Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2001-07-02
2004-08-10
Prince, Fred (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S615000, C210S630000, C210S920000, C435S174000
Reexamination Certificate
active
06773592
ABSTRACT:
FIELD OF INVENTION
This invention relates to a method of treating waste water. The invention has particular application to the treatment of waste water where there is a relatively long period before the waste water is discharged. This invention has particular but not exclusive application to the treatment of sewerage effluent and for illustrative purposes only reference will be made to this application.
PRIOR ART
The conventional method of treating sewerage involves firstly collecting sewerage effluent through a conduit system of sewerage conduits and delivering it to a sewerage treatment plant at or close to the site where the treated effluent will be released. At the conventional sewerage treatment plants, the sewerage effluent undergoes a series of anaerobic and aerobic incubations to remove waste including organic matter, other solids, nitrogen and phosphate and disinfection to reduce the number of pathogenic organisms in the sewerage effluent prior to its release.
As the sewerage effluent passes through the sewerage mains and pumping stations, the sewerage effluent becomes an incubating culture. The composition of the sewerage effluent is continuously changing during its passage. Many of the reactions promoted by the naturally occurring micro-organism populations are undesirable. And produce reaction products such as hydrogen sulphide and ammonia and possibly also other nitrogenous containing compounds such as mercaptans. For example they cause major odour problems in the areas near pumping wells and also produce nasty gaseous chemicals that tend to corrode the conduits and other surfaces in the conduit system.
Further when the sewerage reaches the sewerage plant it has deteriorated in the sense that it contains more complex chemicals and is more difficult to treat than when it entered the system. These chemicals have been generated by the reactions propagated by the naturally occurring micro-organism populations in the conduit system. As a consequence the treatment of the sewerage at the treatment plant involves more unit operations and is more technically difficult than would otherwise be the case.
For example a common problem is the proliferation of filamentous bacteria incubating in a nutrient rich environment. The foaming problem in aerobic tanks results in the need for additional treatment and extends the time for treatment before the treated sewerage effluent can be released. These problems cause the cost of treatment to rise.
In the specification the term “comprising” shall be understood to have a broad meaning similar to the term “including” and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step of group of integers or steps. This definition also applies to variations on the term “comprising” such as “comprise” and “comprises”.
SUMMARY OF THE INVENTION
According to one aspect of this invention there is provided a method of treating waste water passed through a conduit system comprising at least one conduit extending from at least one entry point to a discharge point and including at least one quiescent zone where water is at least temporarily slowed in its displacement towards the discharge point, the method including introducing an inoculum into the system at at least one primary inoculation site for facilitating its entry into the quiescent zone where it incubates and forms an inoculum culture that influences the type and quantity of certain micro-organism populations in the system both within the quiescent zone and downstream thereof, the inoculum culture encouraging micro-organisms that assist with the break down or degradation of organic compounds within the waste water and retarding micro-organisms that tend to form undesirable compounds from the organic compounds in the waste water
Applicant has noted that sustained high velocity water flow significantly retards production of negative effects in waste water streams. Conversely, applicant has noted that unfavourable organisms tend to flourish in these quiescent zones where they attach to the surfaces of the conduit and the like. The organisms attach to both submerged surfaces in contact with the water and exposed surfaces in contact with the gas or air space above the surface of the water. This incubation of cultures of the harmful micro-organisms in the quiescent zones occurs because of the fact that the water does not have a significant path length or longitudinal velocity in these zones. The cultures produce chemical compounds that release toxic gases, eg hydrogen sulphide, and compounds that attack the materials of the conduit, eg concrete.
Applicant has discovered that these same quiescent zones can be used to produce positive reactions in the waste water (i.e. partial break-down) by a careful process of introduction of beneficial organisms (i.e. those which work to effect break-down of organic matter in the waste stream without large scale production of negative substances or effects) to the system by incubating an inoculum. This allows organisms which would not otherwise flourish (or would otherwise be out-competed) to maintain viable populations. Put another way the micro-organism population can be altered to produce catabolic-type reaction products rather than more complex anabolic reaction products.
Thus an inoculum is introduced to a quiescent zone where it encourages the propagation of beneficial organisms and suppresses the growth of harmful organisms, ie that react with the waste compounds to produce undesirable compounds such as ammonia and hydrogen sulphide.
In this specification the term quiescent zone means a zone somewhere along the length of the pipe where the water flow is interrupted or at least significantly reduced. The typical flow through the conduit resembles plug flow where all water is travelling at the same speed through the conduit towards the discharge point. However in the quiescent zone the water does not significantly advance towards the discharge point although there may be internal mixing in the zone. A quiescent zone may for example be formed by a pumping well, a low point at the interconnection of two conduit sections or any other zone where part of the pipe is exposed and water vapour collects. A quiescent zone may also occur intermittently in a given conduit in relation to intermittent cycles of a pump or variations in volumes of flow through the conduit.
The culture incubated by the inoculum typically comprises both aerobic and anaerobic micro-organisms and the micro-organisms in the inoculum culture typically exist in a symbiotic relationship with each other. Thus when the micro-organisms in the inoculum culture are carried by the water into an anaerobic environment a viable population of aerobic organisms will remain and when the micro-organisms incubated by the inoculum culture are carried in the water into an aerobic environment a viable population of anaerobic micro-organisms will remain.
Applicant has noted that the cultures of undesirable micro-organisms which produce negative effects in waste water systems (e.g. odour, aggressive atmospheres) are largely located on the surfaces of the conduits in the quiescent zones as distinct from in the waste water itself. Accordingly it is the cultures on the surfaces of the quiescent zones which have to be addressed. Prior methods have assumed that cultures causing negative effects are resident primarily in the water as distinct from on the surfaces which is incorrect.
Typically the system includes at least one surface, typically a plurality of surfaces, in the quiescent zone and the miro-organisms formed by the inoculum adhere tenaciously to the surface/s of the system.
The surfaces may be formed by the conduits and the micro-organisms formed by the inoculum preferably have the ability to adhere at least as tenaciously to the surface/s as the harmful microorganisms in the system.
The introduction and nurturing of these beneficial organisms at specific sites and the resultant positive effects (and suppression of negative
Bellamy Kenneth Michael
Newton Robert Kingsley
LandOfFree
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