CA3040777A1 - Method and system for treating water - Google Patents

Description

METHOD AND SYSTEM FOR TREATING WATER
BACKGROUND OF THE INVENTION
1. Field of Invention The present invention relates generally to water treatment and in particular to a method and apparatus for treating contaminated water.

2. Description of Related Art Produced water is one of the major by-products in the process of exploration and production of oil. Its composition may vary, however depending on the process it may include (but is not limited to):
a. Dissolved and dispersed oil compounds;
b. Dissolved formation minerals;
c. Production chemical compounds, d. Production solids (including formation solids, scale and corrosion products, bacteria, waxes, and asphaltenes );
e. Dissolved gases.
The US Geological Survey operates under the estimate of 7 barrels of water for 1 of oil. The Provincial Government of Alberta, Canada, estimates a 3/1 ratio. Given these large quantities of water that are produced by such process, it will be appreciated that an efficient means of cleaning such water for reuse is required.
SUMMARY OF THE INVENTION
According to a first embodiment of the present invention there is disclosed a system for treating water derived from an industrial process comprising removing solid material from said water with a centrifuge and passing said water through a plurality of tanks, each of said plurality of tanks including a plurality of cells in which said water passes sequentially through said plurality of cells in each of said plurality of tanks, wherein at least one of said cells contains a quantity of a dried macrophye biomass.

Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
In drawings which illustrate embodiments of the invention wherein similar characters of reference denote corresponding parts in each view, Figure 1 is a perspective view of an apparatus for treating wastewater according to a first embodiment of the present invention.
Figure 2 is a schematic representation of the system of Figure 1.
Figure 3 is a schematic view of one of the tanks of the system of Figure 1.
Figure 4 is a cross sectional view of one of the cells of the system of Figure 1.
Figure 5 is a schematic illustration of one channel of the stages of the system of Figure 1.
DETAILED DESCRIPTION
Referring to Figure 1, an apparatus and system for treating according to a first embodiment of the invention is shown generally at 10. Although the apparatus 10 is illustrated in Figure 1 as being contained within a frame or skid, as are commonly known for portable use, it will also be appreciated that the system may be utilized as separate elements or installed in arrangement.
In particular, the apparatus 10 comprises a frame 12 housing the elements which comprise the system comprised of a centrifuge 20 and a plurality of tanks 30. As illustrated in Figure 1, the system may comprise first second and third tanks 32, 34 and 36, respectively as will be more fully described below.

Optionally, the system 30 may include a pump 14 adapted to pump the waste water through the remaining components. The system may be formed as a single sequence of the centrifuge 20 and tanks 30 or may optionally have more than one of each element so as to provide redundancy.

-3-With reference to Figure 2, a schematic view of the system 30 is illustrated.
As illustrated in Figure 2, the system 30 may include first and second channels 16 and 18 which each includes a centrifuge 20 and first, second and third tanks 32, 34 and 36. As illustrated, the waste water may enter at an entrance 22 which may be connected to a source of waste water in any manner known and a discharge 24 which discharged the treated water to any desired location and may be connected to any other subsequent systems.
The system 30 includes a pump 14 before each centrifuge 20. The system 30 may optionally include a further pump 14 after each centrifuge and before the tanks. As illustrated in Figure 2, the system may include cross-pipes 26 extending between each channel 16 or 18 and the opposite channel. The cross-pipes 26 may include valves 27 as do each channel 16 or 18 along with pressure 28 gauges. The valves permit the contents of each channel to be mixed with each other as well as to isolate one or more of the tanks for maintenance.
Turning now to Figure 3, a schematic of one of the tanks 30 is illustrated. In particular, the view of the tank 30 is Figure 3 is illustrated as a horizontal cross section. Each tank includes a plurality of cells, 40, 42, 44, 46, 48, 50 and 52 therein. Although the cells are illustrated in Figure 3 as upright, other configurations may also be utilized. As illustrated, the waste water is directed through each of the cells 40 through 52 in sequence. Each of the cells may include a different media so as to remove a different contaminant from the waste water as will be further described below.
As set out above, the system 30 can be organized into 5 steps of removing contaminants from waste water. As illustrated in Figure 5, the schematic of a single channel is illustrated having a centrifuge 20 and first, second and third tanks 32, 34 and 36. The first step is performed by the centrifuge 20 wherein solid wastes 21 are removed for disposal. It will be appreciated that with such removal, the results will be improved by reducing the contamination of the absorbents by the particulate material and in particular the due to the BOD
Biochemical Oxygen Demand and COD Chemical Oxygen Demand

-4-Thereafter, the second and third steps may be performed in the first tank 32.
The second step comprises the removal of oils, greases and other petroleum based contaminants. In the second step, an absorbent plant based material (SORB) is utilized. In particular, in one embodiment of the present invention, the first, second and third cells of the first tank may be utilized for such first step. It will be appreciated that due to the removal of oils and greases by the SORB, that the subsequent filtering is improved due to preventing the subsequent filtration media from becoming contaminated with the oil and grease.
The third step may also be performed in the first tank 32 such as within cells through 7 by way of non-limiting example and consists of removal of phenols and other contaminants. The fourth step may be performed in the second tank 34 and consists of removal of ammonia (NH3) and sodium chloride (NaCI) along with nitrates, nitrites with the use of activated charcoal and sedimentary rock. In step five, all resident residues will be removed by a combination of the SORB, activated charchol and a final filter in the third tank 36. The tank and cell contents are summarized for the above example in the following table.

-5-Table 1: Example of Cell Contents Cell 1 SORB SORB SORB
Cell 2 SORB SORB Activated coal Cell 3 SORB sedimentary rock Reactivated coal and activated coal Cell 4 Activated coal and sedimentary rock Reactivated coal SORB and activated coal Cell 5 - Activated coal sedimentary rock Reactivated coal and activated coal Cell 6 Activated coal and sedimentary rock Reactivated coal SORB and activated coal Cell 7 Activated coal sedimentary rock Filter and activated coal It will be appreciated that depending upon the waste water that the system is to be utilized with, the distribution of steps may be varied in location and size within the tanks and cells.
As set out above, SORB is utilized to remove oils and greases from the waste water. The SORB comprises a natural absorbent element obtained from the crushing and drying processes of the macrophyte biomass. Macrophytes are aquatic plants that live on and/or in any aquatic environments (including fresh and salty water). In the present system, any suitable macrophyte may be used. In particular example of such suitable SORB include, but are not limted to Eichomia crassipes, Pistia stratiotes, Salvinia auriculate e Potamogeton natans. The SORB is prepared by drying the plant material to a dryness of less than 5% water by weight although it will be appreciated that other moisture levels may also be useful as well. After drying the plant materials are then crushed or otherwise reduced in size to meet the requirements for that particular stage of filtration as illustrated below with respect to the third cell 46 of the first tank 32. After the drying process the biomass assumes special characteristics that confer high absorption power (due to its external

-6-capillary structure) and retention (due to its internal cellular structure that is porous).
It also has the characteristic of being hydrophobic, which guarantees sorption only of contaminants that are mixed in the effluents to be treated.
As illustrated in Figure 4, one of the cells 46 of the first tank 32 may be formed with varying levels of a mesh through first, second, third and fourth stages 60, 62, 64 and 66, respectively. Each of the first, second, third and fourth stages 60, 62, 64 and 66 may have different screen opnenings or filtration sizes. In particular the third cell 46 of the first tank may, as set out above, comprise a SORB step wherein the first, second, third and fourth stages 60, 62, 64 and 66 are filled with granular SORB material. By way of non-limiting example, the first stage may be filled with particles of SORB of a mesh 50 size granular size wherein the second stage includes particles of a mesh 8, the third stage having particles of a mesh 1/4" and the fourth stage having particles of a mesh 3/8" as are commonly known. As illustrated, the water enters the cell proximate to a bottom 47 and exits proximate to a top thereof. A transfer pipe 54 then transfers the water to the bottom of the next cell. It will be appreciated that the depth of each cell and stage within that cell will depend upon the particulars of the waste water and the contaminants therein. The level of compaction of each of the stages within the cell may also be varied to ensure that the effluent can flow into the cell.
The present system is designed to increase the efficiency of the treatment of waste water. In particular, such water treatment systems may be useful in particular for use in treating waste water resulting from the petrochemical industry, such as marine loading and unloading terminals, prospecting platforms, oil capture at prospecting of underground wells and oil capture at refineries by way of non-limiting example. In particular, the present system is useful in the retention of oils and greases, as well as phenols, cyanides, sulfides, ammonia, suspended solids and other components from such waste water.

-7-While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the above description.