matrix."

The polymeric material is designed to extract oil droplets in the 0.1 to 15 micron range that could not be removed by any other techniques. In addition, the Hydrocarbon Removal Matrix is used in some cases to economically remove oil with a droplet size above 15 microns.

The polymeric material reacts with oil and oily hydrocarbons in less than one second. This high reaction time does not differentiate droplet size but permits capture in a very small treatment footprint. Greco adds, "The Hydrocarbon Removal Matrix traps oils predominantly, but it also can remove hydrocarbons that are soluble in oil or slightly soluble in water. Compounds such as polychlorinated biphenyls, trichloroethylene and methyl tert-butyl ether (MTBE) are representative of these."

The Hydrocarbon Removal Matrix has an effectiveness of more than 99-plus% in extracting insoluble oils from an effluent stream after one pass, according to Greco. Compounds with higher water solubility may require two passes.

A major benefit of the Hydrocarbon Removal Matrix is its ability to extract oil and oil-soluble components from most aqueous fluids. It provides a robust, efficient, cost-effective and operationally simple method of removal that can reduce the cost of an overall treatment process.

Highly stable emulsions cannot be treated as readily if they have low oil droplet sizes. Greco says, "Oil in emulsions with droplet sizes below 0.1 micron cannot be removed." This represents emulsions with very fine droplet sizes that are even smaller than most microemulsions.

Greco says, "Our technology has been used successfully to remove oil from the waste stream of many industrial plants. A recent example involves a glass plant that has a wastewater stream containing a percussion air-tool oil, a polyalphaolefin (PAO)-based gear oil and a vegetable oil. The effluent contains a high concentration of dirt particles and free and emulsified oils. Less than 1 ppm of oil remains in the effluent after a five-stage process is used to remove dirt particles and the oils." 

Once the effluent stream passes through the polymeric material, it can be directly discharged. Figure 3 shows an image of the effluent prior to treatment in the beaker on the left. After one pass through, the clearer effluent is seen in the jar on the right. Greco indicates that ultimately the glass plant would like to recycle the used water.


Figure 3. The polymeric material known as the Hydrocarbon Removal Matrix can efficiently remove oil from wastewater effluent streams with droplet sizes between 0.1 micron and 15 microns. The beaker on the left shows the effluent from a glass plant prior to treatment. The clearer effluent after one pass through is seen in the jar on the right. (Courtesy of MyCelx® Technologies Corp.)

The Hydrocarbon Removal Matrix is provided in cartridges that can be easily replaced. Saturation of the polymeric material is detected when oil is seen in the effluent via oil content monitors or moves through the process cartridges to a visual indicator cartridge. Greco says, "Saturation of the Hydrocarbon Removal Matrix is a function of the viscosity of the oil. As the viscosity drops, the saturation point also declines."

In general, this means that a decrease in viscosity can reduce the amount of oil removed by a 10-inch segment of the polymeric material from 300 to 400 grams down to 100-200 grams. The spent polymeric material can be disposed of in a similar fashion as mineral oil-based hydraulic fluid.

Further information on the Hydrocarbon Removal Matrix can be found at www.mycelx.com or by contacting Greco at greco@mycelx.com. 

Neil Canter heads his own consulting company, Chemical Solutions, in Willow Grove, Pa. Ideas for Tech Beat items can be sent to him at neilcanter@comcast.net.