Nutrient removal from slaughterhouse wastewater in an intermittently aerated sequencing batch reactor

The performance of a 10 L sequencing batch reactor (SBR) treating slaughterhouse wastewater was examined at ambient temperature. The influent wastewater comprised 4672+/-952 mg chemical oxygen demand (COD)/L, 356+/-46 mg total nitrogen (TN)/L and 29+/-10 mg total phosphorus (TP)/L. The duration of a complete cycle was 8 h and comprised four phases: fill (7 min), react (393 min), settle (30 min) and draw/idle (50 min). During the react phase, the reactor was intermittently aerated with an air supply of 0.8L/min four times at 50-min intervals, 50 min each time. At an influent organic loading rate of 1.2g COD/(Ld), average effluent concentrations of COD, TN and TP were 150 mg/L, 15 mg/L and 0.8 mg/L, respectively. This represented COD, TN and TP removals of 96%, 96% and 99%, respectively. Phase studies show that biological phosphorus uptake occurred in the first aeration period and nitrogen removal took place in the following reaction time by means of partial nitrification and denitrification. The nitrogen balance analysis indicates that denitrification and biomass synthesis contributed to 66% and 34% of TN removed, respectively.     

Anammox enrichment from reject water on blank biofilm carriers and carriers containing nitrifying biomass: operation of two moving bed biofilm reactors (MBBR)

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.     

Evaluation of support materials for the immobilization of sulfate-reducing bacteria and methanogenic archaea

This paper reports on the adhesion of sulfate-reducing bacteria (SRB) and methanogenic archaea on polyurethane foam (PU), vegetal carbon (VC), low-density polyethylene (PE) and alumina-based ceramics (CE). Anaerobic differential reactors fed with a sulfate-rich synthetic wastewater were used to evaluate the formation of a biofilm. The PU presented the highest specific biomass concentration throughout the experiment, achieving 872 mg TVS/g support, while 84 mg TVS/g support was the maximum value obtained for the other materials. FISH results showed that bacterial cells rather than archaeal cells were predominant on the biofilms. These cells, detected with EUB338 probe, accounted for 76.2% (+/-1.6%), 79.7% (+/-1.3%), 84.4% (+/-1.4%) and 60.2% (+/-1.0%) in PU, VC, PE and CE, respectively, of the 4'6-diamidino-2-phenylindole (DAPI)-stained cells. From these percentages, 44.8% (+/-2.1%), 55.4% (+/-1.2%), 32.7% (+/-1.4%) and 18.1% (+/-1.1%), respectively, represented the SRB group. Archaeal cells, detected with ARC915 probe, accounted for 33.1% (+/-1.6%), 25.4% (+/-1.3%), 22.6% (+/-1.1%) and 41.9% (+/-1.0%) in PU, VC, PE and CE, respectively, of the DAPI-stained cells. Sulfate reduction efficiencies of 39% and 45% and mean chemical oxygen demand (COD) removal efficiencies of 86% and 90% were achieved for PU and VC, respectively. The other two supports, PE and CE, provided mean COD removal efficiencies of 84% and 86%, respectively. However, no sulfate reduction was observed with these supports.     

Batch biological treatment of nitrogen deficient synthetic wastewater using Azotobacter supplemented activated sludge

Biological treatment of nitrogen deficient wastewaters are usually accomplished by external addition of nitrogen sources to the wastewater which is an extra cost item. As an alternative for effective biological treatment of nitrogen deficient wastewaters, the nitrogen fixing bacterium, Azotobacter vinelandii, was used in activated sludge and also in pure culture. Total organic carbon (TOC) removal performances of Azotobacter-added and free activated sludge cultures were compared at different initial TN/TOC ratios. The rate and extent of TOC removal were comparable for all cultures when initial TN/TOC ratio was larger than 0.12; however, both the rate and extent of TOC removal from nitrogen deficient (TN/TOC<12%) synthetic wastewater were improved by using Azotobacter-added activated sludge as compared to the Azotobacter-free activated sludge culture. More than 90% TOC removal was obtained with pure Azotobacter or Azotobacter-added activated sludge culture from a nitrogen deficient synthetic wastewater.     

Bioremoval of Aqueous Lead Using Lemna Minor

The aquatic plant Lemna minor (duckweed) was examined for its ability to sorb soluble lead from water under laboratory conditions. The use of biomass as a sorption medium provides a simple alternative separation technology. Laboratory-scale (700-mL) batch reactors containing soil-based sediments were used to expose L. minor to concentrations of 0.0, 5.0, and 10.0 mg/L of lead for 7 d. Overall removal amounts of 95% were observed, with 85% removal occurring within the first day. A sorption process model was developed based on a mass balance and a power law rate of sorption equation.     

Performance and Microbial Structure of a Combined Biofilm Reactor

A novel combined biofilm reactor was established and applied as a single treatment unit for carbon and nitrogen removal of wastewater. The nitrogen removal performance of the reactor at different levels of organic carbon (COD) loading was investigated when the influent total nitrogen (TN) loading was 0.74 g TN/m² day. Continuous experimental results demonstrated that 80% nitrogen was eliminated when the influent COD loading ranged between 2.06 g and 3.92 g COD/m² day. Microbial composition in the reactor was analyzed using fluorescent in situ hybridization (FISH) and conventional batch tests. The relative abundance of ammonia-oxidizing bacteria in the aerobic zone of the reactor measured by FISH was consistent with the result from conventional batch tests.     

Immobilized white-rot fungal biodegradation of phenol and chlorinated phenol in trickling packed-bed reactors by employing sequencing batch operation

The biodegradation of phenol and 2,4,6-trichlorophenol (2,4,6-TCP) by immobilized white-rot fungal cultures was studied in pinewood chip and foam glass bead-packed trickling reactors. The reactors were operated in sequencing batch format. Removal efficiency increased over time and elevated influent phenol and 2,4,6-TCP (800 and 85 mg l(-1)) concentrations were removed by greater than 98% in 24-30 h batch cycles. Comparable performance between the packing materials was shown. Increased lignin peroxidase (LiP) activity was detected with the introduction of the compounds and optimum activity corresponded to optimum removal periods. Higher LiP activity (16.7-19 Ul(-1)) was detected in glass bead-packed reactor compared to wood chip reactor (0.2-5 Ul(-1)). The presence of Mn(2+) in the wood material possibly effected elevated manganese peroxidase (MnP) activity (0.3-5.8 Ul(-1)) compared to low to negligible activity in the glass bead reactor. Reactor performances are discussed in relation to sequencing batch operation and nutrient requirements necessary to induce and sustain fungal enzyme activity in inert vs. organic material packed systems.     

Enhanced aerobic granulation and nitrogen removal by the addition of zeolite powder in a sequencing batch reactor

The aim of this study was to evaluate the impact of zeolite powders on feasibility of rapid aerobic granulation in the column-type sequencing batch reactors. After 90 days' operation, aerobic granular sludge was formed in both reactors by altering influent chemical oxygen demand/nitrogen (COD/N) ratios. R1 with zeolite powders had better removal capabilities of COD and total nitrogen than R2, which was without zeolite powders. Mixed liquor volatile suspended solid concentrations of the two reactors were 7.36 and 5.45 g/L, while sludge volume index (SVI₃₀) values were 34.9 and 47.9 mg/L, respectively. The mean diameters of aerobic granular sludge in the above two reactors were 2.5 and 1.5 mm, respectively. Both reactors achieved the largest simultaneous nitrification and denitrification (SND) efficiency at an influent COD/N ratio of 8; however, R1 exhibited more excellent SND efficiency than R2. The obtained results could provide a novel technique for rapid aerobic granulation and N removal simultaneously, especially when treating nitrogen-rich industrial wastewater.     

Organics and nitrogen removal and sludge stability in aerobic granular sludge membrane bioreactor

Novel aerobic granular sludge membrane bioreactor (GMBR) was established by combining aerobic granular sludge technology with membrane bioreactor (MBR). GMBR showed good organics removal and simultaneous nitrification and denitrification (SND) performances for synthesized wastewater. When influent total organic carbon (TOC) was 56.8-132.6 mg/L, the TOC removal of GMBR was 84.7-91.9%. When influent ammonia nitrogen was 28.1-38.4 mg/L, the ammonia nitrogen removal was 85.4-99.7%, and the total nitrogen removal was 41.7-78.4%. Moreover, batch experiments of sludge with different particle size demonstrated that: (1) flocculent sludge under aerobic condition almost have no denitrification capacity, (2) SND capacity was caused by the granular sludge, and (3) the denitrification rate and total nitrogen removal efficiency were enhanced with the increased particle size. In addition, study on the sludge morphology stability in GMBR showed that, although some granular sludge larger than 0.9 mm disaggregated at the beginning of operation, the granular sludge was able to maintain the stability of its granular morphology, and at the end of operation, the amount of granular sludge (larger than 0.18 mm) stabilized in GMBR was more than 56-62% of the total sludge concentration. The partial disaggregation of large granules is closely associated with the change of operating mode from sequencing batch reactor (SBR) system to MBR system.     

Growth and survival of bacteria implicated in sudden infant death syndrome on cot mattress materials

AIMS: To compare growth and survival of selected bacteria implicated in sudden infant death syndrome (SIDS) on cot mattress polyurethane (PU) inner-foams and on different types of cot mattress cover materials. METHODS AND RESULTS: Escherichia coli, Staphylococcus aureus or Streptococcus pyogenes were inoculated onto swatches of new-unused cot mattress PU inner-foam and onto three types of cot mattress covers (polyvinyl chloride, cotton and polyester). The influence of inoculation cell density, relative humidity (RH) and temperature of incubation on survival was assessed by recovery of cells in 0.85% NaCl, with viable cell enumeration by plate counting on selective and differential media. Utilization of carbon and nitrogen sources within cot mattress PU was assessed by following growth on aqueous leachate from PU, and by colorimetric determination of aromatic amines. Good survival capability (>206 d) was shown by all three test species on PU inner-foam and on polyester mattress cover at high RH (75%), but only by Staph. aureus on PU at low RH (25%). Aqueous soluble material from PU foam supports bacterial growth; removal of aromatic amines from aqueous leachate from PU accompanies growth of Staph. aureus. CONCLUSIONS: Staphylococcus aureus has good survival capability on cot mattress PU foam, even at low RH. Soluble material within PU can serve as carbon and nitrogen sources for bacterial growth. SIGNIFICANCE AND IMPACT OF THE STUDY: Prolonged survival of Staph. aureus on PU at low RH could explain, in the context of the common bacterial toxins hypothesis, an increased risk of SIDS associated with used infant mattresses.     

Effect of influent nutrient ratios and hydraulic retention time (HRT) on simultaneous phosphorus and nitrogen removal in a two-sludge sequencing batch reactor process

A laboratory-scale anaerobic–anoxic/nitrification sequencing batch reactor (A₂N-SBR) fed with domestic wastewater was operated to examine the effect of varying ratios of influent COD/P, COD/TN and TN/P on the nutrient removal. With the increased COD/P, the phosphorus removals exhibited an upward trend. The influent TN/P ratios had a positive linear correlation with the phosphorus removal efficiencies, mainly because nitrates act as electron acceptors for the phosphorus uptake in the A₂N-SBR. Moreover, it was found that lower COD/TN ratio, e.g. 3.5, did not significantly weaken the phosphorus removal, though the nitrogen removal first decreased greatly. The optimal phosphorus and nitrogen removals of 94% and 91%, respectively were achieved with influent COD/P and COD/TN ratios of 19.9 and 9.9, respectively. Additionally, a real-time control strategy for A₂N-SBR can be undertaken based on some characteristic points of pH, redox potential (ORP) and dissolved oxygen (DO) profiles in order to obtain the optimum hydraulic retention time (HRT) and improve the operating reliability.     

An effective way to select slow-growing nitrifying bacteria by providing a dynamic environment

In this study, two laboratory scale sequencing batch reactors (SBRs) were conducted to study the stability of aerobic granules. The strategy was involved in stepwise increase in ammonium (NH4⁺-N) concentration in the influent. Results showed that the activity of nitrifying bacteria and diameter of the aerobic granules significantly increased with gradually increasing NH4⁺-N, which reached persistently new balances by homeostasis. As a result, the stability of aerobic granules was remarkably enhanced. The value of sludge volume index (SVI) was below 25 ml/g, the mean settling velocity was excellent up to 107 m/h. The NH4⁺-N removal efficiency averaged above 99% and total nitrogen (TN) removal was greatly enhanced and could reach 68%. Besides dissolved oxygen, the granules size was also a dominant factor to influence denitrification, which could gradually increase in variable conditions through homeostasis. Stable, dense and well-settling nitrifying granules can be developed for simultaneous nitrification and denitrification removal.     

Effects of temperature on simultaneous nitrification and denitrification via nitrite in a sequencing batch biofilm reactor

A laboratory scale experiment was described in this paper to enhance biological nitrogen removal by simultaneous nitrification and denitrification (SND) via nitrite with a sequencing batch biofilm reactor (SBBR). Under conditions of total nitrogen (TN) about 30 mg/L and pH ranged 7.15–7.62, synthetic wastewater was cyclically operated within the reactor for 110 days. Optimal operation conditions were established to obtain consistently high TN removal rate and nitrite accumulation ratio, which included an optimal temperature of 31 °C and an aeration time of 5 h under the air flow of 50 L/h. Stable nitrite accumulation could be realized under different temperatures and the nitrite accumulation ratio increased with an increase of temperature from 15 to 35 °C. The highest TN removal rate (91.9%) was at 31 °C with DO ranged 3–4 mg/L. Process control could be achieved by observing changes in DO and pH to judge the end-point of oxidation of ammonia and SND.     

Control of COD/N ratio for nutrient removal in a modified membrane bioreactor (MBR) treating high strength wastewater

A modified membrane bioreactor (MBR) system has been developed to evaluate the efficiency of nutrient removal in treating synthetic high strength water. This study examined the effect of influent COD/N ratio on this system. Results showed that above 95.0% removal efficiencies of organic matter were achieved; indicating COD removal was irrespective of COD/N ratio. The average removal efficiencies of total nitrogen (TN) and phosphate (PO(4)(3-)-P) with a COD/N ratio of 9.3 were the highest at 90.6% and 90.5%, respectively. Furthermore, TN removal was primarily based on simultaneous nitrification and denitrification (SND) process occurred in the aerobic zone. Decreased COD/N ratios to 7.0 and 5.3, TN removal efficiencies in steady-states were 69.3% and 71.2%, respectively. Both aerobic SND and conventional biological nitrification/denitrification contributed to nitrogen removal and the latter played dominant effect. PO(4)(3-)-P-release and uptake process ceased in steady-states of COD/N 7.0 and 5.3, which decreased its removal efficiency significantly.     

Nitrogen removal from aquaculture pond water by heterotrophic nitrogen assimilation in lab-scale sequencing batch reactors

The potential use of sequencing batch reactors (SBRs) as an alternative bio-flocs technology (BFT) approach in aquaculture was explored. One SBR was dosed with glycerol and one with acetate for the decrease of the nitrogen concentration in simulated aquaculture water by microbial assimilation. At an optimal C/N ratio between 10 and 15, the nitrogen removal efficiency reached up to 98% (=110 mg N L(-1) reactor day(-1)) for both SBRs. The estimated biomass productivity reached 0.62-0.94 g C L(-1)r eactor day(-1) for the glycerol SBR and 0.54-0.82 g C L(-1) reactor day(-1) for the acetate SBR. The floc protein content, indicating biomass quality, reached up to 57% if grown on glycerol. With acetate, it attained a value of 61%. The highest average poly-beta-hydroxybutyrate (PHB) content was 16% on a dry weight basis for the acetate biomass.     

Simultaneous nitrification, denitrification, and phosphorus removal from nutrient-rich industrial wastewater using granular sludge

The biological removal of nitrogen and phosphorus from nutrient-rich abattoir wastewater using granular sludge has been investigated. A lab-scale sequencing batch reactor, seeded with granular sludge developed using synthetic wastewater, was operated for 13 months under alternating anaerobic and aerobic conditions. It is demonstrated that the granules could be sustained and indeed further developed with the use of abattoir wastewater. The organic, nitrogen, and phosphorus loading rates applied were 2.7 gCOD L(-1) day(-1), 0.43 gN L(-1) day(-1), and 0.06 gP L(-1) day(-1), respectively. The removal efficiency of soluble COD, soluble nitrogen and soluble phosphorus were 85%, 93%, and 89%, respectively. However, the high suspended solids in the effluent limited the overall removal efficiency to 68%, 86%, and 74% for total COD, TN, and TP, respectively. This good nutrient removal was achieved through the process known as simultaneous nitrification, denitrification, and phosphorus removal, likely facilitated by the presence of large anoxic zones in the center of the granules. The removal of nitrogen was likely via nitrite optimizing the use of the limited COD available in the wastewater. Accumulibacter spp. were found to be responsible for most of the denitrification, further reducing the COD requirement for nitrogen and phosphorus removal. Mineral precipitation was evaluated and was not found to significantly contribute to the overall nutrient removal. It is also shown that the minimum HRT in a granular sludge system is not governed by the sludge settleability, as is the case with floccular sludge systems, but likely by the limitations associated with the transfer of substrates in granules.     

The effect of propionic to acetic acid ratio on anaerobic-aerobic (low dissolved oxygen) biological phosphorus and nitrogen removal

In this paper, three lab-scale sequencing batch reactors (SBR-A, B, and C) operated with anaerobic/aerobic (low dissolved oxygen, 0.15-0.45 mg L(-1)) configuration were long-term cultured, respectively with single acetic acid and propionic/acetic acid of 1/1 and 2/1 (carbon molar ratio), and the comparisons of anaerobic and aerobic transformations of phosphorus and nitrogen among them were made. With the increase of propionic/acetic acid, lower anaerobic phosphorus release and higher phosphorus release to short-chain fatty acids uptake ratio were observed, and less anaerobic and aerobic transformations of glycogen and poly-3-hydroxybutyrate as well as total polyhydroxyalkanoates occurred, but the transformations of poly-3-hydroxyvalerate and poly-3-hydroxy-2-methyvalerate increased. The phosphorus removal efficiency was respectively 81, 94 and 97% in SBR-A, B and C. Almost all ammonium was removed and no significant nitrite was accumulated at different propionic/acetic acid ratios. However, the nitrate accumulation and total nitrogen removal were observed to be affected by propionic/acetic acid ratio. The total nitrogen removal efficiency was 61, 68 and 82%, and the aerobic end nitrate concentration was 8.05, 6.40 and 3.54 mg L(-1) in three SBRs, respectively. All the above studies indicated that the sole acetic acid caused more nitrate accumulation than propionic and acetic acids mixture, and a pertinent increase of wastewater propionic/acetic acid ratio was of benefit to both nitrogen and phosphorus removal in an anaerobic/aerobic (low dissolved oxygen) biological wastewater treatment process.     

Effect of impeller type and stirring frequency on the behavior of an AnSBBR in the treatment of low-strength wastewater

The influence of impeller type and stirring frequency on the performance of a mechanically stirred anaerobic sequencing batch reactor containing immobilized biomass on an inert support (AnSBBR - Anaerobic Sequencing Batch Biofilm Reactor) was evaluated. The biomass was immobilized on polyurethane foam cubes placed in a stainless-steel basket inside a glass cylinder. Each 8-h batch run consisted of three stages: feed (10 min), reaction (460 min) and discharge (10 min) at 30 °C. Experiments were performed with four impeller types, i.e., helical, flat-blade, inclined-blade and curved-blade turbines, at stirring frequencies ranging from 100 to 1100 rpm. Synthetic wastewater was used in all experiments with an organic-matter concentration of 530 ± 37 mg/L measured as chemical oxygen demand (COD). The reactor achieved an organic-matter removal efficiency of around 87% under all investigated conditions. Analysis of the four impeller types and the investigated stirring frequencies showed that mass transfer in the liquid phase was affected not only by the applied stirring frequency but also by the agitation mode imposed by each impeller type. The best reactor performance at all stirring frequencies was obtained when agitation was provided by the flat-blade turbine impeller.     

Kinetic studies on urea hydrolysis by immobilized urease in a batch squeezer and flow reactor

The immobilization of urease on the reticulated polyurethane foam, and the kinetic phenomenon of urea hydrolysis by the resulting immobilized urease in both batch squeezer and circulated flow reactors were studied. Urease was immobilized with bovine serum albumin and glutaraldehyde on polyurethane foam support of 7 to 15 mum thickness. The residual apparent activity of urease after immobilization was about 50%. The good hydrodynamic property and flexibility of polyurethane foam were retained in solution after immobilization. A modified biofilm reactor model was used to describe the kinetic phenomenon of urea hydrolysis in both batch squeezer and circulated flow reactors. The characteristic parameters of the reactor model for both bioreactors were obtained by combining the Rosenbrock optimization method, the Rungs-Kutta method, and the Newton-Raphson method. The best-fit results were in good agreement with the experimental data. This study suggests another application of polyurethane foam in enzyme immobilization and immobilized enzyme reactors, which offers potential for practical applications in various bioreactors. (c) 1992 John Wiley & Sons, Inc.     

Characterization of the polyurethanolytic activity of two Alicycliphilus sp. strains able to degrade polyurethane and N-methylpyrrolidone

Two bacterial strains (BQ1 and BQ8) were isolated from decomposed soft foam. These were selected for their capacity to grow in a minimal medium (MM) supplemented with a commercial surface-coating polyurethane (PU) (Hydroform) as the carbon source (MM-PUh). Both bacterial strains were identified as Alicycliphilus sp. by comparative 16S rRNA gene sequence analysis. Growth in MM-PUh showed hyperbolic behavior, with BQ1 producing higher maximum growth (17.8 +/- 0.6 mg.ml(-1)) than BQ8 (14.0 +/- 0.6 mg.ml(-1)) after 100 h of culture. Nuclear magnetic resonance, Fourier transform infrared (IR) spectroscopy, and gas chromatography-mass spectrometry analyses of Hydroform showed that it was a polyester PU type which also contained N-methylpyrrolidone (NMP) as an additive. Alicycliphilus sp. utilizes NMP during the first stage of growth and was able to use it as the sole carbon and nitrogen source, with calculated K(s) values of about 8 mg.ml(-1). Enzymatic activities related to PU degradation (esterase, protease, and urease activities) were tested by using differential media and activity assays in cell-free supernatants of bacterial cultures in MM-PUh. Induction of esterase activity in inoculated MM-PUh, but not that of protease or urease activities, was observed at 12 h of culture. Esterase activity reached its maximum at 18 h and was maintained at 50% of its maximal activity until the end of the analysis (120 h). The capacity of Alicycliphilus sp. to degrade PU was demonstrated by changes in the PU IR spectrum and by the numerous holes produced in solid PU observed by scanning electron microscopy after bacterial culture. Changes in the PU IR spectra indicate that an esterase activity is involved in PU degradation.