Oil Sorption Properties of X-TEX vs. Polypropylene for Storm Water Catch Basin Inserts

Introduction - Both industry and municipalities are increasingly utilizing storm water basin inserts as a best management practice (BMP) control for storm water runoff pollution control. The inserts are closest to “point of origin” and in many cases the only line of defense for protecting our waterways from secondary pollution sources. The storm water inserts used today are devices that are installed into catch basins to help reduce pollutants that are washed off automobile parking lots, roadways, etc. These inserts must be strong enough to withstand the physical abuse of the environment and the introduction of up to several pounds of sediment (1). The oil adsorption capabilities and physical properties of the inserts must not significantly degrade for many months after installation to insure limited maintenance and assure cost effectiveness.

Most catch basin inserts in use today are constructed of “virgin” polypropylene material, which has an oil and grease removal efficiency of 78 to 87 percent (2,3). No “recycled” adsorptive material was found that had the same or better adsorbent abilities and physical properties as polypropylene based materials…..until now.  Now a new textile has been successfully developed from a blended bulk fiber media derived from “recycled polymeric waste”. This textile “blanket” has superior oil adsorption and absorption, physical attributes that withstand the rigors of the environment and is cost effective. The textile blanket and blended fiber material are registered under the trade name Xextex (patent pending). X-TEX gives engineers, designers and manufactures an innovative recycled material for their storm water inserts. X-TEX is currently being used successfully in storm water filtering systems for the removal of free oil and grease, and many types of emulsified oils as found on construction sites and in truck washing facilities.

The following tests compares the oil and grease adsorption properties and capacity of polypropylene 225EX material and the X-TEX blanket material. Both materials are similar in weight per volume basis. An equal size and weight of each material was used.


Method - A test apparatus was designed to evaluate the insert performance and absorbance/adsorbance of X-TEX and polypropylene. A 9 by 12 inch drain frame was assembled using heavy plastic strips. Each test material was cut into a 14 by 18 inch rectangle that allowed for a 4-inch deep pocket to be formed for the introduction of the effluent oil stream. The insert material was clamped between the plastic frame and PVC pipe was used to deliver a constant water flow of 10 liters per minute. The end section of the pipe was perforated to allow even distribution of water over the entire length of the test area pocket.

A mixture of 50 percent used motor oil and 50 percent diesel was injected into the PVC delivery pipe using a metering pump. The oil was metered into the influent stream at one gram per minute, and the flow rate was held constant at 10 liters per minute, yielding a 100 mg/l influent waste stream. Although this concentration is much higher than actual environmental field conditions, the amount of oil effluent was sufficient to measure a break-through point of each material.

The two materials were tested at both a single and a double thickness at high concentrations to determine if additional removal efficiencies could be improved by using more material. Each material tested was exposed to a total of a 10-minute flow of oil/water effluent. Samples were collected at 1,2,4,6,8 and 10 minute intervals of filtering. A total of 10 grams of oil was discharged with 100 liters of water for each test. The oil/water effluent passed through both materials for all tests without collecting or pooling. Samples were analyzed using EPA 418.1 method for total petroleum hydrocarbons.


Results -  The results from this bench test demonstrate that the X-TEX blanket out performs the polypropylene material substantially for the single layer and double layers of material.
For the single layer the polypropylene break-through of the effluent occurred just after two minutes of testing with a drop from 84% to 64% removal rate. The X-TEX material maintained a high percent of removal until break-through between the 9th and 10th minutes of the test when the removal rate dropped from 85 % to 69 %. There was no break through for the two layered X-TEX material or the polypropylene textile under the test conditions. Table 1 summarizes these results, and Graph 1 shows these test results in percentages. 


Diesel / Motor Oil Removal from Water – Polypropylene Textile vs. X-TEX Blanket

Table 1

Amount of Diesel/Oil Added

Amount of Diesel/Oil Removed (ppm)

Amount of Diesel/Oil Removed (percent)

Time (min)

Total (grams)

Oil/Water (ppm)

PPL Insert

X-TEX

PPL Insert

X-TEX

1 0.88 88 65 87 74 99
2 1.76 88 74 87 84 99
4 3.52 88 56 86 64 97
6 5.28 88 31 75 36 85
8 7.04 88 20 75 23 85
10 8.8 88 17 61 20 70
Graph 1- Percent of removal for single layer test

Chart - Xextex vs Polypropylene


Conclusions - The test data illustrates that the polypropylene textile material initially retains about 80% of the oil/diesel blend while the X-TEX blanket retains virtually 100% of the oil from the influent waste stream. With a 10-gram total oil influent load, the polypropylene textile removed 6.0 grams of oil and allowed 4.0 grams of oil into the effluent stream, resulting in a 60% oil removal rate for the entire test. The X-TEX blanket removed 9.0 grams and allowed 1.0 gram of oil to pass through removing 90% of the total oil.

Oil breakthrough / saturation for the polypropylene textile occurred after 2 grams of oil/diesel had been retained. For the X-TEX blanket the breakthrough / saturation point was after 8 grams of oil retention, indicating an oil retention capacity four times greater.

The actual adsorption area was restricted to a 4 x 8 cm. area representing the effluent flow at the low point of the insert pouch. This effluent point will shift as sediment excludes exit sites in real-world inserts, and the oil adsorption capacity will extend to the entire insert surface area, greatly increasing the inserts total capacity. The oil/diesel influent concentrations used in these tests were intentionally high and were meant to determine an insert materials capacity, not simulate real world conditions.

Test Conducted by: Brent Hepner, Vice President and Director of Product Development, The Xextex Corporation USA, Assisted by Tom Coyner Technical Director for Product Design, The Xextex Corporation USA.


Acknowledgements - Thanks go to Planet CPR and Mark Shaw of Ultratech for their help both technically and with their assistance in supplying us with catch basin insert material for our comparison tests.

References
1. M.E.Hrachovec, P.E., and G.R.Minton, PhD., P.E. (2001), “Field Testing of a Sock-Type Catch Basin Insert”.
2. M.E.Hrachovec, P.E., and G.R.Minton, Phd., P.E. (2001), “Bench Testing of a Sock-Type Catch Basin Insert for Removal of Free Petroleum”.
3. M.K. Stenstrom, S.L Lau, and E.Khan (1998). “Catch Basin Inserts to Reduce Pollution From Stormwater”.

 

The Xextex Corporation, USA


Jerry M. Brownstein
President & CEO
1420 NW Gilman Blvd. #2227
Issaquah, WA 98027

Phone: (425) 392.3848
Fax: (425) 392.0222
Email: jbxextex@comcast.net


VIDEOS:

X-TEX DEMONSTRATION
90 SEC

OIL BOOMS:
X-TEX Outperforms Polypropylene

YouTube

Ultra-X-Tex
Demonstration

YouTube
*X-TEX does not produce
potable water.

VMS UTILITY VAULT DEWATERING TRAINING FILM
10.5 MIN