GB2285439A

GB2285439A - Providing microorganisms for use in waste treatment

Info

Publication number: GB2285439A
Application number: GB9324977A
Authority: GB
Inventors: Jonathan Desmond Harper
Original assignee: Mass Transfer Ltd
Current assignee: Mass Transfer Ltd
Priority date: 1993-12-06
Filing date: 1993-12-06
Publication date: 1995-07-12
Also published as: GB9324977D0

Abstract

In order to provide a controlled population of active microorganisms to a biological waste treatment reactor, a vessel is provided for cultivating the microorganisms, which are fed directly into the reactor.

Description

PROVIDING MICROORGANISMS FOR USE IN WASTE TREATMENT The present application relates to an apparatus for providing microorganisms for use in a biological waste treatment process and a biological waste treatment plant comprising such apparatus.

Microorganisms, typically bacteria, are widely used to treat waste, particularly waste water such as sewage, by digestion or degradation of solids or pollutants in the waste. Commonly, the microorganisms used are cultivated specially and stored, for example in freeze dried, air dried or liquid form. When required, the microorganisms are fed into a biological waste treatment reactor with the waste to be treated, where they multiply and act on the waste.

The microorganisms are stored in a form in which their activity is very low, so that they can be stored for long periods of time. When the microorganisms are fed into the reactor, there is a delay before the activity and population of the microorganisms reaches the level required to degrade or digest solids or pollutants in the waste.

There is a danger that chemicals at toxic concentrations may be included in the waste fed into the reactor, which will impair the microorganisms or even kill them. Once toxic material has entered a reactor, the microorganism population of the reactor has to re-established from stored microorganisms before the reactor can resume normal activity.

The present invention provides an apparatus for providing microorganisms for use in a biological waste treatment process, comprising a vessel for cultivating the microorganisms and means for feeding the microorganisms from the vessel into a biological waste treatment reactor.

The present invention further provides a biological waste treatment plant, comprising, in combination, an apparatus for providing microorganisms as defined above and a biological waste treatment reactor.

In the apparatus of the invention, microorganisms can be cultivated in the vessel, so that a supply of microorganisms is available when the conditions in the reactor are not optimum for cultivating microorganisms, or when the reactor is not in use, or if material in toxic concentrations is released into the reactor.

The invention is suitable for use with any known waste treatment microorganisms, the type of microorganism used depending upon the waste treatment process used and the waste to be treated. The microorganisms may suitably be bacteria or mixed cultures of the type which reduce the biological or chemical oxygen demand of the waste by digestion or degradation of solids or pollutants in the waste. The invention may be used with known processes to treat industrial or domestic waste water such as sewage, or ground waters or leachates For example, the present invention may be used in aerobic biological waste water treatment processes such as suspended culture or activated sludge processes, trickling filter processes, submerged fixed growth or biologically aerated filter processes.

The invention may similarly be used in anaerobic biological waste water treatment processes such as the upflow sludge blanket process.

In use, the microorganisms may be supplied into the vessel in any known form, for example freeze dried, air dried (onto bran or any other suitable medium), in liquid suspensions, as recycled material from the biological waste treatment reactor or any other suitable form.

Conventional apparatus for feeding the microorganisms into the vessel may be provided. For example, where bran based microorganisms are used, they may be fed into the vessel via a hopper and weigh feeder system. The microorganisms may be fed into the vessel continuously or in batches.

When in use, the vessel will contain a liquid in which microorganisms are cultivated, for example water, sludge or slurry. Such media are relatively easy to transfer to the biological waste treatment reactor by a simple pump or gravity feed system.

Apparatus may be provided for adding substances to the vessel for controlling and/or assisting the cultivation of the microorganisms. For example, nutrient(s), including carbon sources, may be added. Acid or alkali of a suitable concentration may be added to maintain the pH in the vessel, the choice of acid or alkali depending upon the pH of the substances produced by the microorganisms, as will be apparent to the person skilled in the art.

According to a preferred embodiment, feed means are provided for feeding to the vessel a part of the waste to be treated in the reactor. In this way, a readily available source of nutrient, including material for the microorganisms to digest or degrade, can be provided for the microorganisms. Furthermore, the microorganisms can be acclimatised to the environment in the reactor before being fed into it. For example, about 1 to 10%, preferably 5% of the waste to be treated may be fed into the vessel.

It is preferred that the feed means comprises at least two tanks, there being means for feeding waste to the tanks in alternation and means for feeding waste to the vessel, the feed means being controllable so that waste is fed from whichever tank is not receiving waste. In this way, if chemicals in toxic concentrations enter the waste, at least one of the tanks will contain a supply of waste free from chemicals in toxic concentration, which can fed into the vessel while the toxic material is cleansed from the reactor.

Means for feeding nutrient to the vessel may be provided including means for feeding to the vessel a carbon source for the microorganisms. Such means may be provided as an alternative or backup to the means for feeding waste to the vessel.

Heating means may be provided in the vessel to control the temperature in the vessel.

It is preferred that means are provided for sensing and controlling the conditions in the vessel. For example, means may be provided for giving signals dependent upon the conditions in the vessel, for example the pH, nutrient concentration and temperature. The signals may be input to means for controlling the rate at which nutrient, acid/alkali or heat is fed to the vessel.

Where an aerobic system is used, means may be provided for blowing air through the vessel.

The apparatus of the invention can be used to establish a population of microorganisms in a waste treatment reactor when it is commissioned or recommissioned after cleaning. The apparatus may also be used to increase the microorganism population in the reactor if the source of waste to the waste treatment reactor has been low or if there is a sudden increase in the quantity of waste to be treated or if a chemical not normally present is introduced into the waste to be treated. The apparatus of the invention may be used to supply microorganisms substantially continuously to a waste treatment reactor in order to allow the population of microorganisms in the waste treatment reactor to be accurately controlled.

The present invention allows the time for the establishment of a sufficient active population of microorganisms in the waste treatment reactor to be greatly reduced, as a separate, optimally controlled vessel is provided for cultivating the microorganisms.

In a particularly preferred embodiment of the waste treatment plant of the invention, means are provided for giving signals representative of the conditions in the vessel and the waste treatment reactor to a central processor, the central processor providing signals for controlling conditions in the vessel and the rate of transfer of microorganisms from the vessel to the reactor in response to the signals from the sensors.

Means may be provided for controlling the rate of feed of microorganisms to the vessel and from the vessel to the waste treatment reactor so that the average residence time of microorganisms in the vessel is sufficient for the microorganisms to become acclimatised to the waste being treated and for the population of microorganisms to enter the exponential growth phase.

The concentration of microorganisms in the material fed to the reactor will depend upon the waste treatment process being used, and will be apparent to the person skilled in the art. However, the concentration is preferably in the range 500 to 3,000mg/l.

The volume of the vessel may be small compared to that of the waste treatment reactor. For example, the ratio of the volumes of the reactor and the vessel may be in the range of 3:1 to 10:1. The ideal conditions for cultivating the microorganisms may not be the same as the ideal conditions for maximising the rate of treatment of the waste. According to a preferred embodiment, conditions in the vessel are maintained so as to give the optimum rate of growth of microorganisms, microorganisms being continuously fed to the reactor to maintain the microorganism population at a level which would not otherwise be possible, given the conditions in the reactor. The size of the vessel compared to the reactor will depend upon the rate at which microorganisms need to be fed into the reactor.

The present invention will be further described by way of example only with reference to the accompanying drawing, which is a schematic illustration of a biological waste treatment plant according to the invention.

The apparatus 1 shown in the figure is illustrated using conventional symbols.

The apparatus 1 comprises a vessel 10 for cultivating microorganisms and a biological waste treatment reactor 20 for the bacterial treatment of waste water.

The bacteria to be used in reactor 20 are first fed into the cultivating vessel 10 by a hopper and weigh-feeder system 11. The bacteria 11 are supplied in freeze-dried or liquid form and are fed into the liquid 12 in the vessel 10. Conditions in the vessel 10 are maintained so that the freeze-dried bacteria or suspensions thereof in liquid become active and start to multiply.

The liquid 12 from the vessel 10 is fed by a gravity discharge line 13 to the reactor 20. In the reactor 20, the bacteria act on waste water which is fed into the reactor 20 by an input line 21. Treated waste water is discharged from the reactor 20 by a discharge line 22, for release into the environment or further treatment.

The liquid 12 in the vessel 10 is supplied either from the waste water input line 12 of the reactor 20 along a line 30, or by a back-up system 40 which may be used when the supply of waste water is cut off or low.

By feeding waste water into the vessel 10, the bacteria in the liquid 12 in the vessel 10 may become acclimatized to the waste water to be treated.

Waste water from line 30 may be fed either into a tank 31 or a tank 32. When the tank 31 is receiving waste water, the supply of waste water to tank 31 is shut off, and vice versa. Waste water is pumped from whichever of the tanks 31 and 32 is not receiving waste water along the respective supply line 33 or 34 to the vessel 10.

In this manner, if the liquid flowing along the waste water input line 21 contains chemicals in toxic concentrations, the toxic material will only be fed into whichever of the tanks 31 or 32 is currently receiving waste water. The other tank will remain free of material in toxic concentrations, and a supply to the vessel 10 of waste water free of material in toxic concentrations may be continued for some time.

The back-up system 40 is a system for supplying liquid 12 to the vessel 10 if the waste water supply 21 to the reactor or from the tank 31 or 32 is cut off. The back-up system 40 comprises a supply 41 of potable water, for example from the mains water supply, a tank 42 for holding nutrient for the bacteria in the vessel 10 and a tank 43 for holding a carbon source to be digested by the bacteria. When necessary, material is pumped from the tanks 42 and 43 to the vessel 10 along with water from line 41.

Drains 14, 23, 35 and 36 are provided for the vessel 10, reactor 20 and tanks 31 and 32 respectively, in order to allow these vessels to be drained for routine maintenance or for cleansing toxic material.

Conventional means are provided for controlling the conditions of pH, nutrient content and temperature in the reactor 20.

Sensor means 15 are provided for sensing the conditions of pH, temperature and nutrient concentration in the vessel 10. The sensor means 15 gives signals to a central processor representative of the above mentioned conditions. In response, the central processor gives signals to a system 16 to add acid and/or alkali to adjust the pH if necessary, or to tank 42 to feed nutrient to the vessel 10. Heating means 17 controlled by the central processor is provided for controlling the temperature of the liquid 12 inside the vessel 10.

Aeration means 18 may be provided, comprising a blower and perforated plenum, to ensure that conditions in the vessel 10 are aerobic, if required. An agitator 19 is provided to circulate the liquid 12 in the vessel 10.

The central processor (not illustrated) can control the conditions in the vessel 10 to optimize the rate of cultivation of bacteria. Accordingly, the bacteria from feeder 11 may be activated and cultivated at the optimum rate, independently of conditions in the reactor 20.

Similarly, conditions in the reactor 20 may be controlled to ensure optimum rate and quality of treatment of the waste water independently of conditions in the vessel 10. The central processor can give signals to a valve in the gravity feed line 13 to control the supply of bacteria from vessel 10 to reactor 20, to establish or maintain the optimum population of bacteria in the vessel 20.

The present invention has been described above purely by way of example, and modifications can be made within the spirit of the invention. The invention also consists in any individual features described or implicit herein or shown or implicit in the drawings or any combination of such features or any generalization of any such features or combination.

Claims

1. Apparatus for providing microorganisms for use in a biological waste treatment process, comprising a vessel for cultivating the microorganisms and means for feeding the microorganisms from the vessel into a biological waste treatment reactor.

2. Apparatus according to Claim 1, further comprising feed means for feeding to the vessel a part of the waste to be treated in the reactor.

3. Apparatus according to Claim 2, wherein the feed means comprises at least two tanks, there being means for feeding waste to the tanks in alternation and means for feeding waste from the tanks to the vessel, the feed means being controllable so that waste is fed from whichever of the tanks is not receiving waste.

4. Apparatus according to any of the preceding claims, further comprising means for feeding to the vessel a carbon source for the microorganisms.

5. Apparatus according to any of the preceding claims, further comprising means for controlling the conditions in the vessel.

6. Apparatus according to Claim 5, further comprising means for giving signals dependent upon the conditions in the vessel, and means controllable in response to said signals for feeding substances and/or heat to the vessel.

7. Apparatus according to any of the preceding claims, wherein the volume of the vessel is small compared to the volume of the waste treatment reactor.

8. A biological waste treatment plant, comprising, in combination, an apparatus for providing microorganisms as defined in any of Claims 1-7, and a biological waste treatment reactor.

9. Apparatus for providing microorganims for use in a biological waste treatment process, substantially as herein described with reference to the accompanying drawing.

10. A biological waste treatment plant, substantially as herein described with reference to the accompanying drawing.