AU6033890A

AU6033890A - Wastewater treatment

Info

Publication number: AU6033890A
Application number: AU60338/90A
Authority: AU
Inventors: Frank L. Horsfall III
Original assignee: APPLIED BIOTECHNOLOGIES
Current assignee: BIOSPHERE Corp SA
Priority date: 1989-07-14
Filing date: 1990-07-16
Publication date: 1991-02-22
Also published as: AU4908093A; CA2036392A1; EP0434810A1; GB8916153D0; WO1991001278A1; JPH04505279A

Description

-i-

WASTE ATER TREATMENT

Wastewater treatment plants have been built all over the world for the purpose of removing organic, nitrogen and phosphorus containing wastes present in municipal wastewater as well as those -⁾ produced by industrial operations or a combination of both. These treatment plants rely primarily upon biological activity for the removal and stabilisation of these wastes. Collection of the products of the biological activity in the treatment plants is accomplished through physical techniques like sedimentation or air flotation.

It has been assumed for years that the appropriate varieties and numbers of the microorganisms needed for the processing of the wastewater by these treatment plants have been provided by those microorganisms present in the wastewater entering the plants . Information to the contrary has been reported in several publications and at international meetings during the last few years. In fact, reports of bacterial seeding of the treatment plants have lead to conclusions of improved removal efficiencies for organic and nitrogenous waste, increased hydraulic and organic loading capabilities and decreased costs of operation with respect to the aeration required or the biological solids produced within the wastewater treatment plants . Not only has there been a direct correlation between the seeding of the treatment plants with various bacteria and changes in the function of the plants, e.g. improved removal efficiency, decreased energy need and/or decreased biological solids (sludge) production, but the need for continuous seeding has been demonstrated through the termination of seeding with bacteria and the observation that the changes in function noted during seeding regress to levels prior to seeding. Observations like these lead to a kinetic model in which there is a dynamic relationship between the microorganisms entering the plant, those growing and dying within the plant, and those leaving the plant. Apparently the fate of various bacterial forms is that unless replenished on a continuous basis, they are lost in sufficient numbers to affect the performance of the plant. There are only several possible ways that bacteria may be lost from a wastewater treatment plant once they have entered its processes and begun growing. They may be starved by competition with other bacteria, eaten by the myriad of animal forms present in the biomass (a group of microorganisms functioning together) of the process, or be washed out with the effluent water after the treatment systems are completed. Obviously, some or all of these loss mechanisms may be operating at the same time.

These considerations build a picture of the function of wastewater treatment facilities as a dynamic system in which it is rare for steady state conditions to exist or persist. Instead, there is a constantly changing biomass population regulated by the varieties of food and microorganisms present in the influent to the plant and the growth and retention capabilities of the plant itself with respect to those microorganisms that are present in this biomass.

The present invention provides a method for insuring that the biomass within the treatment processes is optimised by the production and continuous feed of effective microorganisms, especially bacteria, that are capable of proliferating within the processes of wastewater treatment facilities for the purpose of improved biological performance and/or reduction of the cost of their operation. According to the invention there is provided a method of treating wastewater in a treatment plant which consists of taking a quantity of the effluent water from the plant before disinfection, using the microbiological or bacterial organisms in that quantity of effluent to seed growth of organisms in a growth tank and supplying organisms for wastewater treatment from the growth tank to the plant. The organisms from the growth tank are supplied to the influent of the plant.

A process of substrate induced recognition may be used to enhance and program the effect of the organisms, the growth tank being fed with predetermined particular organic materials and/or industrial products as the organisms grow. The organic materials and/or industrial products may be particulate.

Preferably the volume of organism containing water fed back from the growth tank each day to the plant is between 1 and 20 parts per million of the daily flow of the plant. Typically, the proportion may be between 5 and 10 parts per million per day.

It is preferred that the growth tan is provided with suitably formulated food for the organisms and is aerated. The growth tank may be provided with supplementary micro-organisms.

It is possible in accordance with a feature of the invention to provide that organisms derived from the plant are grown in a plurality of growth tanks under the same or differing conditions of ambience and/or food and/or preconditioning, and the products of the growth tanks are used individually or in predetermined combinations to provide specific system improvements or amelioration of conditions in the wastewater treatment plant. Reference will hereinafter by made to the accompanying drawing, of which the sole figure is a schematic block diagram of a wastewater treatment plan .

In the drawing, the following legends apply:

A - Primary Sedimentation Tank

B - Aeration Tank or Rotating Biological Contactor or Trickling Filter

C - Secondary Sedimentation Tank

D - Anaerobic Digester

E - Chlorine Contact Tank

F - Return Activated Sludge

G - Waste Activated Sludge

H - Primary Sludge

I - Digested Sludge

J - Influent Wastewater

K - Effluent Wastewater

LI - First Growth Tank

L2 - Second Growth Tank

L3 - Third Growth Tank

Because of the design of wastewater treatment plants, maintenance of the biological forms growing within its processes are provided through recycle systems like returning the concentrated sedimented solids, commonly referred to as "Return Activated Sludge (RAS)". Such systems rely on the idea that all the biological forms, including bacteria, will be concentrated during sedimentation. Biological forms that are not concentrated are lost with the effluent or discharge wastewater. Even in the cases of fixed film type wastewater treatment plants (e.g. trickling filters and rotating biological contactors), those microorganisms that do not adhere or are not trapped within the biological film performing the treatment are lost from the plant with its discharge wastewater. Using the discharge wastewater itself as a method of reseeding is not feasible because of the constraint of hydraulics and the need for reasonable contact times for the microorganisms to perform the cleaning function on the influent wastewater for which the plant is intended.

If, however, the discharge or effluent wastewater is used to provide this microbiological or bacterial seed, a suitably-sized growth tank can then be used to produce the microorganisms which are then fed back to the point at which the influent enters the treatment plant (figure 1 point J), the problem of loss of groups or species of microorganisms and bacteria can be eliminated without introducing large volumes of wastewater back into the wastewater treatment plant itself. This system is effective in preventing the loss of those microorganisms not amenable to sedimentation concentration and return through the conventional methods in practice now throughout the wastewater industry.

The system just discussed provides a means for preventing the loss of microbiological and bacterial forms already growing and proliferating within the treatment plant. It does not, however, provide for the introduction of microbiological or bacterial forms that may not be present either in the processes of the treatment plant or in the influent feeding the treatment plant. By seeding a growth tank LI used to grow those microorganisms and bacteria found in the discharge wastewater with soil microorganisms, bacteria found in natural sources (e.g. rich humus and topsoil) , as well as, commercially available preparations, a great variety of microorganisms and a potential seed culture can be developed. This will provide the broadest range of biological activity specific to the needs and acclimated for the efficient effective and cost saving management of the wastewater treatment plant regardless of its location, function, or source of influent wastewater. This system will be least susceptible to modulation and perturbation provided by large incursions of organic and hydraulic loading. It will also be insensitive to changes resulting from selective pressures from other types of microorganisms and losses of microorganisms due to conditions within the wastewater treatment plant and the natural fate of the bacteria not concentrated by the standard physical and biological processes within the operation of the treatment plant itself.

Recognising that many treatment plants have influents that contain higher than normal levels of particular (perhaps particulate) organic material like grease, for example, and/or a product contained in an industrial discharge that may enter the plant intermittently and/or at a relatively high concentration, it would be a significant advantage to pre-condition the microorganisms and bacteria which are fed to the functional processes of the wastewater treatment plant to be able better to grow on and metabolise these materials present in the influent to the plant at the greatest rate possible both upon the initial addition of the microorganisms and bacteria and during their function in the operating processes of the plant like the aeration tank. A process that could be incorporated into the growth system described below which would provide initial recognition to the bacteria of the particular organic material and/or the industrial product before they enter the treatment plant is called "Substrate Induced Recognition" (SIR) and involves a method of adding a particular organic material and/or the industrial product found in the influent or a similar compound to the growth media for the microorganisms and bacteria themselves, described below, at an appropriate level or concentration sufficient to allow for growth of the microorganisms and bacteria on the compound or substrate. For example in the case of grease, using a liquid edible oil, like olive oil, or in the case of the presence of hydrocarbons using 2 fuel oil, for example, to induce growth of microorganisms and bacteria on these substrates or food would provide the functional parts of the treatment plant with microorganisms and bacteria that are already actively growing on materials similar or identical to the compounds in the influent to the plant. An example of the method for the addition of such a compound which will provide for Substrate Induced Recognition (SIR) is 0.05% (0.5 grams per liter) olive oil added to the growth and conditioning media specified below. "Substrate Induced Recognition" (SIR) provides for significant enhancement and/or increase in the capability of the microorganisms and bacteria to recognise and accelerate the rate of utilisation (metabolism) of the specific waste materials related to the substrate present in the influent.

Induction is the process by which a compound initiates the synthesis of enzymes within the microorganism which provides the cell with the capability to identify and metabolise more quickly the compound which caused the induction to occur, as well as, chemically similar materials. This causes an increase in the efficiency and the rate of removal of the material in question by the most rapid utilisation of oxygen or the oxidation of the compounds in question in the aeration tank. An example of the actual technique f or the introduction of the microorganisms and bacteria grown i n t h e s y s t em de s cr i b ed i n t he i nve nt i on i s a s follows : METHOD

For example :

An amount of five (5) to ten (10) volumes, for example, of microorganisms and bacteria for each one million (10**) volumes of incoming wastewater per day should be introduced by feeding once or perhaps twice per day depending upon the duration of the treatment system provided by the wastewater treatment plant. For example, a growth and feeding system of one hundred (100) to two hundred (200) liters in volume would be sufficient to provide the microbiological and bacterial seed for a treatment plant having an average hydraulic flow of twenty million (20 x 10^) liters of influent per day.

The actual sequence of preparation, growth and addition of the resulting seed culture for the type system discussed above is as follows:

1) To two hundred (200) liters of treatment plant effluent (prior to any disinfection) and: a) inorganic media composed of salts, for example:

-0.1% Ammonium chloride or sulfate -0.1% Disodium or dipotassium phosphate -0.05% Epsom salts (magnesium sulfate) b) organic media composed of nutrients, for example:

-0.1% sodium or potassium salt of a short chain fatty acid like acetate, propionate, lactate or butyrate. -0.1% peptone, tryptone or yeast extract. c) Soil inoculum or other soil bacterial source including commercial preparations, 30 grammes to 1/2 kilogram in quantity. 2) Upon addition of the above ingredients, begin aeration of the growth tank LI containing the entire contents of the system. Aeration can be provided by a diffused air system employing 0.006 to 0.015 cubic meters per minute which is ample for the two hundred (200) liter tank. 3) Aeration should be continued for an appropriate period of time. The contents of the tank should then be added to the appropriate section of the wastewater treatment facility. This addition may be made so one half the volume of the tank is added to the appropriate section of the treatment plant at predetermined intervals (e.g. twelve hours). APPLICATIONS

There are several possible applications for which the microbiological and bacterial seed culture developed during the growth phase discussed above may be used. Each of these applications will require a separate set of conditions, application points and evaluations to be performed. Possible applications include: A) Enhanced Treatment (e.g. improved removal efficiency of biochemical oxygen demand [BOD] and suspended solids [SS]: The seed culture should be added to the point at which the influent enters the plant (figure 1 point J) or to the secondary process (e.g. the aeration tank [figure 1 point B].

B) Increased Hydraulic or Organic Loading

Capability: The seed culture should be added to the point at which the influent enters the plant (figure 1 point J) . C) Decreased Production or Generation of Biological Solids (Sludge) : The seed culture should be added to the point in the plant at which the solids are at their highest concentration (e.g. the return sludge line [figure 1 point F], It can also be added to the primary clarifier or the point at which the influent enters the plant (figure 1 point J) if processing of the primary solids is a concern and solids from the primary clarifier and the secondary system do not mix or come into contact within a flow- through section of the plant.

D) Grease and Scum Control: The seed culture should be added to the point at which the influent enters the plant (figure 1 point J) or upline in the sewer system as far as practical. In some cases it may be appropriate to grow the seed culture at a location other than the plant and inject it directly into the sewer.

E) Nitrification, Denitrification and Nutrient Removal: Seed cultures for each of these processes may e developed using the same physical equipment as previously indicated, but using different growth tanks Ll, L2 , L3 etc. The nutrient mixture for these seed cultures is different and must be used in conjunction with the process described in A) above - "Enhanced Treatment". Thus a mixture of the bacterial seed prepared for "Enhanced Treatment" and a mixture of the bacterial seed prepared for "Nitrification" must be added to the point at which the influent enters the plant (figure 1 point J) to provide for significant ammonia removal within the wastewater treatment plant, i.e. nitrification.

The growth media for the seed culture used for providing or enhancing nitrification must not contain organic material. An example of such a growth solution is as follows: inorganic media composed of salts, for example:

0.05% ammonium chloride or sulfate 0.05% disodium or dipotassium phosphate 0.01% Epsom salts (magnesium sulfate)

0.1% limestone or chalk particles nutrient mixture composed of, for example : 0.1% soda ash or bicarbonate of soda. During growth, the solution in which the seed culture is growing will become acidified, that is, will drop in pH. This is corrected by the addition of measured quantities of any basic inorganic solution (e.g. ammonium hydroxide, which is preferred) to maintain the pH of the growing seed culture between pH 7 and 8 and provide additional growth nutrients. Addition of this culture may be made in conjunction with the seed culture for "Enhanced Treatment".

F) Plant Stability or Recovery from a Hydraulic Shock or Organic Shock Load: This condition may also be produced from large fluctuations in pH, temperature, or inorganic solute concentration. The seed culture should be added to the point at which the influent enters the plant (figure 1 point J). The addition of the seed culture should be maintained through suspected loading problems since the seed culture will not have experienced contact with the shock load. Because the existing biomass ceases to grow and metabolise for a period of time when it experiences conditional shock, having microorganisms available to grow and reproduce immediately upon entry into the plant is the key to recovery from a shock.

G) Competition with Noisome Organisms (e.g. Filamentous Bacteria) : A group or type of microorganisms will predominate in a system because they find a favourable environment and possess the capacity to outgrow other existing biological forms. By imposing a continuous seed of rapidly growing and biochemically diverse microorganisms on the processes of the wastewater treatment plant, the opportunity for a single type of bacteria or microorganism to predominate or proliferate is minimised. The addition of the seed culture to the point at which the influent enters the plant (figure 1 point J) will control, as much as is biologically possible, the predominance of noisome organisms (e.g. filamentous bacteria).

Each of the applications of the seed culture described in A-G above will provide microorganisms which can proliferate in the various functional parts of the wastewater treatment plant . Direct determinations of the bacterial numbers in the treatment plant are possible using simple microbiological techniques like dilution plating using agar media to enumerate the bacteria present. It is a useful endeavour to perform these types of analyses in order to be convinced of the effect of introducing microbiological seed cultures into the wastewater treatment plant and to correlate the result produced on the treatment plant with a change in the number and diversity of the microbiological and bacterial flora within the treatment system under evaluation. In this way the quantity and diversity of the microorganisms within the treatment plant processes may be observed directly. The actual determinations of the bacterial numbers and techniques for preparation of the analytical systems, like the use of petri dishes, for those determinations discussed within the text go beyond the scope of this invention.

Claims

1. A method of treating wastewater in a treatment plant which consists of taking a quantity of the effluent water from the plant before disinfection, using the microbiological or bacterial organisms in the that quantity of effluent to seed growth of organisms in a growth tank and supplying organisms for wastewater treatment from the growth tank to the influent of the plant.

2. The method as claimed in claim 1 wherein the organisms from the growth tank are supplied to the influent of the plant.

3. The method as claimed in claim 2 wherein substrate induced recognition is used to enhance and program the effect of the organisms, the growth tank being fed with predetermined particular organic materials and/or industrial products as the organisms grow.

4. The method as claimed in claim 3 wherein the particular organic and/or industrial products are particulate .

5. The method as claimed in any of the preceding claims wherein the volume of organism containing water fed back from the growth tank each day to the plant is between 1 and 20 parts per million of the daily flow of the plant.

6. The method as claimed in claim 5 wherein the volume of organism containing water fed back from the growth tank each day to the plant is between 5 and 10 parts per million of the daily flow of the plant.

7. The method as claimed in any of the preceding claims wherein the growth tank is provided with suitably formulated food for the organisms and is aerated.

8. The method as claimed in any of the preceding claims wherein the growth tank is provided with supplementary microorganisms.

9. The method as claimed in any of the preceding claims in which organisms derived from the plant are grown in a plurality of growth tanks under the same or differing conditions of ambience and/or food and/or preconditioning, and the products of the growth tanks are used individually or in predetermined combinations to provide specific system improvements or amelioration of conditions in the wastewater treatment plant.