This paper analyses factors associated with bulking in 195 small scale wastewater treatment plant... more This paper analyses factors associated with bulking in 195 small scale wastewater treatment plants (WWTPs) in Estonia. Operational data from each plant were collected and analysed statistically. The key factors associated with bulking were infiltration into sewage pipes, the type and purpose of process reactor, operational practices and influent characteristics. Both anaerobic fraction and volumetric fraction of the anaerobic reactor compared to the aerobic reactor resulted in a positive correlation with sludge volume index (SVI) <150 ml/g values. Good operation and maintenance practice as well as an operator's competence play a crucial role in bulking prevention. Using the 30 minute settling test (V30) as the single process control parameter can mislead an operator's judgement in process control strategies and cause effluent violations. Misjudgements in process control decisions can lead to unwanted conditions in small WWTPs (e.g. excessive chemical addition favoured bul...
Proceedings of the Estonian Academy of Sciences, 2018
The aim of the current study was to investigate and model particle size dependence of the dissolu... more The aim of the current study was to investigate and model particle size dependence of the dissolution process of Ca(OH) 2 , CaCO 3 , and oil shale ash. In the samples of the self-regulating equilibrium system H 2 O-dissolved CO 2-solid CaCO 3 filtered through a 0.45 μm filter no nanoparticles were detected. The nanoparticles appeared when the pH had been increased to 12.3 and the value of the product of the molar concentrations of the Ca 2+ and OHions reached the value of the solubility product constant K sp. When different amounts of Ca(OH) 2 were added to degassed water, the pH increased and nanoparticles started to appear in the solution containing 0.5 g/L of solid Ca(OH) 2 (pH = 12.3). Up to this value of the pH all particles had dissolved. Due to the better solubility of small particles connected to the rise of the value of the solubility product constant K sp for nanoscale particles, the solubility of Ca(OH) 2 , the concentration of Ca 2+ ions, and the pH increased. The pH of oil shale ash leachate increased with the increasing of the amount of ash, as the quantity of nanoparticles increased in a similar manner as described for the solubility of Ca(OH) 2 .
International Journal of Environmental Science and Technology, 2017
Undiluted reject water from the dewatering of anaerobic sludge with an average total nitrogen con... more Undiluted reject water from the dewatering of anaerobic sludge with an average total nitrogen content of 718 ± 117 mg L -1 (n = 63) was used to start-up autotrophic nitrogen removal in three different pilot-scale (3 m 3 ) deammonification configurations: (1) biofilm; (2) activated sludge sequence batch; and (3) two-staged (nitritation-anammox). Time-and concentration-based aeration control with alternating aerobic/anaerobic phases was applied for all reactor configurations. All reactors were initiated without anammox-specific inoculum, and biofilm was grown onto blank carriers. During the initial start-up period, biological nitrogen removal was found to be inhibited by an excessive free ammonia content ([10 mg-N L -1 ), resulting from the use of high-strength reject water as the process feed. After implementation of free ammonia control by pH adjustment to 6.5-7.5, propagation of the deammonification process was observed with increased nitrogen removal with slight accumulation of NO 3 --N. The highest total nitrogen removal rates were achieved with the single-reactor biofilm-and sludge-based deammonification processes (1.04 and 0.30 kg-N m -3 day -1 , respectively). The critical factors for successful start-up and stable operation of deammonification reactors turned out to be control of pH below 7.5, dissolved oxygen at 0.3-0.8 mg-O 2 L -1 and influent solids values below 1000 nephelometric turbidity units. Microbial analysis demonstrated that highest anammox enrichment was achieved in the biofilm reactor (9.40 9 10 8 copies g -1 total suspended solids). These data demonstrate the potential of an in-situ grown sludge-or biofilm-based concept for the development and propagation of deammonification process.
Communications in agricultural and applied biological sciences, 2012
1. Commun Agric Appl Biol Sci. 2012;77(1):227-30. Sulfatereducing and nitrite-dependent anammox f... more 1. Commun Agric Appl Biol Sci. 2012;77(1):227-30. Sulfatereducing and nitrite-dependent anammox for ammonium removal. Rikmann E, Zekker I, Kroon K, Saluste A, Vabamäe P, Tenno T, Menert A, Loorits L, Tenno T. Institute of Chemistry, University of Tartu, 14a Ravila St., 50411 Tartu, Estonia. PMID: 22558786 [PubMed - indexed for MEDLINE]. Publication Types: Research Support, Non-US Gov't. MeSH Terms. Anaerobiosis; Bacteria/classification; ...
Fusion protein constructs for labeled peptides were generated with the 114 amino acid thioredoxin... more Fusion protein constructs for labeled peptides were generated with the 114 amino acid thioredoxin (TRX), coupled with the incorporation of a histidine tag for affinity purification. Two tandem AhdI sites were designed in the multiple cloning site of the fusion vector according to our novel unidirectional TA cloning methodology named PRESATvector, allowing one-step background-free cloning of DNA fragments. Constructs were designed to incorporate the four residue sequence Ile-Asp-Gly-Arg to generate pure peptides following Factor Xa cleavage of the fusion protein. The system is efficient and cost-effective for isotopic labeling of peptides for heteronuclear NMR studies. Seven peptides of varying length, including pituitary adenylate cyclase activating polypeptide (PACAP), vasoactive intestinal peptide (VIP) and ubiquitin interacting motif (UIM), were expressed using this TRX fusion system to give soluble fusion protein constructs in all cases. Three alternative methods for the preparation of DNA fragments were applied depending on the length of the peptides, such as polymerase chain reaction, chemical synthesis or a 'semi-synthetic method', which is a combination of chemical synthesis and enzymatic extension. The ability easily to construct, express and purify recombinant peptides in a high-throughput manner will be of enormous benefit in areas of biomedical research and drug discovery.
The SrS–H2O–gas system was studied to determine the concentrations of formed particles at equilib... more The SrS–H2O–gas system was studied to determine the concentrations of formed particles at equilibrium state after the dissolution of strontium sulfide in distilled water at 25 °C. The solubility of SrS was experimentally measured at a salt concentration range of 0.125–2.924 mM, and the determined pH was at a range of 10.0–11.6. The concentrations of different sulfide forms were determined spectrometrically, potentiometrically
Recently, distance measurements by pulsed ESR (electron spin resonance) have been obtained using ... more Recently, distance measurements by pulsed ESR (electron spin resonance) have been obtained using pulsed DEER (double electron-electron resonance) and DQC (double quantum coherence) in SDSL (site directed spin labeling) proteins. These methods can observe long range dipole interactions (15-80A). We applied these methods to human ubiquitin proteins. The distance between the 20th and the 35th cysteine was estimated in doubly spin labeled human ubiquitin. Pulsed DEER requires two microwave sources. However, a phase cycle is not usually required in this method. On the other hand, DQC-ESR at X-band ( approximately 9GHz) can acquire a large echo signal by using pulses of short duration and high power, but this method has an ESEEM (electron spin echo envelope modulation) problem. We used a commercial pulsed ESR spectrometer and compared these two methods.
Nitrifying biomass on ring-shaped carriers was modified to nitritating one in a relatively short ... more Nitrifying biomass on ring-shaped carriers was modified to nitritating one in a relatively short period of time (37 days) by limiting the air supply, changing the aeration regime, shortening the hydraulic retention time and increasing free ammonia (FA) concentration in the moving-bed biofilm reactor (MBBR). The most efficient strategy for the development and maintenance of nitritating biofilm was found to be the inhibition of nitrifying activity by higher FA concentrations (up to 6.5 mg/L) in the process. Reject water from sludge treatment from the Tallinn Wastewater Treatment Plant was used as substrate in the MBBR. The performance of high-surfaced biocarriers taken from the nitritating activity MBBR was further studied in batch tests to investigate nitritation and nitrification kinetics with various FA concentrations and temperatures. The maximum nitrite accumulation ratio (96.6%) expressed as the percentage of NO 2 −-N/NOx −-N was achieved for FA concentration of 70 mg/L at 36°C. Under the same conditions the specific nitrite oxidation rate achieved was 30 times lower than the specific nitrite formation rate. It was demonstrated that in the biofilm system, inhibition by FA combined with the optimization of the main control parameters is a good strategy to achieve nitritating activity and suppress nitrification.
A biofilm with high nitrifying efficiency was converted into a nitritating and thereafter a nitri... more A biofilm with high nitrifying efficiency was converted into a nitritating and thereafter a nitritating-anammox biofilm in a moving-bed biofilm reactor at 26.5 (±0.5) • C by means of a combination of intermittent aeration, low dissolved oxygen concentration, low hydraulic retention time, free ammonia and furthermore, also by elevated HCO − 3 concentration. Nitriteoxidizing bacteria (NOB) were more effectively suppressed by an enhanced HCO − 3 concentration range of 1200-2350 mg/L as opposed to free-ammonia-based process control where NOBs recovered from inhibition; the respective total-nitrogen removal rates were 0.3 kg N/(m 3 •d) and 0.2 kg N/(m 3 •d). The biofilm modification strategies resulted in a shift in bacterial community as the NOB Nitrobacter spp. were replaced with NOB belonging to the genus Nitrospira spp. and were closely related to Candidatus Nitrospira defluvii. A community of anaerobic ammonium-oxidizing microorganisms-uncultured Planctomycetales bacterium clone P4 (closely related to Candidatus Brocadia fulgida)-was developed.
The anammox bacteria were enriched from reject water of anaerobic digestion of municipal wastewat... more The anammox bacteria were enriched from reject water of anaerobic digestion of municipal wastewater sludge onto moving bed biofilm reactor (MBBR) system carriers-the ones initially containing no biomass (MBBR1) as well as the ones containing nitrifying biomass (MBBR2). Duration of start-up periods of the both reactors was similar (about 100 days), but stable total nitrogen (TN) removal efficiency occurred earlier in the system containing nitrifying biomass. Anammox TN removal efficiency of 70% was achieved by 180 days in both 20 l volume reactors at moderate temperature of 26.0°C. During the steady state phase of operation of MBBRs the average TN removal efficiencies and maximum TN removal rates in MBBR1 were 80% (1,000 g-N/m(3)/day, achieved by 308 days) and in MBBR2 85% (1,100 g-N/m(3)/day, achieved by 266 days). In both reactors mixed bacterial cultures were detected. Uncultured Planctomycetales bacterium clone P4, Candidatus Nitrospira defluvii and uncultured Nitrospira sp. clone 53 were identified by PCR-DGGE from the system initially containing blank biofilm carriers as well as from the nitrifying biofilm system; from the latter in addition to these also uncultured ammonium oxidizing bacterium clone W1 and Nitrospira sp. clone S1-62 were detected. FISH analysis revealed that anammox microorganisms were located in clusters in the biofilm. Using previously grown nitrifying biofilm matrix for anammox enrichment has some benefits over starting up the process from zero, such as less time for enrichment and protection against severe inhibitions in case of high substrate loading rates.
h i g h l i g h t s Reused ferric sludge as an effective catalyst for the Fenton-based process. O... more h i g h l i g h t s Reused ferric sludge as an effective catalyst for the Fenton-based process. Observed a similar Fenton-based treatment efficacy for up to 4 ferric sludge reuses. Revealed the effective catalytic properties of ferric-sludge without any prior regeneration. Displayed a similar treatment efficiency using dissolved iron or ferric sludge in the catalysed Fenton process.
Research of oxygen mass transfer through the air–water surface at low bulk concentrations of surf... more Research of oxygen mass transfer through the air–water surface at low bulk concentrations of surfactants
Wastewater in industrial regions frequently contains substances which are potentially inhibitory ... more Wastewater in industrial regions frequently contains substances which are potentially inhibitory to activated sludge treatment processes. Enhanced biological phosphorus removal (EBPR) is vulnerable to process inhibition mostly because of the location at the beginning of the treatment process and complex characteristics of influent. Much knowledge has been developed on the EBPR process; nonetheless, methods used for estimation of the process inhibition vary largely. There is no easily applicable and reliable method available for rapid determination of inhibition of the EBPR process. In this study, a method for evaluation of inhibition on the EBPR process was developed and controlled. In contrast with previous research, a fresh non-acclimated inoculum was used to enhance the possibility to predict the impact for wastewater treatment plant. The efficiency of the process was evaluated based on the values of orthophosphate release and uptake, synthesis and consumption of polyhydroxyalkanoates. 3,5-dichlorophenol (3,5-DCP) was used as a model inhibitory compound. It was found that the EBPR inhibition tests using a non-acclimated sludge need wastewater as the organic carbon source. Furthermore, the length of aerobic period substantially influenced the inhibition test resultsachieved maximum inhibitory concentration (IC 50) values were 2.4 times higher when aerobic phase was 6 h instead of 1.5 h. Consequently, extended aeration period was suggested to diminish the inhibition effect. Finally, the impact of the 3,5-DCP on different activated sludge treatment process using respective standard methods was tested and compared. It was found that EBPR process was similarly to the nitrification a sensitive activated sludge process.
For N-rich wastewater treatment the anaerobic ammonium oxidation (anammox) and nitritation-anammo... more For N-rich wastewater treatment the anaerobic ammonium oxidation (anammox) and nitritation-anammox (deammonification) processes are widely used. In a deammonification moving bed biofilm reactor (MBBR) a maximum total nitrogen removal rate (TNRR) of 1.5 g N m-2d-1(0.6 kg N m-3d-1) was achieved. During biofilm cultivation, temperature was gradually lowered by 0.5° C per week, and a similar TNRR was sustained at 15° C. qPCR analysis showed an increase in Candidatus Brocadia quantities from 5×103 to 1×107 anammox gene copies g-1 TSS despite temperature lowered to 15° C. Fluctuations in TNRR were rather related to changes in influent NH4+ concentration. To study the short-term effect of temperature on the TNRR, a series of batch-scale experiments were performed which showed sufficient TNRRs even at 9-15° C (4.3-5.4 mg N L-1 h-1, respectively) with anammox temperature constants ranging 1.3-1.6. After biomass was adapted to 15° C, the decrease in TNRR in batch tests at 9° C was lower (15-2...
Biological nutrient removal from wastewater to reach acceptable levels is needed to protect water... more Biological nutrient removal from wastewater to reach acceptable levels is needed to protect water resources and avoid eutrophication. The start-up of an anaerobic ammonium oxidation (anammox) process from scratch was investigated in a 20 L sequence batch reactor (SBR) inoculated with a mixture of aerobic and anaerobic sludge at 30 ± 0.5 °C with a hydraulic retention time (HRT) of 2–3 days. The use of NH4Cl, NaNO2, and reject water as nitrogen sources created different salinity periods, in which the anammox process performance was assessed: low (<0.2 g of Cl−/L), high (18.2 g of Cl−/L), or optimum salinity (0.5–2 g of Cl−/L). Reject water feeding gave the optimum salinity, with an average nitrogen removal efficiency of 80%, and a TNRR of 0.08 kg N/m3/d being achieved after 193 days. The main aim was to show the effect of a hydrazine addition on the specific anammox activity (SAA) and denitrification activity in the start-up process to boost the autotrophic nitrogen removal from sc...
Lowered air supply and organic carbon need are the key factors to reduce wastewater treatment cos... more Lowered air supply and organic carbon need are the key factors to reduce wastewater treatment costs and thereby, avoid eutrophication. Denitrifying PO43-- removal (DPR) process using nitrate instead of oxygen for PO43- uptake was started up in the sequencing batch reactor (SBR) at a nitrate dosing rate of 20-25 mg N L-1 d-1. Operation with a real municipal wastewater supplied with CH3COONa, K2HPO4 and KNO3 succeeded in the cultivation of biomass containing denitrifying polyphosphate accumulating organisms (DPAOs). The durations of SBR process anaerobic/anoxic/oxic cycles were 1.5 h, 3.5 h and 1 h, respectively. SBR operation resulted in a maximum PO43--P uptake of 17 mg PO43--P g-1 MLSS. The highest TN and PO43- removal efficiencies were observed during the first half of reactor operation at 77 (±10) % and 71 (±5) %, respectively. An average COD removal rate of 172 (±98) mg g-1 MLSS and a high average removal efficiency of 89 (±4) % were achieved. Nitrite effect with/without nitrate as DPR electron acceptor was investigated in batch-scale to show possibilities to use high nitrite and nitrate contents simultaneously as electron acceptors for the anoxic phosphate uptake. Nitrate attenuation against nitrite toxicity can be economically justified in full-scale treatment applications in which wastewater has a high nitrogen content. Nitrate attenuated nitrite toxicity (caused by nitrite content at 5-100 mg NO2--N L-1) when using supplemental additions of nitrate (at concentrations of 45-200 mg NO3--N L-1) in batch tests. Illumina sequencing emphasized that during biomass adaption microbial community changed by lowered aerobic cycle length and by lowered nitrate dosing towards representation of key DPAO/PAO- organisms, such as Candidatus Accumulibacter, Xanthomonadaceae, Comomonadaceae, Saprospiraceae and Rhodocyclaceae. This study showed that DPAO biomass adaption to nitrate maintained an efficient COD, nitrogen and phosphorus removal and the biomass can be applied for treatment of wastewater containing high nitrite and nitrate content.
The inoculum biomass was collected from a pilot-scale (3 m3 process tank) nitritation-anaerobic a... more The inoculum biomass was collected from a pilot-scale (3 m3 process tank) nitritation-anaerobic ammonium oxidation (ANAMMOX) (deammonification moving bed biofilm (DeaMBBR)) reactor demonstrating the highest total nitrogen removal rate (TNRR) of 0.33 kg N m-3 day-1. This biomass was used for inoculating the anodic chamber of a microbial fuel cell (MFC) to investigate the capacity of DeaMBBR biomass to act as an exo-electrogenic consortia. Performance of MFCs inoculated with ANAMMOX-specific consortia collected from DeaMBBR (MFC-ANA) and another MFC-CON inoculated with a septic tank mixed anaerobic consortium as a control was investigated for electrochemical performance and wastewater treatment efficiency. These MFCs were operated for the total duration of 419 days during which regular feed was given and performance was monitored for first 30 cycles and last 30 cycles, with each cycle of 3 day duration. The MFC-ANA continuously generated bio-energy with higher volumetric power density (9.5 W m-3 and 6.0 W m-3) in comparison to MFC-CON (4.9 and 2.9 W m-3) during the first 30 and last 30 cycles of operational period, respectively. MFC-ANA also achieved 84 ± 2% and 80 ± 2% of COD removal efficiency and 89 ± 4% and 73 ± 2% of total nitrogen removal efficiency during first 30 and last 30 cycles of operational period, respectively. The improvement of nitrogen removal and power production in case of MFC-ANA over MFC-CON could be attributed to the ANAMMOX-denitrifiers populations and Trichococcus (14.92%) as denitrifying exo-electrogenic microbes (4.46%), respectively.
This paper analyses factors associated with bulking in 195 small scale wastewater treatment plant... more This paper analyses factors associated with bulking in 195 small scale wastewater treatment plants (WWTPs) in Estonia. Operational data from each plant were collected and analysed statistically. The key factors associated with bulking were infiltration into sewage pipes, the type and purpose of process reactor, operational practices and influent characteristics. Both anaerobic fraction and volumetric fraction of the anaerobic reactor compared to the aerobic reactor resulted in a positive correlation with sludge volume index (SVI) <150 ml/g values. Good operation and maintenance practice as well as an operator's competence play a crucial role in bulking prevention. Using the 30 minute settling test (V30) as the single process control parameter can mislead an operator's judgement in process control strategies and cause effluent violations. Misjudgements in process control decisions can lead to unwanted conditions in small WWTPs (e.g. excessive chemical addition favoured bul...
Proceedings of the Estonian Academy of Sciences, 2018
The aim of the current study was to investigate and model particle size dependence of the dissolu... more The aim of the current study was to investigate and model particle size dependence of the dissolution process of Ca(OH) 2 , CaCO 3 , and oil shale ash. In the samples of the self-regulating equilibrium system H 2 O-dissolved CO 2-solid CaCO 3 filtered through a 0.45 μm filter no nanoparticles were detected. The nanoparticles appeared when the pH had been increased to 12.3 and the value of the product of the molar concentrations of the Ca 2+ and OHions reached the value of the solubility product constant K sp. When different amounts of Ca(OH) 2 were added to degassed water, the pH increased and nanoparticles started to appear in the solution containing 0.5 g/L of solid Ca(OH) 2 (pH = 12.3). Up to this value of the pH all particles had dissolved. Due to the better solubility of small particles connected to the rise of the value of the solubility product constant K sp for nanoscale particles, the solubility of Ca(OH) 2 , the concentration of Ca 2+ ions, and the pH increased. The pH of oil shale ash leachate increased with the increasing of the amount of ash, as the quantity of nanoparticles increased in a similar manner as described for the solubility of Ca(OH) 2 .
International Journal of Environmental Science and Technology, 2017
Undiluted reject water from the dewatering of anaerobic sludge with an average total nitrogen con... more Undiluted reject water from the dewatering of anaerobic sludge with an average total nitrogen content of 718 ± 117 mg L -1 (n = 63) was used to start-up autotrophic nitrogen removal in three different pilot-scale (3 m 3 ) deammonification configurations: (1) biofilm; (2) activated sludge sequence batch; and (3) two-staged (nitritation-anammox). Time-and concentration-based aeration control with alternating aerobic/anaerobic phases was applied for all reactor configurations. All reactors were initiated without anammox-specific inoculum, and biofilm was grown onto blank carriers. During the initial start-up period, biological nitrogen removal was found to be inhibited by an excessive free ammonia content ([10 mg-N L -1 ), resulting from the use of high-strength reject water as the process feed. After implementation of free ammonia control by pH adjustment to 6.5-7.5, propagation of the deammonification process was observed with increased nitrogen removal with slight accumulation of NO 3 --N. The highest total nitrogen removal rates were achieved with the single-reactor biofilm-and sludge-based deammonification processes (1.04 and 0.30 kg-N m -3 day -1 , respectively). The critical factors for successful start-up and stable operation of deammonification reactors turned out to be control of pH below 7.5, dissolved oxygen at 0.3-0.8 mg-O 2 L -1 and influent solids values below 1000 nephelometric turbidity units. Microbial analysis demonstrated that highest anammox enrichment was achieved in the biofilm reactor (9.40 9 10 8 copies g -1 total suspended solids). These data demonstrate the potential of an in-situ grown sludge-or biofilm-based concept for the development and propagation of deammonification process.
Communications in agricultural and applied biological sciences, 2012
1. Commun Agric Appl Biol Sci. 2012;77(1):227-30. Sulfatereducing and nitrite-dependent anammox f... more 1. Commun Agric Appl Biol Sci. 2012;77(1):227-30. Sulfatereducing and nitrite-dependent anammox for ammonium removal. Rikmann E, Zekker I, Kroon K, Saluste A, Vabamäe P, Tenno T, Menert A, Loorits L, Tenno T. Institute of Chemistry, University of Tartu, 14a Ravila St., 50411 Tartu, Estonia. PMID: 22558786 [PubMed - indexed for MEDLINE]. Publication Types: Research Support, Non-US Gov't. MeSH Terms. Anaerobiosis; Bacteria/classification; ...
Fusion protein constructs for labeled peptides were generated with the 114 amino acid thioredoxin... more Fusion protein constructs for labeled peptides were generated with the 114 amino acid thioredoxin (TRX), coupled with the incorporation of a histidine tag for affinity purification. Two tandem AhdI sites were designed in the multiple cloning site of the fusion vector according to our novel unidirectional TA cloning methodology named PRESATvector, allowing one-step background-free cloning of DNA fragments. Constructs were designed to incorporate the four residue sequence Ile-Asp-Gly-Arg to generate pure peptides following Factor Xa cleavage of the fusion protein. The system is efficient and cost-effective for isotopic labeling of peptides for heteronuclear NMR studies. Seven peptides of varying length, including pituitary adenylate cyclase activating polypeptide (PACAP), vasoactive intestinal peptide (VIP) and ubiquitin interacting motif (UIM), were expressed using this TRX fusion system to give soluble fusion protein constructs in all cases. Three alternative methods for the preparation of DNA fragments were applied depending on the length of the peptides, such as polymerase chain reaction, chemical synthesis or a 'semi-synthetic method', which is a combination of chemical synthesis and enzymatic extension. The ability easily to construct, express and purify recombinant peptides in a high-throughput manner will be of enormous benefit in areas of biomedical research and drug discovery.
The SrS–H2O–gas system was studied to determine the concentrations of formed particles at equilib... more The SrS–H2O–gas system was studied to determine the concentrations of formed particles at equilibrium state after the dissolution of strontium sulfide in distilled water at 25 °C. The solubility of SrS was experimentally measured at a salt concentration range of 0.125–2.924 mM, and the determined pH was at a range of 10.0–11.6. The concentrations of different sulfide forms were determined spectrometrically, potentiometrically
Recently, distance measurements by pulsed ESR (electron spin resonance) have been obtained using ... more Recently, distance measurements by pulsed ESR (electron spin resonance) have been obtained using pulsed DEER (double electron-electron resonance) and DQC (double quantum coherence) in SDSL (site directed spin labeling) proteins. These methods can observe long range dipole interactions (15-80A). We applied these methods to human ubiquitin proteins. The distance between the 20th and the 35th cysteine was estimated in doubly spin labeled human ubiquitin. Pulsed DEER requires two microwave sources. However, a phase cycle is not usually required in this method. On the other hand, DQC-ESR at X-band ( approximately 9GHz) can acquire a large echo signal by using pulses of short duration and high power, but this method has an ESEEM (electron spin echo envelope modulation) problem. We used a commercial pulsed ESR spectrometer and compared these two methods.
Nitrifying biomass on ring-shaped carriers was modified to nitritating one in a relatively short ... more Nitrifying biomass on ring-shaped carriers was modified to nitritating one in a relatively short period of time (37 days) by limiting the air supply, changing the aeration regime, shortening the hydraulic retention time and increasing free ammonia (FA) concentration in the moving-bed biofilm reactor (MBBR). The most efficient strategy for the development and maintenance of nitritating biofilm was found to be the inhibition of nitrifying activity by higher FA concentrations (up to 6.5 mg/L) in the process. Reject water from sludge treatment from the Tallinn Wastewater Treatment Plant was used as substrate in the MBBR. The performance of high-surfaced biocarriers taken from the nitritating activity MBBR was further studied in batch tests to investigate nitritation and nitrification kinetics with various FA concentrations and temperatures. The maximum nitrite accumulation ratio (96.6%) expressed as the percentage of NO 2 −-N/NOx −-N was achieved for FA concentration of 70 mg/L at 36°C. Under the same conditions the specific nitrite oxidation rate achieved was 30 times lower than the specific nitrite formation rate. It was demonstrated that in the biofilm system, inhibition by FA combined with the optimization of the main control parameters is a good strategy to achieve nitritating activity and suppress nitrification.
A biofilm with high nitrifying efficiency was converted into a nitritating and thereafter a nitri... more A biofilm with high nitrifying efficiency was converted into a nitritating and thereafter a nitritating-anammox biofilm in a moving-bed biofilm reactor at 26.5 (±0.5) • C by means of a combination of intermittent aeration, low dissolved oxygen concentration, low hydraulic retention time, free ammonia and furthermore, also by elevated HCO − 3 concentration. Nitriteoxidizing bacteria (NOB) were more effectively suppressed by an enhanced HCO − 3 concentration range of 1200-2350 mg/L as opposed to free-ammonia-based process control where NOBs recovered from inhibition; the respective total-nitrogen removal rates were 0.3 kg N/(m 3 •d) and 0.2 kg N/(m 3 •d). The biofilm modification strategies resulted in a shift in bacterial community as the NOB Nitrobacter spp. were replaced with NOB belonging to the genus Nitrospira spp. and were closely related to Candidatus Nitrospira defluvii. A community of anaerobic ammonium-oxidizing microorganisms-uncultured Planctomycetales bacterium clone P4 (closely related to Candidatus Brocadia fulgida)-was developed.
The anammox bacteria were enriched from reject water of anaerobic digestion of municipal wastewat... more The anammox bacteria were enriched from reject water of anaerobic digestion of municipal wastewater sludge onto moving bed biofilm reactor (MBBR) system carriers-the ones initially containing no biomass (MBBR1) as well as the ones containing nitrifying biomass (MBBR2). Duration of start-up periods of the both reactors was similar (about 100 days), but stable total nitrogen (TN) removal efficiency occurred earlier in the system containing nitrifying biomass. Anammox TN removal efficiency of 70% was achieved by 180 days in both 20 l volume reactors at moderate temperature of 26.0°C. During the steady state phase of operation of MBBRs the average TN removal efficiencies and maximum TN removal rates in MBBR1 were 80% (1,000 g-N/m(3)/day, achieved by 308 days) and in MBBR2 85% (1,100 g-N/m(3)/day, achieved by 266 days). In both reactors mixed bacterial cultures were detected. Uncultured Planctomycetales bacterium clone P4, Candidatus Nitrospira defluvii and uncultured Nitrospira sp. clone 53 were identified by PCR-DGGE from the system initially containing blank biofilm carriers as well as from the nitrifying biofilm system; from the latter in addition to these also uncultured ammonium oxidizing bacterium clone W1 and Nitrospira sp. clone S1-62 were detected. FISH analysis revealed that anammox microorganisms were located in clusters in the biofilm. Using previously grown nitrifying biofilm matrix for anammox enrichment has some benefits over starting up the process from zero, such as less time for enrichment and protection against severe inhibitions in case of high substrate loading rates.
h i g h l i g h t s Reused ferric sludge as an effective catalyst for the Fenton-based process. O... more h i g h l i g h t s Reused ferric sludge as an effective catalyst for the Fenton-based process. Observed a similar Fenton-based treatment efficacy for up to 4 ferric sludge reuses. Revealed the effective catalytic properties of ferric-sludge without any prior regeneration. Displayed a similar treatment efficiency using dissolved iron or ferric sludge in the catalysed Fenton process.
Research of oxygen mass transfer through the air–water surface at low bulk concentrations of surf... more Research of oxygen mass transfer through the air–water surface at low bulk concentrations of surfactants
Wastewater in industrial regions frequently contains substances which are potentially inhibitory ... more Wastewater in industrial regions frequently contains substances which are potentially inhibitory to activated sludge treatment processes. Enhanced biological phosphorus removal (EBPR) is vulnerable to process inhibition mostly because of the location at the beginning of the treatment process and complex characteristics of influent. Much knowledge has been developed on the EBPR process; nonetheless, methods used for estimation of the process inhibition vary largely. There is no easily applicable and reliable method available for rapid determination of inhibition of the EBPR process. In this study, a method for evaluation of inhibition on the EBPR process was developed and controlled. In contrast with previous research, a fresh non-acclimated inoculum was used to enhance the possibility to predict the impact for wastewater treatment plant. The efficiency of the process was evaluated based on the values of orthophosphate release and uptake, synthesis and consumption of polyhydroxyalkanoates. 3,5-dichlorophenol (3,5-DCP) was used as a model inhibitory compound. It was found that the EBPR inhibition tests using a non-acclimated sludge need wastewater as the organic carbon source. Furthermore, the length of aerobic period substantially influenced the inhibition test resultsachieved maximum inhibitory concentration (IC 50) values were 2.4 times higher when aerobic phase was 6 h instead of 1.5 h. Consequently, extended aeration period was suggested to diminish the inhibition effect. Finally, the impact of the 3,5-DCP on different activated sludge treatment process using respective standard methods was tested and compared. It was found that EBPR process was similarly to the nitrification a sensitive activated sludge process.
For N-rich wastewater treatment the anaerobic ammonium oxidation (anammox) and nitritation-anammo... more For N-rich wastewater treatment the anaerobic ammonium oxidation (anammox) and nitritation-anammox (deammonification) processes are widely used. In a deammonification moving bed biofilm reactor (MBBR) a maximum total nitrogen removal rate (TNRR) of 1.5 g N m-2d-1(0.6 kg N m-3d-1) was achieved. During biofilm cultivation, temperature was gradually lowered by 0.5° C per week, and a similar TNRR was sustained at 15° C. qPCR analysis showed an increase in Candidatus Brocadia quantities from 5×103 to 1×107 anammox gene copies g-1 TSS despite temperature lowered to 15° C. Fluctuations in TNRR were rather related to changes in influent NH4+ concentration. To study the short-term effect of temperature on the TNRR, a series of batch-scale experiments were performed which showed sufficient TNRRs even at 9-15° C (4.3-5.4 mg N L-1 h-1, respectively) with anammox temperature constants ranging 1.3-1.6. After biomass was adapted to 15° C, the decrease in TNRR in batch tests at 9° C was lower (15-2...
Biological nutrient removal from wastewater to reach acceptable levels is needed to protect water... more Biological nutrient removal from wastewater to reach acceptable levels is needed to protect water resources and avoid eutrophication. The start-up of an anaerobic ammonium oxidation (anammox) process from scratch was investigated in a 20 L sequence batch reactor (SBR) inoculated with a mixture of aerobic and anaerobic sludge at 30 ± 0.5 °C with a hydraulic retention time (HRT) of 2–3 days. The use of NH4Cl, NaNO2, and reject water as nitrogen sources created different salinity periods, in which the anammox process performance was assessed: low (<0.2 g of Cl−/L), high (18.2 g of Cl−/L), or optimum salinity (0.5–2 g of Cl−/L). Reject water feeding gave the optimum salinity, with an average nitrogen removal efficiency of 80%, and a TNRR of 0.08 kg N/m3/d being achieved after 193 days. The main aim was to show the effect of a hydrazine addition on the specific anammox activity (SAA) and denitrification activity in the start-up process to boost the autotrophic nitrogen removal from sc...
Lowered air supply and organic carbon need are the key factors to reduce wastewater treatment cos... more Lowered air supply and organic carbon need are the key factors to reduce wastewater treatment costs and thereby, avoid eutrophication. Denitrifying PO43-- removal (DPR) process using nitrate instead of oxygen for PO43- uptake was started up in the sequencing batch reactor (SBR) at a nitrate dosing rate of 20-25 mg N L-1 d-1. Operation with a real municipal wastewater supplied with CH3COONa, K2HPO4 and KNO3 succeeded in the cultivation of biomass containing denitrifying polyphosphate accumulating organisms (DPAOs). The durations of SBR process anaerobic/anoxic/oxic cycles were 1.5 h, 3.5 h and 1 h, respectively. SBR operation resulted in a maximum PO43--P uptake of 17 mg PO43--P g-1 MLSS. The highest TN and PO43- removal efficiencies were observed during the first half of reactor operation at 77 (±10) % and 71 (±5) %, respectively. An average COD removal rate of 172 (±98) mg g-1 MLSS and a high average removal efficiency of 89 (±4) % were achieved. Nitrite effect with/without nitrate as DPR electron acceptor was investigated in batch-scale to show possibilities to use high nitrite and nitrate contents simultaneously as electron acceptors for the anoxic phosphate uptake. Nitrate attenuation against nitrite toxicity can be economically justified in full-scale treatment applications in which wastewater has a high nitrogen content. Nitrate attenuated nitrite toxicity (caused by nitrite content at 5-100 mg NO2--N L-1) when using supplemental additions of nitrate (at concentrations of 45-200 mg NO3--N L-1) in batch tests. Illumina sequencing emphasized that during biomass adaption microbial community changed by lowered aerobic cycle length and by lowered nitrate dosing towards representation of key DPAO/PAO- organisms, such as Candidatus Accumulibacter, Xanthomonadaceae, Comomonadaceae, Saprospiraceae and Rhodocyclaceae. This study showed that DPAO biomass adaption to nitrate maintained an efficient COD, nitrogen and phosphorus removal and the biomass can be applied for treatment of wastewater containing high nitrite and nitrate content.
The inoculum biomass was collected from a pilot-scale (3 m3 process tank) nitritation-anaerobic a... more The inoculum biomass was collected from a pilot-scale (3 m3 process tank) nitritation-anaerobic ammonium oxidation (ANAMMOX) (deammonification moving bed biofilm (DeaMBBR)) reactor demonstrating the highest total nitrogen removal rate (TNRR) of 0.33 kg N m-3 day-1. This biomass was used for inoculating the anodic chamber of a microbial fuel cell (MFC) to investigate the capacity of DeaMBBR biomass to act as an exo-electrogenic consortia. Performance of MFCs inoculated with ANAMMOX-specific consortia collected from DeaMBBR (MFC-ANA) and another MFC-CON inoculated with a septic tank mixed anaerobic consortium as a control was investigated for electrochemical performance and wastewater treatment efficiency. These MFCs were operated for the total duration of 419 days during which regular feed was given and performance was monitored for first 30 cycles and last 30 cycles, with each cycle of 3 day duration. The MFC-ANA continuously generated bio-energy with higher volumetric power density (9.5 W m-3 and 6.0 W m-3) in comparison to MFC-CON (4.9 and 2.9 W m-3) during the first 30 and last 30 cycles of operational period, respectively. MFC-ANA also achieved 84 ± 2% and 80 ± 2% of COD removal efficiency and 89 ± 4% and 73 ± 2% of total nitrogen removal efficiency during first 30 and last 30 cycles of operational period, respectively. The improvement of nitrogen removal and power production in case of MFC-ANA over MFC-CON could be attributed to the ANAMMOX-denitrifiers populations and Trichococcus (14.92%) as denitrifying exo-electrogenic microbes (4.46%), respectively.
Uploads
Papers by Taavo Tenno