Liquid purification or separation – With gas-liquid surface contact means
Reexamination Certificate
2000-03-22
2001-08-21
Upton, Christopher (Department: 1724)
Liquid purification or separation
With gas-liquid surface contact means
C210S170050, C210S262000, C210S602000, C210S903000
Reexamination Certificate
active
06277274
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is a system, method, and apparatus to improve the quality of stormwater runoff or sanitary wastewater effluent by removing pollutants, and, more particularly to a system whereby contaminated water is passed through a one or two-stage complex high flow rate mixed media treatment system. The first stage treatment uses mulch, soil particles, microbes and live plants to treat contaminated water where it flows by gravity to the second stage where pollutants are further removed by sedimentation and anaerobic microbiological processes. Under certain conditions, only the first stage treatment may be effectively utilized.
2. Background Information
Land development results in an increased stormwater runoff. The increased runoff can be as much as 5 to 10 times higher compared to pre-development conditions. This increased runoff can carry with it a variety of pollutants generated from diffuse sources. The pollutants can include sediment from construction sites and stream erosion, heavy metals, oil and grease, toxic organic and inorganic chemicals, nutrients and organic materials depending on the land use. One objective of current stormwater management programs is to remove these pollutants from the runoff prior to it being discharged to surface waters or percolating into the ground water. There are a variety of so-called “best management practices” (BMP's) which are used to remove pollutants. Some of these include retention and detention ponds, wetlands, forested buffers, sedimentation basins, infiltration trenches, grass swales, and various types of filters using peat, sand, soil and leaf mulch and aggregates.
The enactment of the 1972 Clean Water Act (CWA) (and subsequent amendments) recognized the adverse environmental impacts of point and nonpoint pollution on the physical, chemical and biological integrity of our receiving waters. Since enactment of the CWA and the subsequent implementation of National Pollutant Discharge Elimination Systems (NPDES) permit program industries, states and local governments have been in the process of developing strategies and technologies to reduce both point and nonpoint pollution problems. Nonpoint source pollution is the term used to describe the diffuse and non-discrete sources and character of the pollution that can contaminate stormwater runoff. As stormwater runoff flows across the surface of developed land, it can become contaminated with and transport such pollutants as sediment, nitrogen, phosphorus, bacteria, heavy metals, insecticides, pesticides, herbicides, trash, debris, organic material and petroleum products. There is no one source of this nonpoint pollution. Instead this pollution comes from many sources associated with changes in land use, human activities and air pollution deposition. Point source pollution emanates from discrete easily identifiable discharges such as a pipe discharging effluent from wastewater treatment plant, factory or septic system.
High levels of point or nonpoint pollutants in surface waters will result in the degradation of the water quality to receiving surface waters (streams, rivers, lakes and reservoirs), contamination of ground water supplies as pollutant laden waters percolate in the ground and destruction of the aquatic biota (plants, fisheries and invertebrates) sensitive to poor water quality. Contaminated runoff can have a deleterious effect on the human health by degrading the quality of drinking water supplies.
Since the early 1980's regulations have been in place requiring new development to reduce problems associated with nonpoint pollution and stormwater runoff. Numerous BMP's have been developed to treat stormwater to capture, remove or transform pollutants thus reducing their levels in the discharge to surface waters.
The character and levels of the major constituents polluting stormwater runoff are well known and have been studied for many years. The first program to characterize pollutants and their levels in runoff was performed by the United States Environmental Protection Agency (EPA) in a multi year Nationwide Urban Runoff Program (NURP) which began in 1979. They studied 28 separate urban areas across the nation. For example, in the Washington, D.C. metropolitan area the EPA studied urban runoff over a four-year period from 1979 to 1983, and the results were published in 1983 (PO-003208-01). Table 1 summarizes some of the pollutant level contamination findings of the Washington, D.C. area study. The concentrations shown are the averages of all samples examined during the study period.
TABLE 1
Average
Constituent
Concentration
Comments
Sediment
80 ppm
Max levels up to 500-600 ppm
affects water clarity
Total Phosphorus
03. ppm
Stimulates algae growth
Total Nitrogen
2.1 ppm
Stimulates algae growth
Chemical Oxygen
40 ppm
Indicator of high organic content
Demand
Bacteria
200 to 240,000
Indicator of possible pathogens in
MPN/l
water
Zinc
60 ppb
Toxic to aquatic organisms
Copper
5 ppb
Toxic to aquatic organisms
Nickel
30 ppb
Product of fossil fuel
Lead
15 ppb
Toxic to aquatic organisms
Pesticides
<0.1 ppb
Garden pest Control
Phenols
<10 ppb
Leaches from stains
Assorted Organic
<10 ppb
Compounds
Notes: ppm = parts per million or milligrams per liter (mg/l)
ppb = parts per billion or micrograms per liter (ug/l)
The study concluded that the pollutant levels in urban runoff represent a significant threat to the integrity of receiving waters. The high sediment loads cause excess turbidity blocking light to submerged aquatic plants. High phosphorus and nitrogen levels (nutrients for plant growth) cause excessive algae growth, which depletes the water of oxygen suffocating fish and other organisms. Bacteria levels were above public health criteria for recreational activities.
The benefit of filtering contaminated water (stormwater or wastewater) through or bringing it into contact with such constituents as soils, sand, silts, clays, organic material, microbes and plants to treat and remove pollutants from stormwater runoff and wastewater is well known. A variety of complex multimedia filters have been used in the past to remove contaminates from drinking water, wastewater and stormwater runoff. These would include grass swales, stormwater management ponds, wetlands, land spray irrigation treatment systems for wastewater, naturally vegetative buffers, sand filters and bioretention systems.
Constructed ponds incorporating shallow wetlands systems are an example of a BMP that uses a variety of physical, chemical and biological processes to treat stormwater runoff. Runoff flows through the stormwater pond where sedimentation occurs removing particles from the water column and associated pollutant such as organic materials and heavy metals attached to the particles. Runoff is exposed to the pond soils where pollutants are capture by adsorption onto organic and inorganic constituents of the soil. Biological processes occur in the water column by bacteria, algae and plants that assimilate, transform and uptake pollutants and nutrients as part of their metabolic processes. Ponds require long detention times to remove suspended particulate matter due to the time it takes for very small particles to settle out of the water column. Varying intensities of rainstorm events can cause high flow rates through the ponds reducing the time for treatment and poor designs that shorten retention times cause the pollutant removal rate of ponds to be highly variable. High storm flows can cause re-suspension of particles thus flushing out captured pollutants. Under high flow and poor design conditions, ponds have been shown to export some pollutants associated with the re-suspended soil particles.
For BMP's such as ponds, swales and forested buffers, plants play an important role in the removal of various pollutants as they can assimilate into their tissues and incorporate into their bio-mass many of the pollutants or by-products of the break down of the pollutants accomplished by microbial
Jacobson & Holman PLLC
Upton Christopher
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