Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Destruction of hazardous or toxic waste
Patent
1995-02-15
1997-04-15
Pratt, Helen
Chemistry: molecular biology and microbiology
Process of utilizing an enzyme or micro-organism to destroy...
Destruction of hazardous or toxic waste
4352625, B09B 300, B09C 110
Patent
active
056208936
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The changing of the quality of water in lakes and rivers from clear and pristine to murky, green and foul smelling is a natural process called eutrophication. Unfortunately, man's activities have speeded up this process to such an astonishing rate that the changes which would naturally take thousands of years are now noticeable in a matter of a few years and even months. These trophic changes are triggered by the introduction of large quantities of nutrients such as phosphorus and sulfur into the aquatic environments which radically alters the ratio of these elements with the natural systems that have kept them in check.
As nutrients, phosphorus and sulfur promote the growth of a large group of aquatic organisms such as algae as well as many of the higher plants. The threshold level of these nutrients which can trigger this rapid growth appears to be very low, 30 parts per billion (ppb) or less. Oligotrophic, or clear, clean lakes have nutrient values below these levels, whereas, hyper-eutrophic ponds and lakes can have values above 350 ppb. and are characterized by algae, plant growth and, in many cases, the rotten egg smell of hydrogen sulfide.
The use of algicides and aquatic herbicides to control rampant plant populations in lakes is at best an expensive band-aid which must be repeated, several times per year in many cases. Other nutrient controls, such as alum, are extremely expensive, technically demanding and have long term side effects. Unfortunately, it is not merely enough to stop the introduction of new nutrient loads into these environments since the existing nutrients are continually recycled as plants die and decay.
In addition to the changes in trophic state the impact of toxic heavy metals from a variety of sources has left many aquatic environments hazardous to all living systems.
This invention in one aspect relates to methods for controlling sulfur phosphorus and heavy metals in aqueous/sedimentary systems by aquatic nutrient binding and precipitation. Phosphorus as phosphate and sulfur as sulfide are removed by iron binding and precipitation. Heavy metals are removed by replacement reactions in aqueous carbonaceous systems which supress the heavy metal solubility and migration, thus restricting the heavy metal bioavailability. More particularly, in this aspect, the present invention involves methods for controlling excessive epiliminetic bioavailability of sulfur ions and phosphorus ions in aquatic/sedimentary environments such as lakes, ponds and waste treatment systems. Such ions are considered to be "nutrients" in aqueous environments with respect to vegetation, algae and the like. It also controls heavy metals including Hg, Pb, Cu, Ni, Zn, Cr and Mn by direct replacement and precipitation of these less active metals. While particularly focusing upon aquatic environments, the methods of this invention in this aspect are likely to be useful in essentially any aqueous/sedimentary system where control, usually reduction, of the concentration of phosphorus or sulfur ions, among other things, in all of their various oxidation states is desired.
Excessive quantities of sulfur and phosphorus compounds are becoming more prevalent in the environment. These elements are byproducts of many activities which enhance quality of life. Many biological processes also generate these ions, in free or combined form. Excessive concentrations of these elements in the free or combined states in aquatic systems tend to create problems including the aforementioned aquatic eutrophication, objectionable odors and environmental toxins.
Elemental sulfur (that is, sulfur with an oxidation state of zero, S.sup.0) can exist in both oxygenated (aerobic) and deoxygenated (anaerobic) aqueous or aquatic environments. Elemental sulfur also can be activated by oxidation (e.g., in aerobic environments) to sulfate (SO.sub.4.sup.-2) ions; and by reduction to sulfide ions (S.sup.-2). Sulfur in all oxidation states can be utilized to form organic sulfur compounds. Organic sulfur compounds are impo
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Hogen Delman R.
Robin James R.
Hogen Delman R.
Pratt Helen
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