Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2000-09-30
2002-03-26
Simmons, David A. (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S620000, C210S621000, C210S639000, C210S195200, C210S202000, C210S220000, C210S259000, C210S359000
Reexamination Certificate
active
06361695
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a wastewater treatment system and more particularly it relates to a shipboard wastewater treatment system where the system operates in the extreme from very high loading to very low or no loading and may remain in a dormant state for periods of time. Also, the system is useful for treating bilge water.
Treatment of black water (sewage) and gray water (wastewater from showers, sinks, kitchens, etc.) aboard ships has many problems when compared to land-based facilities. For example, onboard ship, low flush vacuum toilets are used for conveying black water and thus there is a lack of water dilution because of the low flush and also because of the absence of surface run-off to dilute the organic load. Further, a variety of devices may be used on board ship to restrict the quantity of gray and black water. All of these considerations result in a wastewater which has an average strength much greater than domestic sewage and a quantity per capita per day which is much lower.
Another problem with onboard ship treatment of wastewater results from the short time between human activity, resulting in waste generation, and arrival of waste at the treatment plant. This results in sharp diurnal variations in waste generation onboard ship in which peak waste quantity and quality tend to coincide rather than being separated as on land. For example, onboard ship, nighttime flow rates may be only one tenth ({fraction (1/10)}) or 10% of the average daytime flow rate, resulting in further problems for a treatment facility.
In addition, onboard ship treatment facilities have a problem with the space that can be dedicated to waste treatment. For example, the height between decks is limited to 8 feet or less, thus standard items for land use facilities cannot be used. Further, ship motion greatly reduces from consideration other standard features, and the lack of trained waste treatment personnel on board requires a very reliable system which is substantially fully automated.
Also, it is important that a system used for black water or gray water be capable of treating bilge water containing oily substances, for example, petroleum and biodegradable material. Thus, by the term wastewater as used herein is meant to include bilge water.
Thus, it will be seen that there is a great need for a shipboard or compact waste treatment system which will overcome these problems and which can be fully automated for shipboard use. Further, the shipboard system must be capable of periods of standby or inactivity, for example, when the ship is in port and yet, be capable of reaching full capacity within a few hours, when the ship is fully loaded with personnel.
Different systems have been proposed for treatment on onboard ship systems. For example, U.S. Pat. No. 5,807,485 discloses an apparatus and method for the continuous biological treatment of ship bilge water contaminated with petroleum and biodegradable materials. The apparatus includes a pumping system attached directly to the bilge or to an oil-water phase separator, for removing the biodegradable material(s) contained in the bilge waste aqueous phase, which is integrated with a means for microbiologically treating the contaminated bilge water. The means for microbiologically treating the contaminated bilge water preferably includes petroleum- and hazardous-degrading microorganisms. In operation, a phase separator system on the ship separates the free-product phase from the contaminated bilge water. The separated free-product is removed for off-site disposal. Contaminated bilge water is fed into the microbiological treatment system for further treatment with eventual discharge overboard or recirculation into the contaminated bilge area.
U.S. Pat. No. 5,151,187 discloses a system for biodegrading oxidizable organic waste in a bioreactor in combination with a membrane ultrafiltration unit used to separate a high quality permeate from activated sludge which is returned to the bioreactor from the membrane unit as a recycle stream. It has been found that in-line fine bubble diffuser or “micronizer” takes advantage of the kinetic energy in the recycle stream to aerate the biomass with surprising efficiency. The micronizer is positioned external to the biomass in the bioreactor; the discharge from the micronizer provides a microaerated tail-jet of the recycle stream which has been infused with a mass of air bubbles from 1-1000 &mgr;m in diameter. The velocity of the compressed air flowed into the micronizer keeps its pores from clogging with sludge. The energy of the recycle stream without the air is insufficient to provide the requisite motive force for adequate oxygen transfer and to establish a predetermined recirculation pattern.
U.S. Pat. No. 5,248,424 discloses a membrane device for withdrawing permeate from a substrate, the flux through the membranes reaching an essentially constant relatively high value because of the critical deployment of fibers of the array as a skein, arching in a buoyantly swayable generally parabolic configuration within the substrate, above at least one of the array's headers in which the terminal end portions of the fibers are potted. The length of each fiber must be greater than the direct center-to-center distance between the array's pair of headers. For use in a large reservoir, an assembly of the array and a gas distributor means has fibers preferably >0.5 meter long, which together provide a surface area >10 m
2
. The terminal end portions of fibers in each header are substantially free from fiber-to-fiber contact.
U.S. Pat. No. 3,472,765 discloses techniques of carrying out biological reactions in conjunction with selectively pressure driven permeable membranes to effect high rate separation of biological life from a carrier liquid or a valuable product of the reaction.
U.S. Pat. No. 4,749,494 discloses an activated sludge treatment process for waste water. In the waste water treatment, waste water containing organic matter is introduced into an activated sludge reaction tank. The excess sludge formed in the reaction tank is introduced into a sludge digestion tank to effect the digestion of said excess sludge by intermittent aeration with air. A part of the digestion tank liquid is passed through a filtration apparatus having an ultrafiltration membrane. The filtrate passed therethrough is withdrawn outside the system and the remainder is circulated to the digestion tank to maintain the liquid volume of the digestion tank at a definite level. When the amount of the reaction tank liquid introduced from the reaction tank into the digestion tank is taken as W
1
, the digestion tank liquid is returned in an amount of (0.2-0.8) W
1
to the reaction tank. Thus, the amount of excess sludge to be treated outside the system can be reduced or can be completely eliminated.
U.S. Pat. No. 5,254,253 discloses a system for treating oil water or bilge water in addition to treatment of black water and gray water. The combination provided the essential nutrients for a mass of mixed microorganisms which are well adapted to ingest the nutrients. To facilitate availability of oxygen to the microorganisms so as to provide growth of the microorganisms, and also, to allow them to destroy themselves, excess oxygen is discharged, in a combination of microbubbles and macrobubbles, into a membrane bioreactor (MBR). The mixture of bubbles is preferably generated with coarse (>2 mm) and fine (<20 &mgr;m) bubble diffusers. An auxiliary stream, whether alone or a recirculating stream into which air is drawn, may provide the coarse bubbles. The air is entrained in a jet aerator or eductor in a recirculating loop of activated sludge taken from the MBR. Another portion of the contents of the MBR is pumped to a semipermeable membrane which provides water (permeate) of excellent quality. The remaining concentrate is led to a gas micronizing means which produces a tail-jet of microaerated concentrate. The tail-jet is returned to the MBR to provide kinetic energy for maintaining a high veloc
Behmann Henry
Husain Hidayat
Liu Ming Gang
Tonelli Fernando A.
Alexander Andrew
Prince Fred
Simmons David A.
Zenon Environmental Inc.
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