AU630512B2

AU630512B2 - Anaerobic treatment of effluent

Info

Publication number: AU630512B2
Application number: AU63640/90A
Authority: AU
Inventors: Trevor Redvers Bridle; Christopher Kurt Hertle
Original assignee: CAMPBELL ENVIRONMENTAL Ltd
Current assignee: Tenix Alliance Pty Ltd
Priority date: 1989-10-06
Filing date: 1990-09-26
Publication date: 1992-10-29
Anticipated expiration: 2010-09-26
Also published as: AU6364090A

Description

rt 630 12 COMMONWEALTH OF AUSTRALIA Patents Act 1952 COMPLETE SPECIFICATION (Original) FOR OFFICE USE Application Number: PJ6753 Class Lodged: 6 October, 1989 Int. Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: 0 TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: CAMPBELL ENVIRONMENTAL LIMITED of Suite 93, Havelock Mall, City West, West Perth, in the State of Western Australia, Commonwealth of Australia.

Actual Inventors: TREVOR REDVERS BRIDLE and CHRISTOPHER KURT HERTLE Wray Associates Primary Industry House 239 Adelaide Terrace Address for Service:- Perth Western Australia 6000.

Complete Specification for the invention entitled: "Anaerobic Treatment of Wastewater" The following statement is a full description of this invention, including the best method of performing it known to me:- 1 2 The present invention relates to a process and apparatus for anaerobic treatment of organic wastewaters. More particularly, the invention relates to a process and apparatus for conversion of the biodegradable fraction of wastewaters under anaerobic conditions for the purpose of reducing the strength of the wastewaters to minimise sewer charges and/or reduce the effect of the wastewater on the environment and obtaining useful products, such as gaseous fuels, from the wastewaters.

Biological treatment (aerobic and anaerobic) has been utilised for the treatment of high strength industrial wastewaters for many years. It has previously been restricted by economics of the processes utilised due to excessive capital and operating costs and operational 15 problems. This has forced many industries to dispose of wastewaters directly to sewer or to inefficient and odorous lagoon systems. However the recent development of high-rate S. anaerobic treatment of industrial wastewaters has made biological operations an extremely cost-competitive option.

20 In anaerobic pre-treatment, the choice of system has ranged .from a variety of fixed film systems to different types of suspended bed technologies. Fixed films offer a stable bacterial environment but are not capable of removing the same quantity of suspended solids and oil and grease as suspended bed systems. Furthermore, certain types of fixed film systems are prone to clogging and require frequent, expensive maintenance. Suspended beds, on the other hand, are not resistant to sudden variations in feed characteristic shock loads of flow or strength) which can damage the system. They also require the formation of granular type sludge, or at worst as well flocculated sludge, to ensure solids carryover is not excessive.

3 The present invention seeks to address the aforementioned limitations of existing anaerobic treatment systems by providing a process and apparatus for anaerobic treatment of wastewaters which offer relatively high rates of pollutant removal and resistance to sudden variations in feed characteristics.

In one form the invention resides in apparatus for anaerobic treatment of wastewater comprising a reaction chamber defined by wall means having a lower portion generally o o 10 circular in horizontal cross-section, said reaction chamber o having upper and lower zones, said upper zone containing a means for supporting micro-organisms for anaerobic r, ireactions, inlet means for introducing wastewater into the lower zone and outlet means for removing a treated liquid component of the wastewater and biologically produced gas from the upper zone, wherein said inlet means cooperates with said lower portion of said wall means to generate a flow of wastewater in said lower zone which flow circulates about a substantially vertical axis and rises upwardly through said lower zone towards said upper zone.

a aWith this arrangement a primary anaerobic treatment is performed on the wastewater in the lower zone. Sludge in the lower zone also serves to treat the wastewater by trapping particulates and oil and greasy wastes. A secondary anaerobic treatment is performed in the upper zone. There is some overlap of the primary and secondary treatments in the two zones.

The circulating and upward flow of the wastewater in the lower zone establishes a suspended bed within the lower zone for maintaining flocculent or granular sludge derived from primary anaerobic treatment of the wastewater in the lower zone. In this way, wastewater substantially free of sludge moves upwardly through the upper zone for purification by *0 ~9 4 said secondary anaerobic treatment. The manner in which the wastewater is introduced into the reaction chamber allows for effective sludge formation and also ensures good contact between the wastewater and the sludge, and plug-flow through the reaction chamber.

Preferably, said lower portion comprises a bottom wall of the reaction chamber, said bottom wall being substantially hemispherical in one embodiment and substantially conical in another embodiment.

Preferably, said inlet means comprises at least one nozzle for injecting wastewater into said lower zone in a direction downwardly and sidewardly towards said bottom wall.

o. Preferably, said wall means includes a substantially cylindrical side wall above said lower portion. The side wall above side lower portion may however be of any other configuration such as rectangular.

Preferably, said means for supporting micro-organisms in the upper zone comprises a packing medium within the upper zone.

Conveniently, said packing medium is in the form of conventional "bio-rings".

Preferably said outlet means comprises a first outlet for removal of the treated liquid component of the wastewater and a second outlet for removal of the biologically produced gas.

In another form the invention resides in a method of anaerobic treatment of wastewater comprising the steps of: introducing wastewater into a reaction chamber to generate a flow which circulates about a substantially vertical axis and which moves upwardly in the chamber to create a suspended bed of flocculent sludge and/or granular o 5 sludge for a primary anaerobic reaction process; passing a liquid component of the wastewater through a secondary anaerobic reaction process; and removing treated wastewater and biologically produced gas from the reaction chamber.

Preferably, the wastewater is introduced into the reaction chamber Dy injection.

Preferably, said flow of the wastewater is plug-flow upon entering said anaerobic process.

Preferably portion of said wastewater is removed from the reaction chamber before undergoing said secondary anaerobic reaction process and returned to the chamber with untreated wastewater.

Preferably, said method is performed in apparatus as set forth hereinbefore.

The invention will be better understood by reference to the following description of one specific embodiment thereof as shown in the accompanying drawings in which:- Fig. 1 is a schematic view of an apparatus according to the embodiment; Fig. 2 is a cross-sectional view of the lower portion of the apparatus showing nozzles for introducing wastewater into the reaction chamber; Fig. 3 is a side elevational view of Fig. 2; and Fig. 4 is a plan view of an extraction manifold for extracting sludge from within the reaction chamber prior to secondary anaerobic treatment.

The embodiment shown in the drawings is directed to apparatus for anaerobic treatment of wastewater with a high fraction of oil and grease materials, such as effluent 6 derived from abattoirs, wool scouring operations and dairies.

The apparatus comprises a reaction chamber 11 defined by wall means 13 including a cylindrical side wall 15, a substantially hemispherical bottom wall 17 and a top wall 19. The bottom wall 17 may be of a configuration other than hemispherical, such as conical, the essential feature being that the inner surface thereof be generally circular in horizontal cross-section to allow a circulating flow to be established, as will be explained later. The chamber is formed in two sections 21 and 22 having mounting flanges or joints 23 and 24 respectively which are bolted, welded or otherwise secured together. The chamber may be supported above the ground on a frame structure The chamber is divided into upper and lower zones 27 and 29 respectively, the upper zone 27 being contained within section 21 and the lower zone 29 being contained within section 22. A primary anaerobic treatment process is performed predominantly in the lower zone and a secondary anaerobic treatment process is performed predominantly in the upper zone, although there is some overlap between the process in the two zones.

The upper zone 27 of the reaction chamber contains means for supporting micro-organisms for the secondary anaerobic reaction process. in this embodiment, such means comprise a packed bed of conventional "bio-rings".

An inlet 31 is provided for introducing wastewater into the lower zone 29 and a first outlet 33 is provided for removing treated liquid from the upper zone 27.

The inlet 31 comprises an inlet line 34 and a plurality of inlet nozzles 35 circumferentially spaced around the r- 7 hemispherical bottom wall section of the chamber. A feed pump 36 is provided in the inlet line 34. Each nozzle 35 is arranged to direct wastewater toward the bottom wall 17 of the reaction chamber in a direction which is both downwardly and sidewardly so as to generate a circulating flow within the lower portion of the reaction chamber, as shown in Fig.

2 of the drawings. The downward and sideward direction of the nozzles cooperates with the hemispherical shape of the bottom wall of the reaction chamber to generate a smooth rotating circulation pattern within the lower portion of the zone contained within the lower section 22. The incoming wastewater flows upwardly through the lower zone 29 and establishes a suspended bed for the primary anaerobic treatment which results in formation of a flocculent sludge with good settling properties. The sludge also treats the wastewater by physically trapping particulates and any oil and greasy wastes present in it. By the time the wastewater reaches the upper zune 27, plug-flow has been established and much of the solid matter initially in the wastewater has been removed. The wastewater flows upwardly through the anaerobic reaction bed in the upper zone 27 and undergoes purification by the secondary anaerobic reaction treatment performed by micro-organisms supported in the zone. The micro-organisms are supported on the "bio-rings" and are essentially immobilised and unable to leave the reaction chamber. This provides for excellent resistance to process upsets by carrying a large population of immobilised microorganisms, maintaining treatment performance under adverse conditions.

The treated wastewater leaves the reaction chamber by way of the first outlet 33. The first outlet means 33 includes a circular weir 37 over which the treated liquid flow into launder 39 from which the liquid is removed by way of an outlet line 41 for subsequent disposal. The outlet line 41 includes a gas valve 43 in the form of a syphon for 8preventing entry of air into the reaction chamber or allowing bio-gas to escape by way of the liquid outlet means. The outlet line incorporates a temperature senisor and a meter 47 for determining the pH level of the treated liquid.

An extraction means 49 provided for selectively extracting sludge from the reaction chamber at or near the top of the lower zone 29. The extraction means is in the form of a manifold having radial arms 51 each provided with a plurality of inlet openings 53. The extraction means 49 is connected to a return li.ne 55 by way of a control valve 57.

The return line 55 is connected to the inlet line 34 of the inlet means 31. A recycling pump 59 is incorporated in the return line 55. The construction of the manifold facilitates a generally uniform rate of extraction of wastewater across the reaction chamber with little disturbance to the uniform upward flow of the body of the wastewater.

By recycling sludge mixture removed by way of the extraction means 49, it is possible to regulate the upward velocity of wastewater in the lower zone and hence prevent movement of solids into the upper zone 27. A flow rate of less than metres per hour is desirable. Recycling allows for the system to operate satisfactorily with a dispersed sludge.

Provision is also made to selectively recycle treated liquid removed from the reaction chamber by way of the outlet means 33. In this connection, further return line 61 extends between outlet line 41 and return line 55. A control valve 63 is provided in return line 61.

9 The purpose of recirculating the treated liquid is to ensure that contents within the reaction chamber do not inhibit micro-organism activity.

An injection system 65 is provided for selectively injecting chemicals into the inlet line for the purpose of controlling the pH level of the wastewater entering the reaction chamber.

Means (not shown) are provided for regulating the temperature within the reaction chamber. For preference, the temperature is maintained at 36 3 C which is the optimal mesophylic anaerobic temperature.

A second outlet 67 which is in the form gas collection means provided at the top of the reaction chamber, is provided for removal of bio-gas generated during the anaerobic reaction process.

A gas conservation breather vent 68 is provided at the top of the reaction chamber for releasing gas during high pressure situations.

A drain valve is provided for selectively draining accumulated sludge from the reaction chamber.

Operation of the apparatus and the treatment process can be readily understood from the foregoing description.

By way of example, numerical data for the treatment of abattoir and septage wastewater in apparatus according to the invention are set out below.

L

I

10 Wastewater Spatial COD loading rate COD Feed COD Discharge Temperature in reactor pH in reactor

CH

4 content of the gas Oil and Grease removal Solids removal

BOD

5 removal kg/m3/d mg/L mg/L 3C vol Abattoir 8 1500 400 25-35 6.6-7.2 55-70 66 60 65 Septage 5-7 3000 900 30-35 6.5-7.4 70-80 70-90 It should be appreciated that the scope of the invention is not limited to the scope of the embodiment described.

N

Claims

6. A THE CLAIMS defining the invention are as follows:- plural reacti 1. Apparatus for anaerobic treatment of wastewater comprising a reaction chamber defined by wall means
7. A having a lower portion generally circular in horizontal nozzle cross-section, said reaction chamber having upper and reacti lower zones, said upper zone containing a means for supporting micro-organisms for anaerobic reactions, inlet means for introducing wastewater into the lower 8. Al zone and outlet means for removing a treated liquid organi component of the wastewater and biologically produced organi within gas from the upper zone, wherein said inlet means cooperates with said lower portion of said wall means
9. AI to generate a flow of wastewater in said lower zone claims which flow circulates about a substantially vertical outlet axis and rises upwardly through said lower zone towards the w said upper zone. biologj 2. Apparatus according to claim 1 wherein said lower A portion comprises a bottom wall of the reaction t. t :outlet chamber. componE an out 3. Apparatus according to claim 2 wherein said bottom wall is substantially hemispherical.
11. A 4. Apparatus according to claim 2 wherein said bottom wall is substantially conical. is pr from en Apparatus according to any one of the preceding and t liquid. claims wherein said inlet means comprises at least one nozzle for injecting wastewater into said lower zone in
12. Ap a direction downwardly and sidewardly towards said claims bottom wall. extract section z t~:~~nrr 12 6. Apparatus according to claim 5 wherein there are a plurality of said nozzles spaced uniformly within the reaction chamber cross-sectional area. 7. Apparatus according to claim 6 wherein said nozzles are circumferentially spaced around the reaction chamber. 8. Apparatus according to any one of the preceding claims wherein said means for supporting micro- organisms in the upper zone comprises a packing medium within the upper zone. 9. Apparatus according to any one of the preceding claims wherein said outlet means comprises a first outlet for removal of the treated liquid component of the wastewater and a second outlet for removal of the biologically produced gas. Apparatus according to claim 9 wherein said first outlet includes a weir over which the treated liquid component of the wastewater flows into a reservoir and an outlet flow line for conveying the treated liquid from the reservoir. 11. Apparatus according to claim 10 wherein a gas seal is provided in said outlet flow line to prevent air from entering the reaction chamber along said flow line and to allow disentrainment of gas from the outflowing liquid. 12. Apparatus according to any one of the preceding claims wherein extraction means are provided for extracting wastewater from the region at the upper section of the lower zone. 13
13. Apparatus according to claim 12 wherein recirculating means are provided for recirculating wastewater extracted by said extraction means and returning it to the inlet means.
14. Apparatus according to claim 13 wherein further recirculatory means are provided for returning portion of treated liquid removed by the outlet means to the inlet means. Apparatus according to any one of the preceding claims further comprising means for selectively draining the reaction chamber.
16. A method of anaerobic treatment of wastewater comprising the steps of: introducing wastewater into a reaction chamber to generate a flow which circulates about a substantially vertical axis and which moves upwardly in the chamber to create a suspended bed of flocculent sludge and/or granular sludge for a primary anaerobic reaction process; passing a liquid component of the wastewater through a secondary anaerobic reaction process; and removing treated wastewater and biologically produced gas from the reaction chamber.
17. A method according to claim 16 wherein the wastewater is introduced into the reaction chamber by injection.
18. A method according to claim 16 or 17 wherein said flow of the wastewater is plug-flow upon entering said anaerobic process. r 14
19. A method according to claim 16, 17 or 18 wherein portion of said wastewater is removed from the reaction chamber before undergoing said secondary anaerobic reaction process and returned to the chamber with untreated wastewater. Apparatus for anaerobic treatment of wastewater substantially as herein described with reference to the accompanying drawings.
21. A method of anaerobic treatment of wastewater substantially as herein described. DATED this eighth day of June, 1992 CAMPBELL ENVIRONMENTAL LIMITED Applicant WRAY ASSOCIATES Perth, Western Australia Patent Attorneys for Applicant a.