WE NOW HAVE OUR OFFICIAL PATENT!

IN SITU TREATMENT OF STORM WATER

Presented at the Central States Water Environment Annual Meeting - Rochester, Minnesota
May 20, 1999 - Nonpoint / Watershed Session
Harry Jebens*, PE, PhD, DEE and Lyle Clemenson**

INTRODUCTION

The treatment of storm water and snow melt runoff has been attempted by different classes of systems: storm water retention ponds, end of pipe systems, and inlet treatment devices. Each system has its own inherent advantages and applications. The patented Raynfiltr® developed by Environmental Filtration, Inc. of Brooklyn Park, Minnesota is an inlet treatment device. The system was developed as an outgrowth of a need recognized in 1993 by Lyle Clemenson, president of Environmental Filtration, who was serving as Chair of a Blue Ribbon Task Force on Storm Water / Land Use. The Task Force was appointed by the then Mayor of Brooklyn Park, Jesse Ventura.

THE Raynfiltr®

The Raynfiltr® utilizes a canister that is 20 inches in diameter and 36 inches in height that is placed in inlet basins to remove pollutants from storm water and snowmelt runoff. The canisters have a removable cone shaped inlet screen to remove large particulates. The lower portion of the inlet screen has a porous material that removes fine particulates. The canisters also have a similar exit cone that prevent blockage of the canister by fines or precipitates. Figure 1 shows the components of a Raynfiltr® in a catch basin.

Figure 1 Raynfiltr® Canister

The Raynfiltr® Media is a peat derivative. The process to produce the media begins with mixing raw peat with a sulfonating agent - this enhances the natural ion exchange capacity of peat to remove heavy metals. The next step in the process is to dewater the mixture - initially by gravity and then utilizing a press. Next a binder is mixed with the sulfonated peat. The mixture is then extruded to form pellets. The pellets then flow through a rotary kiln at very high temperatures and in the absence of oxygen - this gives the media the additional characteristics of Activated Carbon. Figure 2 is the process schematic for producing Raynfiltr® Media.

Figure 2 Process to Produce Raynfiltr® Media

INSTALLATION

The canisters can be easily installed in existing catch basins where surface runoff represents an environmental hazard - upstream of lakes, ponds, and groundwater recharge basins. Maintenance is easy - simply remove the inlet grate and remove the inlet cone. The solids removed by the inlet prefilter and cone can be disposed of via landfill with municipal refuge - they are not a disposal problem.

HYDRAULIC CAPACITY

The Raynfiltr®inlet cone has a porous fabric that acts as a prefilter to remove fines, The prefilter occupies the lower portion of the inlet cone. The large size of the media allows high flow rates through the system. The hydraulic capacity of the units using graded media is 0.8 cfs ~ 350 gpm (22 l/sec), When runoff flows exceed this amount the excess flows out of the canister through the High Flow Orifices (36 2" Diameter Orifices surrounding the canister). Even at inlet flows up to 3.0 cfs the runoff will pass through the Inlet Screen. Most storm water inlets are over designed. Inlets with curb openings allow larger particulates to enter the systems (kids balls and beverage containers). When inlets appear to back up the cause can usually be traced to downstream water levels not inlet grate capacity.

PROCESS OF CONTAMINANT REMOVAL

Contaminants are removed by physical, chemical, and biological means. The physical removal of particulates begins in the canister inlet cone. A prefilter of high porosity fiber in the lower 8" of the inlet cone serves to filter out fine particulates. When the capacity of the prefilter is exceeded, the excess runoff passes through the upper 2" of the inlet cone and gross particulates are filtered out. In passing through the Raynfiltr®, further removal of particulates takes place.

Chemical removal of contaminants in solution takes place due to the unique nature of the Raynfiltr® media. Removal mechanisms are: adsorption, absorption, chemical fixation, and biological conversion. Due to the high surface area of the Raynfiltr® media rapid removal of contaminants in solution is due to adsorption. Heavy metals in solution are removed via transfer to exchange sites within the media pores and fixation via ion exchange - the exchange ion is Hydrogen. Unlike conventional ion exchange resins, peat based medias are not effected by calcium, magnesium, and sodium in the stream of water being treated. Organics in solution are likewise removed by adsorption onto the surface of the media and absorption into the media. Biological conversion of organics takes place for organics removed onto the media surface and to organics that become trapped within the biological film that develops on the media. Phosphates are removed via chemical fixation with metals retained and removed by the media.. Figure 3 is an attempt to depict the mechanisms for the removal of contaminants by Raynfiltr® media.

Figure 3: Mechanisms of Removal of Contaminants

Raynfiltr® EFFECTIVENESS

Laboratory testing and initial demonstration field testing in Brooklyn Park, Minnesota have yielded promising results. Laboratory testing of pond water resulted in the removal of: Cu from 9.91 to 0.03 mg/l, Cr from 0.06 to 0.02 mg/l, and Pb from 1.69 to 0.02 mg/. Laboratory test on five different hydrocarbons resulted in removals of 74.1 to 88.9%. Field tests on phosphorous removals where initial concentrations ranged for 0.48 to 1.30 mg/l resulted in concentrations of 0.06 to 0.30 mg/l after passing through the Raynfiltr® for removal efficiencies of 70.5 to 87.5%.

SYSTEM COSTS

Cost are $500 per unit which includes media. Media replacement should be performed in the fall and more often in more suspected contaminated locations - inlets where high concentrations of pollutants are expected. Replacement media costs $195 / canister. The Inlet Screens should be inspected periodically visually and cleaned when necessary - typically once in the spring and once in the summer. Environmental Filtration disposes of the spent media.The spent media is graded into three categories: Saturated - this media is crushed, bioactivated and refined into commodity-grade, natural phosphorous based fertilizer and soil conditioner, Recyclable - this media is hydro and pyro-thermally reactivated for use in industrial treatment applications, and Contaminated this media is disposed of by industrial recyclers.

FURTHER STUDIES

Additional work to verify and demonstrate the efficiencies for the removal of contaminants, capacity of the Raynfiltr® media under field conditions is in progress. Research sponsored by Environmental Filtration at Bemidji State University is underway to characterize the media and the mechanism for phosphorous removal. The Beltrami Soil and Water Conservation District has recently applied for a Conservation Partners Grant to the Minnesota DNR - "Enhancement of Aquatic Habitat Through Stormwater Treatment". the University of Minnesota has developed a research proposal to characterize and test our media and are seeking funding from regulatory agencies.

In addition Environmental Filtration, Inc. is in the process of entering a program of verification testing through EPA's partner NSF International.