WO2014108864A1 - Biological wastewater treatment processes that enhances the capacity for polyhydroxyalkanoate accumulation in a mixed culture biomass - Google Patents
Biological wastewater treatment processes that enhances the capacity for polyhydroxyalkanoate accumulation in a mixed culture biomass Download PDFInfo
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- WO2014108864A1 WO2014108864A1 PCT/IB2014/058187 IB2014058187W WO2014108864A1 WO 2014108864 A1 WO2014108864 A1 WO 2014108864A1 IB 2014058187 W IB2014058187 W IB 2014058187W WO 2014108864 A1 WO2014108864 A1 WO 2014108864A1
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/02—Aerobic processes
- C02F3/12—Activated sludge processes
- C02F3/1236—Particular type of activated sludge installations
- C02F3/1263—Sequencing batch reactors [SBR]
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/30—Aerobic and anaerobic processes
- C02F3/302—Nitrification and denitrification treatment
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- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
- C12P7/00—Preparation of oxygen-containing organic compounds
- C12P7/62—Carboxylic acid esters
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- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
- C12P7/00—Preparation of oxygen-containing organic compounds
- C12P7/62—Carboxylic acid esters
- C12P7/625—Polyesters of hydroxy carboxylic acids
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2203/00—Apparatus and plants for the biological treatment of water, waste water or sewage
- C02F2203/004—Apparatus and plants for the biological treatment of water, waste water or sewage comprising a selector reactor for promoting floc-forming or other bacteria
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
Definitions
- BIOLOGICAL WASTEWATER TREATMENT PROCESSES THAT ENHANCES THE CAPACITY FOR POLYHYDROXYALKANOATE ACCUMULATION IN A MIXED CULTURE
- Biodegradable polymers by biomass, such as that in activated sludge treating wastewater.
- the harvested biomass can be made to accumulate significant levels of biopolymers and the now biopolymer-rich biomass is no longer a disposal problem but is, to the contrary, a raw material resource in the value chain towards bioplastics and/or fine chemicals. In this manner a sludge disposal problem may be turned into a renewable resource opportunity.
- PHAs polyhydroxyalkanoates
- Feast and famine means that the biological treatment is carried out such that the biomass is exposed to alternating environments of available and scarcely available substrate in the form of readily biodegradable COD (RBCOD).
- RBCOD may, for example, include volatile fatty acids such as acetic acid.
- acetic acid One gram mass of acetic acid is equivalent to 1 .067 grams of acetic acid as chemical oxygen demand or COD.
- a typical minimal background PAP for activated sludge is an ability to store PHA to a level less than about 20 % g-PHA/g-VSS.
- An enriched PAP may be considered to be an accumulation potential of about 30% or more, and preferably more than 50% g-PHA/g-VSS.
- a high PAP makes the accumulation process and subsequent recovery of PHA more efficient and thereby improves the overall process economy of producing PHA as a by-product of services in water quality management by biological treatment.
- Production of PHA from services of water quality management can be a part of an overall biorefinery concept involving biological treatment unit processes comprising but not limited to:
- Optional pretreatment such as acidogenic fermentation in order to convert organic matter into RBCOD fermentation products such as volatile fatty acids (VFAs).
- VFAs volatile fatty acids
- Typical feast and famine selection of PAP has focused on maintaining stable conditions in time of a cyclic regime of feast and famine. This is to say that the biomass is exposed to repeated cycles of feast and famine, where the total feast-famine cycle time is approximately constant, and where the famine portion is generally meant to be greater than 3 ⁇ 4 of this cycle time.
- feast and famine selection has been repeatedly shown to enrich the PAP of a biomass produced in open mixed-cultures, results also suggest that the microbial community that comprises the biomass may adapt itself to the regime of feast-famine. By adaptation the microbial community may be less likely to directly reach its full potential of PAP during a PHA accumulation process.
- the present invention relates to a method of biologically treating wastewater with biomass and, in the process of treating the wastewater, enhancing the PHA accumulation potential that is expressed by the biomass.
- the biomass may be employed to remove BOD, nitrogen, phosphorus, and a wide range of contaminants commonly found in municipal and other types of wastewater or process water streams.
- a primary feast- famine (selection) process is employed.
- the primary feast-famine process subjects the biomass to repeated cycles of feast and famine conditions. These conditions are referred to as primary feast conditions and primary famine conditions.
- the number of repeated cycles of feast and famine conditions can vary.
- the biomass is exposed to at least two repeating cycles of alternating feast and famine conditions.
- the processes described herein involve the introduction of a controlled deviation or deviations from the cyclic primary feast-famine regime.
- the deviation process is referred to as a secondary famine process or simply a secondary perturbation.
- the biomass or a portion thereof is subjected to famine conditions for a period of time substantially greater than the average primary famine period.
- the secondary famine period is greater than the average of the proceeding primary famine periods but less than the solids retention time of the biomass in the process.
- the secondary famine process may be initiated periodically.
- peripheral famine process means from time-to-time and after a plurality of primary feast-famine cycles. That is, the secondary famine process need not be initiated based on fixed time intervals. Instead, the time intervals between successive secondary famine processes can vary. In some embodiments, the secondary perturbation occurs at least once every four sludge retention times (SRTs).
- SRTs sludge retention times
- the present disclosure is further directed to a process or method for enhancing the PAP of a biomass over and above what may be expected from subjecting the biomass to a fixed cyclic regime of feast and famine conditions.
- PAP of a biomass may be influenced by two factors. A higher PAP is demonstrated by a biomass enriched with a higher fraction of populations of bacteria with a metabolic capability to convert RBCOD into intracellular stored PHA. A higher PAP may also be due to the physiological state of the biomass at the time of the accumulation process.
- the feast and famine regime selects for preferred survival of populations of PHA storing bacteria in the biomass.
- the specific conditions of feast and famine also conditions those PHA storing bacteria to be prepared to not store more PHA than they need to store during feast.
- the level of PHA that is stored is low compared to the ultimate levels desired for the PHA accumulation process.
- the methods of the present invention aim to combine conditions of PAP enrichment with conditions that tend to maintain the biomass with an improved physiological state for PHA accumulation. Notwithstanding this interpretation, and the potential for other such interpretations, the present methods provide for augmented process conditions over and above those of the basic feast-famine strategy such that an enhanced performance in PHA accumulation is accomplished.
- Figure 1 is a schematic illustration of one embodiment of a semi-continuous flow biological wastewater treatment process that enhances the PHA accumulation potential in biomass employed in the biological process.
- Figure 2 is a schematic illustration of one embodiment of a continuous flow biological wastewater treatment process that enhances the PHA accumulation potential in biomass employed in the biological process.
- Figure 3 is a schematic illustration of another embodiment of a continuous flow biological wastewater treatment process that enhances the PHA accumulation potential in biomass employed in the biological process.
- Figure 4 is a schematic illustration of another embodiment of a continuous flow biological wastewater treatment process that enhances the PHA accumulation potential in biomass employed in the biological process.
- Figure 5 is a schematic illustration of a biological wastewater treatment process designed to nitrify and denitrify wastewater and, at the same time, enhance the PHA accumulation potential in biomass employed in the process.
- Figure 6 is a graphical illustration of PHA accumulation potential for biomass produced in a sequencing batch reactor process at various times relative to the imposed secondary famine conditions.
- Figure 7 is a graphical illustration of PHA accumulation potential for biomass that has been exposed to secondary famine conditions compared to PHA accumulation potential for a biomass that has only been exposed to primary feast and famine conditions.
- Figure 8 is a pair of graphical illustrations showing PHA accumulation potential after six and 24 hours for two processes, one employing secondary famine conditions and the other only employing primary feast and famine conditions.
- Figure 9 is another graphical illustration showing PHA accumulation potential for two parallel processes, one in which the biomass is subjected to secondary famine conditions and the other involving biomass that is only subjected to primary feast and famine conditions.
- Figure 10 is another graphical illustration showing PHA accumulation potential for parallel processes.
- the methods discussed herein are based on the finding that biomass coming from famine conditions can be stimulated to exhibit an enhancement in its PHA accumulation potential (PAP) by imposing a secondary perturbation to the repeated cycles of the biomass feast and famine during biological water treatment.
- PAP PHA accumulation potential
- such secondary perturbation may be achieved by exposing the biomass or at least a fraction of the biomass to a periodically applied extended period of famine. Such exposure may occur at a given interval in time.
- Exposing the biomass, or fractions of the biomass at a given interval in time, to an extended period of famine has been found to stimulate enhanced PHA storing potential as compared to the same biomass exposed to just the cyclic regime of feast and famine (sometimes referred to as primary feast and famine conditions) without such periodic intervals of an extended famine.
- This additional periodically applied period of famine is called a secondary perturbation to the biomass.
- the primary perturbation to the biomass is the feast and famine cyclic regime.
- the secondary perturbation of additional periodic starvation imposed on the biomass over and above the routine regime of famine serves to condition the biomass in order to increase its potential for PHA storage before entering the accumulation stage of the process.
- the biomass In the accumulation stage, in order to extract the highest value from biomass harvested from a biological treatment system, the biomass accumulates PHA preferably to a level near its full expressed potential.
- the stimulation of an enhanced PAP facilitates greater volumetric productivity during the accumulation process and increases the economy of the PHA recovery from the biomass, since a greater level of PHA accumulation is expressed by the biomass for the same accumulation process.
- the PHA storage response in activated sludge treating water is triggered by availability of RBCOD during feast conditions.
- some contaminated water may have high fractions of RBCOD over total COD
- other untreated waters such as for instance municipal wastewaters, are often with lower fractions of RBCOD over total COD.
- Lower fractions of RBCOD may reduce the ability to produce a biomass with PAP in excess of 50% g-PHA/g-VSS.
- the methods described in this disclosure are of further and particular interest when operating a process for biomass production with PAP using wastewaters with low or moderate fractions of RBCOD over total COD.
- the secondary perturbation can be carried out in different ways. Without limitation, several illustrative examples of embodiments are disclosed below in which a biomass or fractions of a biomass from a process may be subjected to an extended starvation period in batch mode, semi-continuous mode, and continuous mode. Two experimental examples illustrate the batch mode (Example 1) and continuous mode (Example 2) embodiments. It is noted that in some embodiments, a secondary perturbation of famine may be applied after the biomass is subjected to at least two cycles of feast-famine.
- a method or process where a biomass is subjected to repeated cycles of feast and famine wherein the biomass, or fractions of the process biomass, is subjected to a period of extended famine such that:
- the period of extended famine for the biomass or fractions of the biomass at any given time is less than or equal to 1 solids retention time (SRT),
- the length of a secondary (famine) perturbation for the biomass or fractions of the biomass is statistically greater than the average famine period in primary feast-famine cycles and at least equal to the average primary feast-famine period, and
- the given interval in time between repeated secondary perturbation events may vary for the biomass, or fractions of the biomass at any given time, but it is at least as frequently as once every 4 SRTs.
- the SRT is the total mass inventory of biomass divided by the average mass flux of biomass exported from the process.
- SRTs of between 2 to 6 days are often applied.
- a practical operational limit for the length of the period of extended famine for the biomass or fractions of the biomass at any given time is less than or equal to 6 days.
- the method is carried out under a batch operation mode.
- the process biomass that has been enriched under feast and famine conditions is subjected as a whole to an extended phase of famine.
- This extended famine phase may be brought about by preventing organic substrate from being supplied to the biomass during this period.
- An example of such a process is demonstrated in Example 1 , below.
- Figure 1 depicts another embodiment of the method. This embodiment is carried out under continuous or semi-continuous operating conditions rather than in the batch operation mode described in Example 1 .
- the secondary perturbation imposed on the biomass ocurrs in a separate reactor. Not all the biomass is exposed to the secondary perturbation at the same time. However, on average, substantially all the microorganisms in the biomass see a similar periodicity and duration of secondary perturbation.
- the reactor where the secondary perturbation is carried out is placed in a sidestream line separated from a mainstream water treatment line.
- the perturbation reactor (B2, sometimes referred to as a secondary famine reactor) is connected to the mainstream reactor, in this case an SBR (B1).
- SBR SBR
- the biomass in reactor (B1) is in the phase of famine at the time of biomass being pumped to the second reactor (B2) from B1 .
- the retention time of the biomass in the second reactor (B2) is controlled so as to cause a secondary perturbation on the biomass. This stimulates an enhancement in the PAP of the biomass when compared to PAP of the biomass without benefit of reactor (B2) but with the same feast and famine regime that is established by the operation of reactor (B1 ).
- the secondary perturbation reactor (B2) is operating semi-continuously mutually with a mainstream SBR.
- the operation sequence of an SBR cycle may be as follows:
- Wastewater is fed to the reactor (B1).
- Feast conditions are imposed to the biomass in (B1). Feast may be with aerobic, anoxic, or anaerobic conditions maintained.
- mixed liqour is pumped from the mainstream reactor (B1) to the secondary perturbation reactor (B2).
- the primary feast and famine conditions selects a biomass with PHA accumulation potential (PAP) and is carried out in a mainstream biological treatment reactor (such as, for example, an SBR).
- PAP PHA accumulation potential
- the average duration for the secondary perturbation is controlled by the volumes and interval of exchange of mixed liquor containing biomass to and from the main and sidestream reactors.
- the biomass SRT in the overall process is controlled by exporting (harvesting) biomass from the mainstream and/or the sidestream reactors.
- Harvested biomass may be directed to an accumulation process.
- the average retention time (representing the period of secondary famine) of the biomass in the sidestream reactor is longer than the average famine duration in the mainstream reactor but shorter than the SRT of the biomass in the overall process.
- the secondary famine or perturbation conditions for the biomass are such that when the harvested biomass is made to accumulate PHA, the PAP is higher compared to a biomass that is operating under the same regime of feast and famine in reactor (B1) and exclusive of reactor (B2) and any other form of secondary perturbation.
- primary feast and famine conditions are carried out under a continuous flow wastewater treatment process design.
- reactors in series are employed so that feast conditions are carried out in a feast reactor (B1) followed by a primary famine reactor (B2).
- a sequencing batch reactor such as the one disclosed in Figure 1
- reactors in series are employed so that feast conditions are carried out in a feast reactor (B1) followed by a primary famine reactor (B2).
- a system that may be utilized with such an embodiment is shown in Figure 2.
- the secondary famine conditions are carried out by moving biomass from the primary famine reactor (B2) to the secondary famine reactor (B3) that is located in a sidestream relative to the feast reactor (B1 ) and the primary famine reactor (B2).
- secondary famine treatment may be achieved off the return activated sludge line that leads biomass separated from a clarifier after primary famine back to primary feast located upstream in the mainstream.
- primary famine may be initiated in the mainstream and completed in a sidestream reactor that is integrated with the return activated sludge line.
- the primary famine reactor volume providing the time of exposure to primary famine conditions may be split between the mainstream and sidestream.
- the secondary famine reactor can be located off the sidestream primary famine reactor or off the return activated sludge line.
- reactors B1 and B2 may be established as part of a single or multipile of reactor volumes that create for more plug flow hydraulic conditions.
- times of primary feast and primary famine may be delineated by the process hydraulic conditions and the time those hydaulic conditions provide for periods of high (feast) and relatively low (famine) respiration rates for the biomass.
- the process hydraulics and the time those hydraulic conditions provide for an intermittent period of extended (secondary) famine establish the effect of a secondary perturbation for reaching an enhanced PAP.
- Influent RBCOD containing water is used to stimulate the biomass to primary feast conditions.
- a downstream famine reactor or zone establishes primary famine conditions due to consumption of RBCOD in the feast reactor.
- Fractions of the biomass at any given time are moved from conditions of primary famine to conditions of a secondary famine (or secondary perturbation) by virtue of periodically being exposed to prolonged starvation conditions.
- Biomass after being disposed to a secondary perturbation of famine can be moved back to conditions of cyclic primary feast and famine conditions.
- the retention time of the biomass in conditions of secondary perturbation is on average longer than the duration of famine in the mainstream (and or sidestream) but shorter than the overall biomass SRT in the process.
- Secondary perturbation conditions for the biomass are such that when the biomass is made to accumulate PHA, the PAP is higher compared to biomass in the same process that has only been exposed to the primary feast and famine perturbation.
- Municipal wastewater typically contains levels of nitrogen that are in excess of biomass requirements for growth based on the influent organic matter. Therefore, nitrification and denitrification unit processes are frequently integrated to organic carbon removal in the bioprocess design for municipal wastewater treatment.
- some embodiments of the present invention allow for treatment of wastewater and production of biomass with PAP under feast and famine conditions with secondary perturbation, as well as meeting water quality objectives of nitrogen removal. That is, removal of organic matter, as well as nitrogen, from the wastewater is achieved with the added value of harvesting a biomass with enhanced PAP.
- Figure 5 shows a process for producing a PAP-enriched biomass with secondary famine or perturbation in combination with a nitrogen removal process.
- reactor (B1) and reactor (B3) Both are mixed by means of mechanical agitation.
- Denitrification (DN) is performed in reactor (B1).
- primary perturbation that is primary feast and primary famine conditions are maintained in reactor (B1 ) and reactor (B2), respectively.
- Secondary famine or perturbation is carried out in a secondary famine reactor (B3).
- reactor (B1) and reactor (B3) may be maintained under aerobic conditions.
- influent wastewater preferably after some form of primary treatment, is directed to a first reactor (B1 ) where the biomass is stimulated into feast by the influent RBCOD and under anoxic conditions (i.e. with nitrate or nitrite as electron acceptor). Thereafter, the mixed liquor is directed to an aerated reactor (B2) in which nitrification ensues.
- B1 a first reactor
- anoxic conditions i.e. with nitrate or nitrite as electron acceptor
- Nitrification activity may be sustained by populations of nitrifying microorganisms in the suspended solids.
- the populations of nitrifying microorganisms may be more robustly maintained by the application of an integrated biofilm activated sludge (IFAS) unit process design.
- IFAS integrated biofilm activated sludge
- the biofilm biomass may, due to distinctions in retention time, serve to facilitate ammonia-nitrogen removal and/or non-RBCOD degradation.
- An example of an IFAS process that may be used with the methods described herein is one where an activated sludge is integrated with a moving bed biofilm reactor (MBBR) biofilm process, such as the HybasTM process from AnoxKaldnes, headquartered in Lund, Sweden.
- MBBR moving bed biofilm reactor
- the SRT for the purposes of considering secondary perturbation is the SRT based on just the biomass fraction represented by the suspended solids in the process.
- the populations of heterotrophic bacteria in the activated sludge biomass coming from the anoxic feast reactor (B1) will be subjected to famine conditions due to a lack of RBCOD.
- a portion of mixed liquor is recirculated from (B2) to (B1) in order to make nitrate available for the anoxic feast conditions imposed in (B1). Therefore, the recirculation of mixed liquor between (B1 ) and (B2) plays a part in creating feast and primary famine conditions in reactors (B1) and (B2).
- Reactor (B3) provides for secondary perturbation of periodic extended famine of the heterotrophic bacteria in the biomass.
- a prolonged period of famine is introduced in (B3) over and above the regime of routine or primary famine experienced by the biomass in (B2).
- secondary perturbation is applied under anoxic conditions with nitrate or nitrite as the electron acceptor.
- the secondary perturbation therefore, serves simultaneously as a post-denitrification stage for nitrogen effluent water quality management. Since no additional RBCOD is supplied to this stage, the post-den itrification is intended to be driven by endogenous respiration in the biomass.
- the return activated sludge may be directed to either reactor (B1) or reactor (B2).
- control of the primary feast-famine cycle lengths and the length and frequency of secondary perturbation may be made by selecting the fraction of the return activated sludge directed to (B1 ) or (B2), as well as by adjusting the internal recirculation flow between (B1) and (B2).
- Biomass from secondary perturbation is recycled to the primary famine and/or feast reactor.
- the average retention time of the biomass in the secondary perturbation reactor is longer than the average duration of famine in the mainstream but shorter than the global SRT for the suspended solids in the system.
- Secondary perturbation conditions for the biomass are such that, when the biomass is made to accumulate PHA, the PAP is enhanced compared to a biomass produced on the same primary feast-famine perturbation exclusive of any form of secondary perturbation.
- prefered embodiments are such that: • The average flow rate of biomass from the clarifier to (B1) or (B2) is between 0.2 and 2 times the average flow rate of influent wastewater to the process.
- the average flow rate of mixed liquor from (B2) to (B1) is between 1 and 5 times the average flow rate of influent wastewater to the process.
- a process according to the preferred embodiment was carried out in laboratory scale systems.
- Municipal wastewater was treated by activated sludge.
- the biomass was produced under operating conditions of feast and famine in order to enrich for PHA-storage potential, as has been previously disclosed (WO 2012/0231 14A1 ).
- the activated sludge treatment was in two 4 L sequencing batch reactors (SBRs) operating in parallel.
- SBRs sequencing batch reactors
- the SBRs were fed with domestic wastewater obtained directly from a sewer system that serves 150 European communities.
- the sewer delivers 1 .7 million m 3 /day of raw, untreated, domestic wastewater.
- the domestic wastewater drawn from the sewer was filtered (primary treatment) in order to remove suspended solids before being biologically treated in the SBRs.
- the primary treated wastewater composition was on average 748 mg-COD/L of total COD, 196 mg-COD/L of soluble COD, 32.2 mg-N/L of total soluble nitrogen, and 3.31 mg-P/L of total soluble phosphorus.
- SBR-A activated sludge from the Brussels North full-scale wastewater treatment plant and operated according to the conditions described below.
- SBR-B the SBR was duplicated by seeding the biomass produced from SBR-A into a second identical SBR (SBR-B). This seeding was conducted by continuously collecting the excess activated sludge produced twice per day in SBR-A over the course of 4 days and storing the biomass at 4°C.
- the biomass from SBR-A was well-mixed with the biomass stored in the refrigerator and then divided equally between the two SBRs (SBR-A and SBR-B) as a means to ensure identical initial conditions of biomass history for the planned experiment with SBRs A and B.
- SBR-A was the experimental control.
- the operating conditions of SBRs A and B were identical except for one period when all the biomass of SBR-B was subjected to a secondary perturbation in the form of a prolonged famine lasting for four days. During this secondary perturbation of extended famine the biomass was maintained with only mixing and aeration.
- Each operating feast-famine cycle comprised rapidly feeding the SBRs with 3 L of primary treated domestic wastewater for feast stimulation (over a 10 min period) and then aerating for 40 min to reach conditions of famine.
- 50 ml of mixed liquor was wasted in 1 minute (waste activated sludge production).
- the total hydraulic retention time (HRT) was 1 .8 h, whereby the HRT with respect to aerobic conditions was 0.9 h.
- the sludge retention time (SRT) was 1 .8 days, while the aerobic SRT was 0.9 days. SRT takes into account waste sludge production and suspended solids lost in the effluent discharge.
- PHA accumulation potential (PAP) in the activated sludge biomass was assessed according to a reference method. Biomass grab samples were harvested from the SBRs at the end of famine just before the settling stage, transferred to batch reactors, and diluted with tap water to nominally 0.5 g-VSS/L. Two well-mixed 10 L fed batch reactors were operated in parallel aerobically for 24 hours at 20°C with 4 L mixed liquor volumes. Standardized feeding was used for all batch experiments. Feeding for PHA accumulation was achieved by two pulse- additions of a concentrated sodium acetate solution, each providing an increase in acetate concentration in the reactor of 1 g-COD/L.
- PAP t the PHA accumulation Potential referenced to t-hours of accumulation
- a 0 an empirical constant estimating initial PHA content or PAP 0
- a e an empirical constant of the extrapolated PHA accumulation capacity
- k a rate constant (h ⁇ 1 ) estimating the rate of the PHA accumulation
- the removal of influent COD was on average 70 % throughout the operation period. Approximately 88 % of the influent soluble COD (SCOD) was consumed during the feast period.
- the combination of a low feast to the aerobic (feast-famine) time ratio and a high fraction of SCOD consumed during feast were indicators of a good, stable (primary) feast and famine selection pressure and response of the SBR biomass.
- the PHA accumulation potential of the activated sludge in SBR-A increased substantially over the course of the reactor operation.
- the original activated sludge used to inoculate the reactor exhibited a PAP 24 of about 9 % (g- PHA/g-VSS).
- the biomass PAP 6 and PAP 24 were about 20 % and 47 % g-PHA/g-VSS, respectively.
- This range of PAP was sustained in 5 replicate assessments over the 140 days of operation with PAP 6 between 13 and 26 % and PAP 24 between 31 and 47 % g-PHA/g-VSS.
- SBR-B SBR-B
- SBR-A was continuously operated under the same conditions as before.
- SBR-B was subjected to a famine perturbation of four days. After this perturbation, normal SBR operating conditions were resumed.
- SBR-A was continuously operated as before with just the primary feast-famine perturbation, making SBR-A an experimental control.
- SBRs Two laboratory scale sequencing batch reactors
- One of the SBRs was connected to a secondary famine reactor (sometimes the secondary famine reactor is referred to as a secondary perturbation reactor) in which famine was imposed on at least a portion of the biomass as part of the operational cycle of the system.
- secondary famine reactor sometimes the secondary famine reactor is referred to as a secondary perturbation reactor
- significantly enhanced potential to accumulate PHA was generated compared to the control reactor, which was operated with the same primary (feast-famine) perturbation but without any secondary perturbation.
- a process according to a preferred embodiment was carried out in laboratory scale activated sludge systems. Two SBRs were operated in parallel under operating conditions of primary (feast and famine) perturbation in order to enrich the biomass for PHA-accumulation potential (PAP). The conditions were similar to the ones used in Example 1 and the same source of municipal wastewater was employed.
- SBR-A SBR-A
- SBR-(B1) SBR-(B1)
- B2 sidestream secondary perturbation reactor
- the secondary perturbation reactor had a working volume 1 .8 L.
- Both SBR-A and SBR-(B1 ) were closely monitored by means of on-line measurements with dissolved oxygen and pH probes.
- the biomass in SBR-(B1 ) was aerated and stirred at all stages except settling and decanting.
- the reactor (B2) was aerated and stirred at all stages. After decanting the treated wastewater, 1 .5 L of mixed liquor was left in the SBR-(B1) before starting the next cycle of 18 cycles per day. These operating conditions resulted in a HRT of 16 h in reactor (B2).
- SBR-A The experimental control SBR (SBR-A) was operated in an identical cycle as SBR-(B1 ) but without any secondary perturbation reactor. Thus, stages 4 and 5 were omitted in SBR-A. Further, 77 mL of WAS was harvested from SBR-A after famine at every cycle. Consequently, SBR-A was operated under the same volumetric organic loading rate as SBR-(B1). The same solids retention time, based on WAS withdrawal, (4.3 - 4.8 days) was targeted for the biomass in SBR-A as the biomass in SBR-(B1) with (B2).
- the reactors were inoculated by a mixture (50:50 vol-%) of activated sludge from the Brussels North full-scale wastewater treatment plant and activated sludge from a previous laboratory investigation where a mixture of domestic wastewater and a wet-oxidation liquid had been previously used to feed an SBR operated under feast and famine conditions.
- PHA accumulation potential (PAP) in the activated sludge biomass was assessed according to a reference method based on feed-on-demand supply of substrate. Biomass grab samples were harvested from the SBRs at the end of famine just before the settling stage, and then transferred to parallel batch reactors and diluted with tap water to nominally 0.5 g-VSS/L. Two 10 L well-mixed fed batch reactors were operated aerobically for 24-29 hours at 20°C with 4 L mixed liquor volumes. A feed-on-demand strategy was used to dose pulses of nominally 200 mg-COD/L based on the respirometric response of the biomass (WO 201 1 /070544A2). In some experiments, a slightly modified assessment method was used as further detailed below.
- the reference substrate for PHA accumulation was sodium acetate (100 g/L) with limited levels of N and P added to provide a COD:N:P ratio of 100:1 :0.05 (mass basis).
- the accumulation trends were monitored by sampling the fed-batch reactors over time in the same way as in Example 1 .
- the trend of PHA accumulation over time was fit by least squares regression analysis to Equation 1 and the estimated function parameters were used in order to compare the performance in accumulation kinetics and the biomass PAP.
- the concentrations of biomass were, on average, 2.9 and 2.6 g-VSS/L in SBR-A and SBR-(B1 ), respectively.
- the removal of influent COD was on average 51 % and 47 % for SBR- A and SBR-(B1), respectively, with respect to the total COD and 58 % and 53 % with respect to the soluble COD.
- the yield of biomass (0.4 g-VSS per g-SCOD removed) was within the range of values that may be typically observed for an activated sludge process that is operated with a relatively short SRT.
- the PAP of the biomass from the control SBR (SBR-A) and the SBR operated with inclusion of a secondary perturbation reactor (SBR-(B1)) were evaluated twice each using the reference assessment method based on feed-on-demand supply of a solution of synthetic substrate.
- the biomass from the control SBR (SBR-A) was assessed at days 4 and 25 of operation whereas the biomass from SBR-(B1) was assessed at days 10 and 53 of operation.
- the maximum (initial) specific rate of PHA production was similar between SBR-A and SBR-(B1 ) at the same time of operation. However, these rates decreased gradually over SBR operation time from 0.08-0.09 g-PHA/g-X/h before day 10 to 0.03-0.04 g-PHA/g-X/h after day 25. A similar time trend was also observed for the yield of PHA over substrate, decreasing from 0.4 to 0.2 g-PHA/g-Acetate over the course of the SBR operations. These trends in time were likely due to the fact that the SBRs were inoculated, in part, with a biomass that was already well enriched using a more favorable substrate from a wet-oxidation process containing relatively high levels of RBCOD. Thus, developments in the kinetics of accumulation were similar and were understood to be due to the history of biomass and the biomass adaptation to the specific SBR primary perturbation conditions using a municipal wastewater.
- biomass harvested from SBR-A, SBR-(B1 ), and (B2) were assessed for PAP in parallel.
- the biomass samples for these experiments were taken on the same day such that a possible influence in the observed differences between respective biomass PAP performance due to the number of days of enrichment could be controlled for.
- a slightly different assessment method was employed based on standard additions of substrate from a concentrated solution (100 g-Acetate/L with N&P in a COD:N:P ratio of 100:1 :0.05) at the start of the accumulation experiment (1 g-Acetate/L in the accumulation reactor) and after 5 h (0.5 g-Acetate/L), followed by continuous feeding of 200 mL of the substrate solution from 8 to 24 h.
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CN201480013681.3A CN105189369B (en) | 2013-01-11 | 2014-01-10 | Biological wastewater treatment processes that enhances the capacity for polyhydroxyalkanoate accumulation in a mixed culture biomass |
AU2014206079A AU2014206079B2 (en) | 2013-01-11 | 2014-01-10 | Biological wastewater treatment processes that enhances the capacity for polyhydroxyalkanoate accumulation in a mixed culture biomass |
BR112015015646A BR112015015646A2 (en) | 2013-01-11 | 2014-01-10 | method for biologically treating wastewater with biomass and enhancing the potential for biomass polyhydroxyalkanoate (pha) accumulation |
US14/760,221 US9688555B2 (en) | 2013-01-11 | 2014-01-10 | Biological wastewater treatment processes that enhances the capacity for polyhydroxyalkanoate accumulation in a mixed culture biomass |
CA2897369A CA2897369A1 (en) | 2013-01-11 | 2014-01-10 | Biological wastewater treatment processes that enhances the capacity for polyhydroxyalkanoate accumulation in a mixed culture biomass |
EP14701130.8A EP2943443A1 (en) | 2013-01-11 | 2014-01-10 | Biological wastewater treatment processes that enhances the capacity for polyhydroxyalkanoate accumulation in a mixed culture biomass |
KR1020157018439A KR20150093810A (en) | 2013-01-11 | 2014-01-10 | Biological wastewater treatment processes that enhances the capacity for polyhydroxyalkanoate accumulation in a mixed culture biomass |
JP2015552182A JP6125043B2 (en) | 2013-01-11 | 2014-01-10 | Biological wastewater treatment process improves polyhydroxyalkanoate accumulation capacity in mixed culture biomass |
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KR20170005840A (en) | 2014-05-26 | 2017-01-16 | 파크 아이.피. 비.브이. | Process for producing a microbial storage compound |
EP3176132A1 (en) | 2015-12-03 | 2017-06-07 | Paques I.P. B.V. | Process for producing a microbial storage compound |
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CN111762876B (en) * | 2020-07-13 | 2021-11-16 | 南京大学 | Method and device for removing organic micropollutants in water |
CN114988576B (en) * | 2022-06-24 | 2023-03-31 | 北京工业大学 | Method for rapidly realizing short-cut denitrification by taking domestic sewage as carbon source through anoxic starvation |
CN115536128A (en) * | 2022-10-09 | 2022-12-30 | 北京工业大学 | Method for promoting enrichment of PHA accumulation flora in renewable wastewater |
CN115611416A (en) * | 2022-10-11 | 2023-01-17 | 哈尔滨工业大学 | Method for rapidly enriching aerobic denitrifying bacteria based on PHA (polyhydroxyalkanoate) synthesis process by mixed flora |
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EP3176132A1 (en) | 2015-12-03 | 2017-06-07 | Paques I.P. B.V. | Process for producing a microbial storage compound |
EP3760591A1 (en) | 2015-12-03 | 2021-01-06 | Paques I.P. B.V. | Process for producing a microbial storage compound |
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EP2943443A1 (en) | 2015-11-18 |
CN105189369B (en) | 2017-05-03 |
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US9688555B2 (en) | 2017-06-27 |
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