AU2006207887B2

AU2006207887B2 - Waste water treatment process

Info

Publication number: AU2006207887B2
Application number: AU2006207887A
Authority: AU
Inventors: Malcolm Close
Original assignee: NEATPORT Pty Ltd
Current assignee: NEATPORT Pty Ltd
Priority date: 2005-09-07
Filing date: 2006-09-07
Publication date: 2012-06-14
Anticipated expiration: 2026-09-07
Also published as: AU2006207887A1

Abstract

A process for treating waste water, the process comprising the steps of: (a) collecting the waste water; 5 (b) adding a nutrient dose to the collected waste water; and (c) subjecting the dosed waste water to aerobic digestion. H:\SherylM\Keep\Speci\P62069.doC 7/09/06

Description

AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant: Neatport Pty Ltd Invention Title: WASTE WATER TREATMENT PROCESS The following statement is a full description of this invention, including the best method of performing it known to me/us: -2 WASTE WATER TREATMENT PROCESS Field of the Invention The present invention relates to waste water 5 treatment processes. Background of the Invention Waste water treatment processes involving the aerobic digestion of organic wastes have been previously 10 proposed for waste waters such as raw sewage which contain high levels of bacteria, which although toxic to human consumption are actually used in the aerobic process to breakdown the organic waste. This is achieved by providing the bacteria with oxygen (typically by a source is of air) to enable the bacteria to feed off the organic waste. Summary of the Invention According to a first aspect of the present invention there 20 is provided a process for solely treating grey waste water, the process comprising the steps of: (a) collecting the grey waste water and not any raw sewage; (b) adding a nutrient dose to the collected waste 25 water which is not raw sewage; and (c) subjecting the dosed waste water to aerobic digestion. Preferably, the grey waste water would be unresponsive to step (c) without first performing step 30 (b). Grey water includes waste water from fixtures such as baths, sinks, washing machines, and the like. Preferably, the step of collecting the waste 3330518_1 (GHMatters) P57936.AU.1 2105/12 -3 water occurs in a tank. However, in other embodiments it may be collected in other storage devices such as a pond for example. Preferably, the step of aerobic digestion occurs s in an activated sludge tank. The activated sludge tank may or may not be the same tank in which the waste water is collected. Preferably, the nutrient does comprises a flocculant and at least one of a source of carbon and a source of 10 nitrogen Preferably, the source of carbon is a sugar. Preferably, the sugar is glucose. Preferably, the source of carbon is added to the waste water at 0.1-1.0 grams per litre of waste water, is more preferably 0.3-0.7 grams per litre, even more preferably approximately 0.5 grams per litre. Preferably, the source of nitrogen is a nitrate or urea. Preferably, the source of nitrogen is added to the 20 waste water at 0.1-1.0 grams per litre of waste water, more preferably 0.3-0.7 grams per litre, even more preferably approximately 0.5 grams per litre. Preferably, the flocculant is aluminium sulfate. Preferably, the flocculant is added to the waste 25 water at 0.1- 1.0 grams per litre of waste water, more preferably 0.3-0.7 grams per litre, even more preferably approximately 0.5 grams per litre. According to a second aspect of the present invention, there is provided a nutrient dose for use in a 30 process for treating grey waste water, the nutrient dose comprising at least one of a source of carbon and a source of nitrogen and a flocculant. 3330518_1 (GHMatters) P57936.AU.1 2/05/12 - 3a Preferably, the nutrient dose comprises a mixture of glucose, urea and aluminium sulphate. s Brief Description of the Drawings A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a plant for 3330518_1 (GHMatters) P57936.AU.1 2/05/12 - 4 carrying out the waste water treatment process according to preferred embodiments of the present invention; and Figure 2 is a schematic view of the plant according to Figure 1. 5 Detailed Description of Preferred Embodiments Referring to Figure 1, a waste water treatment plant 10 for carrying out a waste water treatment process according to preferred embodiments of the present 10 invention is shown. The waste water treatment plant 10 comprises an aerobic treatment chamber 11 and an effluent storage tank 12, shown in Figure 1 located inside the aerobic treatment chamber 11 for compactness of the plant 10. The plant also comprises a floating decanter 13 which 15 transfers treated effluent via a chlorinator 14 from the aerobic treatment chamber 11 into the effluent storage chamber 12. The floating decanter 13 operates similarly to the decanter described in the Applicant's own patent AU 674511. 20 The treatment plant 10 further comprises a motor box 15 which drives an air blower 16 for periodically re aerating the waste water in the aerobic treatment chamber 11. An air diffuser 17 at the base of the aerobic treatment chamber 11 distributes the air through the waste 25 water. The waste water treatment plant 10 has an inlet 20 which delivers untreated waste water into the aerobic treatment chamber 11. The waste water delivered to the aerobic treatment chamber 11 enters firstly a stilling 30 well 21 in the treatment chamber 11 in order to prevent the incoming waste water from interfering with the treatment process. In the embodiment shown in Figure 1, the stilling well 21 comprises a baffle 22. The baffle 22 is semi-circular in shape with its curvature opposing that 35 of the facing wall of the aerobic treatment chamber 11. The baffle is slightly spaced away from the wall of the aerobic treatment chamber 11 so the waste water can exit H;\SherylM\Keep\Speci\P62069.doc 7/09/06 - 5 the stilling well 21 around the sides of the baffle 22. In an alternative embodiment (not shown) the stilling well 21 is a stilling tank, located inside the aerobic treatment chamber 11. Waste water enters the 5 stilling tank through the inlet 20 and a pump at the base of the stilling tank pumps water from the bottom of the stilling tank to exit the stilling tank and enter the aerobic treatment chamber 11 towards the top of the stilling tank. 10 The waste water treatment plant 10 also comprises an effluent outlet 25 from the effluent storage tank 12. Treated effluent is delivered to the effluent outlet 25 by a treated effluent pump 26 located at the bottom of the effluent storage tank 12. 15 Typically, the waste water treatment plant 10 is utilised to recycle domestic grey water. In this case the waste water treatment plant 10 is located on or near the domestic property or properties for which it is used, with the inlet 20 to the waste water treatment plant 10 20 connected to the grey water outlet or outlets of the properties and the outlet from the waste water treatment plant 10 connected to the inlet or inlets of those fixtures on the properties that can utilise the treated effluent, such as toilets or sprinkler systems for 25 example. Referring also to Figure 2, the waste water treatment plant 10 also comprises a float control system 29 for operating the effluent storage tank 12, including a control box 30 for processing and executing the signals 30 used in the float control system 29. The float control system 29 comprises an irrigation float switch 31 and a town water control float switch 32. The float control system 29 as shown Figure 2 may also comprise a pump float switch 33. The irrigation float switch 31 is located 35 towards the top of the effluent storage tank 12 and provides a high water control for the effluent storage tank 12. The irrigation float switch 31 operates to H:\SherylM\Keep\Spcci\P62069.doc 7/09/06 - 6 control the level of treated effluent in the effluent storage tank 12 such that when it becomes too high (ie. when the float switch 31 rises to a specified level in the effluent storage tank 12) it signals the control box 30 to 5 discharge treated effluent from the tank 12. The control box 30 does this by opening a solenoid valve 34 on an irrigation line 35 to discharge treated effluent to a sprinkler system. The town water float switch 32 is located towards 10 the bottom of the effluent storage tank 12 and provides a low water control for the effluent storage tank 12. The town water float switch 32 operates to control the level of treated effluent in the effluent storage tank 12 such that when it becomes too low (ie. when the float switch 32 15 falls to a specified level in the effluent storage tank 12) it signals the control box 30 to flow town water into the effluent storage tank 12 via a town water inlet 36 to the tank 12. Thus, when the demand for treated effluent from the waste water treatment plant 10 exceeds the amount 20 of effluent produced to the extent that the effluent storage tank 12 is going to empty of water, the operation of the town water float switch 32 ensures that town water provides a back up source of water to ensure that there is always a flow of water to meet demand. 25 The pump float switch 33 is located towards the bottom of the effluent storage tank 12 and operates to control the effluent pump 26 such that when the level of water in the effluent storage tank 12 becomes too low the pump float switch 33 signals the control box to switch off 30 the effluent pump 26. The process of treating the waste water in the waste water treatment plant 10 generally begins by delivering waste water to the aerobic treatment chamber 11 through the inlet 20 and via the stilling well 21. 35 Although it is noted that a pre-treatment step may occur if the town water float switch 32 calls for town water to be delivered to the effluent storage tank 12 for use in H:\SherylM\Keep\Speci\P62069.doc 7/09/06 -7 the fixtures from which the waste water flows to the inlet 20. Once the aerobic treatment chamber 11 has sufficiently filled with waste water, the process of s aerobic digestion is "kick-started" by adding a nutrient dose to the waste water. If treating solely grey waste water, it has been conventionally thought that it is not possible to treat grey water aerobically. However, by providing this nutrient dose, aerobic digestion is 10 possible because the nutrient dose provides enough material off which the bacteria required for aerobic digestion can feed. The nutrient dose comprises at least a source of food for bacteria. The source of food comprises a source of is carbon and/or a source of nitrogen, which in a preferred form of the invention are a sugar (glucose) and a nitrate (or urea), although any other suitable source of carbon and/or nitrogen may be used. The source of nitrogen is typically required because grey water generally has a 20 large imbalance of phosphates compared to nitrates. Typically grey water has high levels of phosphates due to detergents, washing powders and other cleaning agents being present in the water. The carbon provides a building block for the bacteria population to grow as there is 25 typically very little BOD in grey water. The nutrient dose may also comprise a flocculant, which in a preferred form of the invention is aluminium sulfate, although any other suitable flocculant may be employed. The flocculant bonds together the nutrient dose when it is added to the grey 30 water, ie. prevents it from dispersing. This is so that a significant biomass can build up to enable the aerobic treatment of the waste water. In a preferred form of the invention the nutrient dose added to the waste water -7A comprises each of a source of carbon (preferably glucose), a source of nitrogen (preferably urea) and a flocculant (preferably aluminium sulfate) at 0.1-1.0 grams per litre of waste water (preferably 0.3-0.7 3330518_1 (GHMatters) P57936.AU. 1 2/05/12 - 8 grams per litre, more preferably approximately 0.5 grams per litre). Once the nutrient dose has been added to the waste water, air is delivered periodically to the aerobic 5 treatment chamber 11 whereafter the waste in the treatment chamber 11 is allowed to settle and then the upper layer of relatively clear effluent is discharged via the decanter 13 into the effluent storage tank 12. As described above, the treated effluent in the effluent 10 storage tank is subsequently recycled for use in at least some of the fixtures from which the waste water treatment plant 10 receives waste water. Once the process has started and the waste water has had the nutrient dose added, regular nutrient dosing 15 is not required as the process is generally self perpetuating. However, occasional dosing may be required if the aerobic digestion rate decreases sufficiently. Furthermore, if the process is ever stopped or shut-down, then a nutrient does will be required to be added to the 20 waste water to start the process up again. In the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in 25 an inclusive sense, ie. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. It is to be clearly understood that although 30 prior art publication(s) are referred to herein, this reference does not constitute an admission that any of these documents forms part of the common general knowledge in the art in Australia or in any other country. H:\SherylM\Keep\Speci\P62069.doc 7/09/06

Claims

1. A process for solely treating grey waste water, the process comprising the steps of: 5 (a) collecting the grey waste water and not any raw sewage; (b) adding a nutrient dose to the collected waste water which is not raw sewage; and (c) subjecting the dosed waste water to aerobic 10 digestion.

2. A process as claimed in claim 1, wherein the grey waste water is unresponsive to step (c) without first performing step (b). 15

3. A process as claimed in either claim 1 or claim 2, wherein the step of aerobic digestion occurs in an activated sludge tank. 20

4. A process as claimed in any one of the preceding claims, wherein the nutrient dose comprises a flocculant and at least one of a source of carbon and a source of nitrogen. 25

5. A process as claimed in claim 5 wherein the source of carbon is added to the waste water at 0.1-1.0 grams per litre of waste water.

6. A process as claimed in either claim 4 or 5, wherein 30 the source of carbon is a sugar.

7. A process as claimed in claim 6, wherein the sugar is glucose. -10

8. A process as claimed in any of claims 4 to 7, wherein the source of nitrogen is added to the waste water at 0.1-1.0 grams per litre of waste water. 5

9. A process as claimed in any one of claims 4 to 8 wherein the source of nitrogen is a nitrate.

10. A process as claimed in any one of claims 4 to 8, 10 wherein the source of nitrogen is urea.

11. A process as claimed in any of claims 4 to 10, wherein the flocculant is added to the waste water at 0.1 1.0 grams per litre of waste water. 15

12. A process as claimed in any one of claims 4 to 11 wherein the flocculant is aluminium sulfate. 12. A nutrient dose for use in a process for treating 20 grey waste water according to any one of the preceding claims, the nutrient dose comprising at least one of a source of carbon and a source of nitrogen and a flocculant. 25

13. A nutrient dose as claimed in claim 12 comprising a mixture of glucose, urea and aluminium sulphate.

14. A process for treating waste water as substantially described herein, with reference to the accompanying 30 drawings 3330518_1 (GHMatters) P57936.AU.I 2/05112