Sequencing Batch Airlift Reactor Research Articles

Effects of micro-bubble aeration on the pollutant removal and energy-efficient process in a floc–granule sludge coexistence system

Abstract To investigate energy-saving approaches in wastewater treatment plants and decrease aeration energy consumption, this study successfully established a floc–granule coexistence system in a sequencing batch airlift reactor (SBAR) employing micro-bubble aeration. The analysis focused on granule formation and pollutant removal under various aeration intensities, and compared its performance with a traditional floc-based coarse-bubble aeration system. The results showed that granulation efficiency was positively associated with aeration intensity, which enhanced the secretion of extracellular polymeric substances (EPSs) and facilitated granule formation. The SBAR with the micro-aeration intensity of 30 mL·min−1 showed the best granulation performance (granulation efficiency 52.6%). In contrast to the floc-based system, the floc–granule coexistence system showed better treatment performance, and the best removal efficiencies of NH4+-N, TN, and TP were 100.0, 77.0, and 89.5%, respectively. The floc–granule coexistence system also enriched higher abundance of nutrients removal microbial species, such as Nitrosomonas (0.05–0.14%), Nitrospira (0.14–2.32%), Azoarcus (2.95–12.17%), Thauera (0.43–1.95%), and Paracoccus (0.76–2.89%). The energy-saving potential was evaluated, which indicated it is feasible for the micro-aeration floc–granule coexistence system to decrease the aeration consumption by 14.4% as well as improve the effluent.

Enhanced aerobic granular sludge formation by applying Phanerochaete chrysosporium pellets as induced nucleus.

The long start-up period is a major challenging issue for the widespread application of aerobic granular sludge (AGS). In this study, a novel rapid start-up strategy was developed by inoculating Phanerochaete chrysosporium (P. chrysosporium) pellets as the induced nucleus in a sequencing batch airlift reactor (SBAR) to enhance activated sludge granulation. The results demonstrated that P. chrysosporium pellets could effectively shorten the aerobic granulation time from 32 to 20days. The AGS promoted by P. chrysosporium pellets had a larger average diameter (2.60-2.74mm) than that without P. chrysosporium pellets (1.78-1.88mm) and had better biomass retention capacity and sedimentation properties; its mixed liquor suspended solids (MLSS) and sludge volume index (SVI30) reached approximately 5.2g/L and 45mL/g, respectively. The addition of P. chrysosporium pellets promoted the secretion of extracellular polymeric substances (EPS), especially protein (PN). The removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) in P. chrysosporium pellets reactor were 98.91%, 89.17%, 64.73%, and 94.42%, respectively, which were higher than those in the reactor without P. chrysosporium pellets (88.73%, 82.09%, 55.75%, and 88.92%). High throughput sequencing analysis indicated that several functional genera that were responsible for the formation of aerobic granules and the removal of pollutants, such as Acinetobacter, Pseudomonas, Janthinobacterium, and Enterobacter, were found to be predominant in the mature sludge granules promoted by P. chrysosporium pellets.

Dissolved oxygen concentration as a strategy to select type and composition of bacterial storage lipids produced during oilfield produced water treatment

Oilfield produced water (PW) management and treatment represents a significant cost to oil producers. Alcanivorax borkumensis is a marine bacteria capable of converting hydrocarbons into storage lipids, currently of great interest as raw materials for biofuel or oleochemical industries. In this study, the effect of dissolved oxygen (DO) concentration on the production of storage compounds by A. borkumensis SK2 was investigated in a sequencing batch airlift reactor treating saline oilfield produced water (PW). Intracellular lipids accumulation decreased from 0.74 g/g cellular dry weight (CDW) (7–8 mg/L O2) to 0.51 g/g CDW under 2–3 mg/L O2 and 0.45 g/g CDW during alternated DO concentrations of 7–8/1–2 mg/L O2 (famine/feast stage). Triacylglycerols were the main lipids accumulated for DO of 7–8 and 2–3 mg/L O2. During alternated DO conditions, accumulation of polyhydroxyalkanoates (0.41 g/g CDW) was observed. Extracellular lipids production were mainly wax esters and not significantly affected by DO concentration. Fatty acid (FA) composition and relative proportions of saturated and unsaturated FA in the produced compounds was also affected by oxygen availability. The obtained results show that selection of DO concentration during PW treatment can be used as a strategy to direct bacterial metabolism to production of a particular compound of interest. Hydrocarbon removal efficiencies in the range of 90%–96% were achieved showing that is possible to reduce aeration costs without compromising PW treatment and concomitant production of valuable compounds.

Development of aerobic granulation system for simultaneous removal of C, N, and P in sequencing batch airlift reactor

Conventional biological nutrient removal techniques often have disadvantages like low removal efficiencies, requirement of large footprint, and excess sludge production. Ever increasing stringent discharge standards demand for alternative technologies. In this context aerobic granular sludge (AGS) has evolved as a promising technology for complete nutrient removal. However, degradation of structural integrity of aerobic granules in long run is a prime concern of this technology. This work attempts to develop stable aerobic granules in an automated sequential batch airlift reactor (SBAR) for simultaneous C, N, and P removals under alternating aerobic and anoxic conditions. The reactor was operated at high sludge retention time (SRT). Combined operating strategies of varying dissolved oxygen (DO) concentration and feed cycle times were followed to optimize the conditions for effective granulation and subsequent removal efficiencies. Profiles of extracellular polymeric substances (EPS) and sludge volume index (SVI) were monitored. Optimum removal efficiencies of NH4+-N (92.7%), TN (90.6%), COD (90.1%), and PO43--P (83.2%), and granules of size 1.3–8 mm were achieved in phase IV at operational DO of 1–2 mg/L, and feeding intervals of 15 h and 9 h. NH4+-N (R2 = 0.97, k = 0.5093/h) and PO43--P (R2 = 0.95, k = 0.2574/h) removals were fitted well with first order kinetic model and that of COD (R2 = 0.97, k = 0.0032 L/mg/h) followed second order kinetics. This process is economical as effective biological nutrient and organics removal occurs in a single reactor without requirement of alkalinity supply, and negligible excess sludge production. The process requires small foot print and applicable for decentralized wastewater management in University campuses/tourist resorts/apartment complexes.

Sequencing batch airlift reactors (SBAR): a suitable technology for treatment and valorization of mineral oil wastewaters towards lipids production

Produced water (PW) and spent oil-based wastewaters are some of the largest mineral oil wastewaters produced. Due to the high toxicity of hydrocarbons, several countries set stringent discharge limits and its treatment is compulsory before discharge. In this work, biological treatment of mineral oil wastewaters coupled with the production of bacterial lipids is demonstrated in sequential batch airlift reactors (SBAR). Two SBAR (2 L working volume) were used for treatment of PW and lubricant-based wastewater (LW), inoculated with Alcanivorax borkumensis SK2 (SBARAb+PW) and Rhodococcus opacus B4 (SBARR.o+LW), respectively. A total petroleum hydrocarbon removal (TPH) efficiency up to 96% and 80% were achieved for SBARAb+PW and SBARR.o+LW, respectively. Intracellular lipids production in SBARAb+PW increased when lower TPH/N ratios and higher feast stage duration were applied (up to 0.74 g g-1 cell dry weight (CDW)), whereas in SBARR.o+LW higher lipids production was observed for higher TPH/N ratios (0.94 g g-1 in CDW). Triacylglycerols (TAG) were the main intracellular lipid accumulated in both SBARAb+PW and SBARR.o+LW operations, while wax ester (WE) production was only observed extracellularly in the SBARAb+PW.

Development and application of Sequencing Batch Airlift Reactor for Domestic Sewage Treatment

Aiming at the demand of decentralized domestic sewage treatment in rural areas, Sequencing Batch Airlift Reactor (SBAR) for domestic sewage treatment was developed and applied for sewage disposal of an office building in shenjiadun village, Deqing, Zhejiang Province. The device doesn’t need to set up sedimentation tank and sludge reflux system. It has a good precipitation effect and only occupies a small area. In the aspect of control, it adopts the self-researched embedded software system. And it integrates GPRS/GSM/SMS/CDMA/Internet communication technology and high-precision electrical parameter measurement technology. The actual operation results show that the device can ensure sufficient contact between sludge and waste water. It can effectively remove BOD5, CODCr, ammonia nitrogen and total nitrogen from domestic sewage. And it has the advantages of low investment, low energy consumption, high automation and simple operation. Therefore, this device has important popularization value in the field of distributed treatment of rural domestic sewage.

Startup of granulation of sludge in sequencing batch airlift reactor for simultaneous removal of nitrogen and organic carbon from tannery wastewater

The transition from flocculent to granular sludge process was investigated in Sequencing Batch Airlift Reactor (SBAR) for the treatment of synthetic tannery wastewater. Chemical Oxygen Demand (COD) loading rate of 6.3 kg/m3.d and nitrogen loading rate of 0.425 kg/m3.d were applied to the reactor for 105 days using simulated tannery wastewater. The flocculent sludge was transformed to granular sludge when the operating settling time was reduced sequentially. Based on the current findings of the study, the aerobic granules formed had a MLSS concentration of 12.3 g/L, biomass density of 6.1 g /L granule, settling velocity of 30−40 m/h, SVI of 16−20 ml/g TS and size distribution in the range 1.8–3.2 mm. Evaluation of the performance of the reactor showed a very good quality effluent with average COD, NH4-N and TN removal of 97.7 ± 1.5 (%), 87.1 ± 11.8 and 74.43 ± 11.7 (%) respectively. The effect of granulation on the existence and relative abundance of selected bacteria gene involved in nitrogen cycle was analyzed by PCR and qPCR. The result confirmed the existence of AOB-amoA, nirK and PLA46+Amx820 gene. The results for qPCR also confirmed that the relative abundance of AOB-amoA and PLA46+Amx820 was higher in the reactor compared to the control.

Influence of N/COD ratios and nitrogen forms on aerobic granulation in sequencing batch airlift reactor

Influence of N/COD ratios and nitrogen forms on aerobic granulation in sequencing batch airlift reactor

Sequencing batch airlift reactor system for simultaneous removal of nitrogen and organic carbon from synthetic tannery wastewater

Sequencing batch airlift reactor system for simultaneous removal of nitrogen and organic carbon from synthetic tannery wastewater

Rapid formation of aniline-degrading aerobic granular sludge and investigation of its microbial community succession

Aniline is one of common by-products in several industries such as petroleum and chemical and its discharge attracts increasing concern in recent years. Aerobic granular sludge (AGS) technology is regarded as one of the most promising biological processes. However, there are some drawbacks such as long start-up especially when the system is fed with toxic pollutants (e.g., aromatic compounds). In this study, rapid formation of AGS for aniline biodegradation was investigated. The aerobic granules were successfully developed in a sequencing batch airlift reactor (SBAR) fed with aniline-containing wastewater within 15 days. The sludge volume index decreased from 58.47 to 30.31 mL g−1 after AGS was formed. It was also found that extracellular polymeric substances (EPS) especially protein was increased significantly during aerobic granulation. Besides, the average removal efficiencies of aniline and COD from day 3–15 (the period since early observation of pinpoint particles in the mixed liquor) were 99.93% and 90.59%, respectively. NH4+-N was also remarkably reduced in the SBAR. Through pyrosequencing analysis, Proteobacteria was the most abundant phylum during granulation. There were several genera responsible for aniline biodegradation and EPS secretion such as Pseudomonas was found to be predominant in the system. The rapid formation of AGS and high removal efficiency of aniline and COD in the present system might provide an alternative for treating industrial effluents with presence of aniline.

Effects of the Food-to-Microorganism (F/M) Ratio on N2O Emissions in Aerobic Granular Sludge Sequencing Batch Airlift Reactors

The present study investigated the effect of the food-to-microorganism (F/M) ratio on nitrous oxide (N2O) emissions in aerobic granular sludge sequencing batch airlift reactors. Three identical sequencing batch airlift reactors were fed with sodium acetate-based wastewater at different chemical oxygen demand (COD) concentrations, resulting in F/M ratios from 0.2 to 0.67 g COD/g SS. The results indicated that N2O emissions increased with an increase of the F/M ratio. N2O emissions at the high F/M ratio of 0.67 g COD/g SS were the highest (4.4 ± 0.94 mg/d). The main source of the high N2O emissions at the F/M ratio of 0.67 g COD/g SS was nitrifier denitrification, rather than heterotrophic denitrification, confirmed by the qPCR (quantitative real-time PCR) results. The heterotrophic denitrification was destroyed by the DO (dissolved oxygen) diffusing into the sludge particles with porous structures. This study offers theoretical support to study the N2O emissions in aerobic granular sludge, and can provide guidance for conducting risk assessment and enhancing our ability to predict N2O production in aerobic granular sludge at different F/M ratios.

Seawater-based wastewater accelerates development of aerobic granular sludge: A laboratory proof-of-concept

This study aimed to develop an aerobic granular sludge process for the efficient treatment of highly saline wastewater and understand the granulation process in a seawater-based multi-ion matrix. Five identical sequencing batch airlift reactors (SBARs) are used to treat synthetic saline sewage with different proportions of real seawater (0%–100%). The results confirm that aerobic granular sludge can be successfully developed with various proportions of seawater up to 100% and show that seawater not only significantly accelerates granulation but also generates stronger granular structures than does freshwater. The increased presence of gel-forming alginate-like exopolysaccharides in the granules explains why a greater proportion of seawater leads to higher density and improves the cohesive strength of the granules. SEM-EDX analysis further revealed substantial presence of both Ca2+ and Mg2+ phosphate in the granule core as well as in the outer layers providing extra bridging forces in addition to alginate-like exopolysaccharides for accelerating the granule formation and maintaining the structure. It is hoped that this work could explore another approach for saline sewage treatment and bring some clues for the mystery of granulation mechanism.

Modified Sequencing Batch Airlift Reactor Capability in MTBE Removal

The aim of this study was to investigate MTBE removal efficiency using sequencing batch airlift reactor (SBAR) and to determine the share of aeration and adsorption processes during the operation. The present study was conducted with a new design of the system (cubic area and embedded baffle). The reactor was applied in 4-h cycles, which included 2 min filling, 210 min aeration, 5 min sedimentation, 8 min draw, and 15 min idle time. One week after start-up, the initial brown granules were observed. During the operation, some granules were formed with the size of 2–6 mm, average settling velocity and density of 0.66 cm/s and 0.06 g/mL, respectively. The results showed that COD removal efficiency was over 94 percent.

Recovery of phosphorus via harvesting phosphorus-accumulating granular sludge in sequencing batch airlift reactor

A novel approach was developed for phosphorus recovery from wastewater through thermal treatment of matured phosphorus-accumulating granular sludge cultivated in sequencing batch airlift reactor (SBAR) system. Results showed that SBAR system had stable performances, in which COD, total phosphorus (TP) and total nitrogen (TN) removal efficiencies were stabilized at 80%, 89% and 86%, respectively. The matured granules were gathered from SBAR reactor and heated at relatively low temperature (100°C, 200°C, 300°C). The total P content in thermal treated granular sludge was more than half of total nutrient. Furthermore, the phosphorus release rate for treated granules was negatively correlated with thermal treatment temperature. These results demonstrated that the granules harvested from SBAR system followed with thermal pre-treatment could probably be applied as excellent slow-release phosphorus fertilizer. Hence, low temperature treatment of phosphate-accumulating granules is efficient for phosphorus recovery from wastewater, which is likely to promote the application of granulation technology.

Rapid formation and pollutant removal ability of aerobic granules in a sequencing batch airlift reactor at low temperature

ABSTRACTThe start-up of an aerobic granular sludge (AGS) reactor at low temperature was more difficult than at ambient temperature.The rapid formation and characteristics of AGS in a sequencing batch airlift reactor at low temperature were investigated. The nutrient removal ability of the system was also evaluated. It was found that compact granules with clear boundary were formed within 10 days and steady state was achieved within 25 days. The settling properties of sludge were improved with the increasing secretion of extracellular polymeric substances and removal performances of pollutants were enhanced along with granulation. The average removal efficiencies of COD, NH4+–N, total nitrogen (TN), total phosphorus (TP) after aerobic granules maturing were over 90.9%, 94.7%, 75.4%, 80.2%, respectively. The rise of temperature had little impact on pollutant biodegradation while the variation of dissolved oxygen caused obvious changes in TN and TP removal rates. COD concentrations of effluents were below 30 mg l−1 in most cycles of operation with a wide range of organic loading rates (0.6–3.0 kg COD m−3 d−1). The rapid granulation and good performance of pollutant reduction by the system might provide an alternate for wastewater treatment in cold regions.

The Formation and Stabilization of Aerobic Granular Sludge in a Sequencing Batch Airlift Reactor for Treating Tapioca-Processing Wastewater

The Formation and Stabilization of Aerobic Granular Sludge in a Sequencing Batch Airlift Reactor for Treating Tapioca-Processing Wastewater

Cultivation of granular sludge with hypersaline oily wastewater

The time required to stabilise mature aerobic granules is rather variable. In addition, cultivation time and the structural characteristics of granules seem to be related to the nature of wastewater influent. Granular sludge has been used for the treatment of several industrial wastewaters, but nothing has been reported about wastewater characterized by the simultaneous presence of hydrocarbons and high chloride concentration. In this work, the authors analysed the granulation process and performance as well as the physical characteristics of aerobic granules in two Granular Sequencing Batch Airlift Reactors (GSBARs), fed with acetate-based synthetic wastewater in reactor 1 (R1) and with a mixture of real and simulated slop (R2). The results obtained in 100 days show that full granulation was achieved in both reactors. The granules in R2 developed more quickly, but they appeared slightly unstable and more susceptible to breaking. Despite high salt concentration, the efficiency of phosphorous and carbon removal was satisfactory. Low nitrification activity was observed in R1, confirming that a longer time is necessary to obtain the acclimation of autotrophic biomass in aerobic granules. In R2 the combined effect of salinity and hydrocarbons caused the inhibition of the autotrophic biomass, with the consequence that nitrification was absent. Hydrocarbons were initially removed by adsorption afterwards by biological degradation with a removal efficiency of over 90%.

Interaction between phosphorus removal and hybrid granular sludge formation under low hydraulic selection pressure at alternating anaerobic/aerobic conditions

The hybrid granular sludge (HGS) formation and its performances on phosphorus removal were investigated in a sequencing batch airlift reactor. Under conditions of low superficial air velocity (SAV = 0.68 cm s−1) and relatively long settling time (15–30 min), aerobic granules appeared and coexisted with bio-flocs after 120 days operation. At the stable phase, 54% of total suspended solid (m/m) was granular sludge with the two typical sizes (Dmean = 1.77 ± 0.33 and 0.89 ± 0.11 mm) in the reactor, where the settling velocity was 98.7 ± 12.4 and 37.8 ± 0.9 m h−1 for the big and small granules. With progressive extension of anaerobic time from 15 to 60 min before aerobic condition per cycle during the whole experiment, the HGS system can be maintained at a high total phosphorus removal efficiency (ca. 99%) since Day-270. The phosphorus content (wt %) in biomass was respectively 9.54 ± 0.29, 7.60 ± 0.48 and 6.15 ± 0.59 for the big granules, small granules and flocs.

Ammonia and phenol removal in an internal-circulate sequencing batch airlift reactor.

An internal-circulate sequencing batch airlift reactor (IC-SBAR) has been developed to evaluate the efficiency of phenol and ammonia removal in treating synthetic wastewater. This study examined the effect of operation cycle on this system. Results showed that above 97.0% removal efficiencies of ammonia and phenol were achieved, which indicated that ammonia and phenol removals were not related to operation cycle. The average removal efficiency of 91.7% for chemical oxygen demand (COD) was achieved when the static/aerobic/settling time was 240 min/440 min/40 min. It was found that COD removal efficiency increased due to the time of operation cycle being prolonged. The average removal efficiencies of total inorganic nitrogen (TIN) were 65.8, 69.3 and 68.9% when average TIN concentrations were 78.0, 97.6 and 88.4 mg/L, respectively, in the influent. A cycle study showed that most phenol was degraded by aerobic microbes. Increasing the static time from 120 to 240 min resulted in the accumulation of NO2(-)-N, which indicated that the structures of the nitrifying bacterial community were changed.

The Effect of Setting Time to the Formation of Aerobic Granular Sludge in SBAR under Low Organic Loading

The setting time was regarded as the selection pressure to make the particles which were unable to get acclimatized to that cultivation circumstance so as to get the aerobic granular sludge which own excellent setting ability with screening and beneficiation. The internal-circulate sequencing batch airlift reactor (SBAR) process was adopted in this experiment to investigate the effect of setting time to the formation of aerobic granular sludge in SBAR under low organic loading. The results showed that aerobic granular sludge with an average particle diameter of 4.0 mm had a good settling ability with spherical or ellipsoidal, smooth and dense on surface, furthermore, the removal rates of NH3-N,TP and CODCr were 96%, 94% and 90% ,respectively. The setting time can be treated as the dominant element for the control of formation and characteristics of aerobic granular sludge to a certain degree in its forming process.