Investigation on the formation and kinetics of glucose-fed aerobic granular sludge

Aerobic granular sludge was cultivated in a glass sequencing batch reactor (SBR) with glucose synthetic wastewater. The spherical shaped granules were observed on 4th day with the mean diameter of 0.1 mm. With the increase of chemical oxygen demand (COD) concentration of the influent, aerobic granules grew matured, the size of which ranged from 1.2 to 1.9 mm. The aerobic granular sludge could sustain high organic loading rate (about 4.0 g COD L⁻¹ d⁻¹), with good settling ability (settling velocity 36 m/h) and high biomass concentration (MLSS 6.7 ±0.2 g/L). Experimental data indicated that the substrate utilization and biomass growth kinetics followed Monod's kinetics model approximately. The corresponding kinetic coefficients of maximum specific substrate utilization rate (k), half velocity coefficient (K_s), growth yield coefficient (Y) and decay coefficient (K_d) were 13.2 d⁻¹, 275.8 mg/L, 0.183–0.250 mg MLSS/mg COD and 0.023–0.075 d⁻¹, respectively, which made aerobic granules have short setup period, high rate of substrate utilization and little surplus sludge.     

Liquid state fermentation of apple pomace sludge for the production of ligninolytic enzymes and liberation of polyphenolic compounds

Ligninolytic enzyme production and polyphenolic compound extraction by liquid-state culture of Phanerochaete chrysosporium ATCC 24275 was investigated by employing apple pomace sludge and synthetic medium. Different physico-chemical and biological parameters namely viscosity, zeta potential and particle size, viability and enzyme production were investigated. The ligninolytic enzyme production was higher in apple pomace sludge (45 U/l of laccase, 220 U/l of MnP and 6.5 U/l of LiP) than in synthetic medium (17 U/l of laccase, 37 U/l of MnP and 6 U/l). These maximal activities were found during the stationary and decline phase. It was also found that enzyme production was strongly correlated with P. chrysoporium viability in both synthetic medium and apple pomace sludge. Moreover, physico-chemical parameters, such as particle size, zeta potential and viscosity were strongly correlated to the viability of P. chrysosporium and to the ligninolytic enzyme production. An increase in polyphenol content extracted by acetone (383–720 mg GAE/l) was observed during fermentation of apple pomace and it was found that the polyphenol content extracted by ethanol increased ～1.5 fold until 67 h of fermentation and later it decreased. It was found that antioxidant activity increased to 35% and eventually decreased based on the change in the polyphenol content.     

Improvement of sludge anaerobic degradability by combined electro-flotation and electro-oxidation treatment

Recently, bioenergy recovery from sludge biomass has attracted increasing attention due to the high demand for renewable energy resources. In order to enhance methane production from sludge biomass, electrochemical treatment can be used as a novel and efficient pretreatment for the hydrolysis of sludge biomass. In this study, a combined electro-flotation and electro-oxidation pretreatment was employed to improve the anaerobic degradability of sludge biomass. Electro-flotation was efficient in separating flocs in the mixed liquor and led to a sludge volume reduction greater than 60% after 10 min of operation at a current density of 4.72 mA cm⁻². Electro-oxidation using IrO₂/Ti anode was performed to improve the anaerobic degradability of sludge and resulted in a 30% increase in COD solubilization after 30 min of operation at current density of 9.45 mA cm⁻². The factors affecting electro-oxidation, i.e. the gap width between anode and cathode, current density and applied voltage, were investigated to optimize the operating conditions. A biochemical methane potential assay demonstrated that the anaerobic biodegradability of sludge was enhanced by combined electro-flotation and electro-oxidation pretreatment.     

A half-submerged integrated two-phase anaerobic reactor for agricultural solid waste codigestion

Anaerobic digestion is widely used in bioenergy recovery from waste. In this study, a half-submerged, integrated, two-phase anaerobic reactor consisting of a top roller acting as an acidogenic unit and a recycling bottom reactor acting as a methanogenic unit was developed for the codigestion of wheat straw (WS) and fruit/vegetable waste (FVW). The reactor was operated for 21 batches (nearly 300 d). Anaerobic granular sludge was inoculated into the methanogenic unit. The residence time for the mixed waste was maintained as 10 d when the operation stabilized, and the temperature was kept at 35 °C. The highest organic loading rate was 1.37 kg VS/(m³ d), and the maximum daily biogas production was 328 L/d. Volatile solid removal efficiencies exceeded 85%. WS digestion could be confirmed, and efficiency was affected by both the ratio of WS to FVW and the loading rate. The dominant bacteria were Bacteroides-like species, which are involved in glycan and cellulose decomposition. Methanogenic community structures, pH levels, and volatile fatty acid concentrations in the acidogenic and methanogenic units differed, indicating successful phase separation. This novel reactor can improve the mass transfer and microbial cooperation between acidogenic and methanogenic units and can efficiently and steady codigest solid waste.     

Biotransformation of 2-phenylethanol to phenylacetaldehyde in a two-phase fed-batch system

Phenylacetaldehyde (PA) can be produced by the oxidation of 2-phenylethanol (PE) through biotransformation. In order to prevent substrate and product inhibitions and the transformation of the PA to phenylacetic acid (PAA), utilization of a two-phase system is very attractive. Gluconobacter oxydans B-72 was used as the microorganism and iso-octane as the solvent. The effect of initial substrate concentration on the PA production was investigated in single- and two-phase systems. In the single-phase system, substrate inhibition occurred above 5 g/l, and in the two-phase system, above 7.5 g/l. Substrate inhibition kinetics were also studied in the two-phase system and kinetic constants were determined as r_max=0.64 g/l min, K_M=8.15 g/l, K_PA=2.5 g/l. Because it was observed that two-phase system is insufficient to remove the substrate inhibition effect, fed-batch operation was utilised in this study. For 7.5 g/l of PE, 1.65, 3.85, and 7.35 g/l of PA were obtained in the single-phase, two-phase, and two-phase three fed-batch systems, respectively. Effect of biotransformation time, initial substrate concentration, agitation speed, and fed-batch number on the PA production was investigated in a two-phase fed-batch system by the response surface methodology (RSM). The optimum values were found as 3 fed-batch number, 2.75 g/l initial substrate concentration, 150 rpm agitation speed, and 65 min of one batch biotransformation time. In order to verify these results, an experiment was performed at these optimum conditions and 7.10 g/l of PA concentration was obtained.     

Anaerobic submerged membrane bioreactor (AnSMBR) treating low-strength wastewater under psychrophilic temperature conditions

An anaerobic submerged membrane bioreactor (AnSMBR) treating low-strength wastewater was operated for 90 days under psychrophilic temperature conditions (20 °C). Besides biogas sparging, additional shear was created by circulating sludge to control membrane fouling. The critical flux concept was used to evaluate the effectiveness of this configuration. Biogas sparging with a gas velocity (U_G) of 62 m/h together with sludge circulation (94 m/h) led to a critical flux of 7 L/(m² h). Nevertheless, a further increase in the U_G only minimally enhanced the critical flux. A low fouling rate was observed under critical flux conditions. The cake layer represented the main fouling resistance after 85 days of operation. Distinctly different volatile fatty acid (VFA) concentrations in the reactor and in the permeate were always observed. This fact suggests that a biologically active part of the cake layer contributes to degrade a part of the daily organic load. Hence, chemical oxygen demand (COD) removal efficiencies of up to 94% were observed. Nevertheless, the biogas balance indicates that even considering the dissolved methane, the methane yield were always lower than the theoretical value, which indicates that the organic compounds were not completely degraded but physically retained by the membrane in the reactor.     

Role and characteristics of problematic biofilms within the removal and mobility of trace metals in a pilot-scale membrane bioreactor

The characteristics of problematic biofilms (i.e., fouling and clogging layers) were studied with regards to the removal and fate of trace metals (contents well under 100 μg/L) during the long-term operation of a pilot-scale membrane bioreactor for the treatment of real wastewaters from a large industrial area.Results showed that clogging layer was more effective than suspended activated sludge in the biosorption of As > Zn > Ni > Cd > Sb > Fe > Se due to the synergic effects of extracellular polymeric compounds and metal-resistant bacteria. In fact the selective microbial speciation of the phylum of Bacteroidetes, which is highly resistant to heavy metals, was observed in the clogging sludge in spite of the very low concentration of dissolved metals in the bioreactor.Compared to the suspended activated sludge, the clogging layer enhanced the biosorption of very toxic substances such as As, Cd and Ni. In fact, the metal contents were respectively: 7.9–7.4 vs. 690–840 μgAs/kgTS; 1.5–2.2 vs. 149–219 μgCd/kgTS; 58.8–71.7 vs. 227–298 μgNi/kgTS. Then, the potential desorption of metals during the membrane acid cleanings was estimated as relevant as 10–15% of the metals associated to the clogging sludge. The combined effects of pH and the selected microbial community, and the minor effect of the redox potential, let us conclude on the major importance of bio-sorption/desorption mechanisms with respect to bio-precipitation/dissolution.     

Aerobic granulation in sequencing batch reactors with different reactor height/diameter ratios

Effects of reactor height/diameter ratios ranged from 24 to 4 corresponding to reactor settling velocities from 12 to 2 m h^?1 on aerobic granulation were investigated. It was found that granules appeared after 1-week operation and granule volume percentages exceeded 50% after 2–3 weeks in four reactors. In addition, similar granule fraction of 94–96% was found at steady state in all four reactors. Sludge volume index (SVI), average sludge size, biomass density and granule settling velocity at steady state were around 50 ml g^?1, 1800 μm, 53 g l^?1 and 40 m h^?1, respectively, in four reactors. Extracellular polymeric substances (EPS) and specific oxygen uptake rate (SOUR) were around 38 mg g^?1 VSS and 40 mg O₂ g^?1 VSS h^?1, respectively. Denaturing gradient gel electrophoresis (DGGE) fingerprint of sludge in four reactors showed the same microbial population shift during the start-up period and same microbial community structure during steady-state period. These results recommended strongly that reactor height/diameter ratio or reactor setting velocity in the used range in this study did not affect granule formation, physical characteristics, microbial community structure of granules and stable operation of granular sludge reactor. Reactor height/diameter ratio thus can be very flexible in the practice, which is important for the application of aerobic granule technology.     

Biosorption of Fe3+ from aqueous solution by a bacterial dead Streptomyces rimosus biomass

The iron biosorption capacity of a Streptomyces rimosus biomass treated with NaOH was studied in batch mode. After pretreatment of biomass at the ambient temperature, optimum conditions of biosorption were found to be: a biomass particle size between 50 and 160 μm, an average saturation contact time of 4 h, a biomass concentration of 3 g/l and a stirring speed of 250 rpm. The equilibrium data could be fitted by Langmuir isotherm equation. Under these optimal conditions, 122 mg _Fe/g_biomass were fixed.     

Acute impact of tetracycline and erythromycin on the storage mechanism of polyhydroxyalkanoates

The study investigated acute impact of tetracycline and erythromycin on substrate storage under aerobic conditions. A fill and draw reactor fed with peptone mixture was maintained at steady-state at a sludge age of 10 days; the acclimated biomass was used in a series of batch runs. The first run served as control reactor with organic substrate alone and the others were started with antibiotic doses of 50 mg/L and 200 mg/L for assessing intracellular storage. Parallel batch reactors were also conducted for recording oxygen uptake rate profiles. Both antibiotics enhanced substrate storage, leading to higher levels of polyhydroxyalkanoates incorporated into biomass, but they impaired its internal utilization for microbial growth. The observed decrease in oxygen consumption under the acute effect of antibiotics could partially be related to substrate storage – except for 50 mg/L of erythromycin dosing – suggesting an additional substrate binding mechanism by antibiotics, leading to residual biodegradable substrate.     

Adaptation of anaerobic biomass to saline conditions: Role of compatible solutes and extracellular polysaccharides

This study investigated the role of compatible solutes, extracellular polysaccharides (EPS), and nutrients on anaerobic biomass when stressed with salinity. When 1 mM of osmoregulants glycine betaine, α-glutamate and β-glutamate were added separately to serum bottles containing biomass not adapted to sodium, and fed with glucose and 35 g NaCl/L, all the compatible solutes were found to alleviate sodium inhibition, although glycine betaine was found to be the most effective. The effect of glycine betaine on different anaerobic bacterial groups under salinity stress was monitored using VFAs, and showed that methanogens were more protected than propionate utilisers. Moreover, the addition of 1 mM of glycine betaine to anaerobic biomass not adapted to salinity resulted in significantly higher methane production rates compared with anaerobic biomass that was exposed for 4 weeks to 35 g NaCl/L. Interestingly, under saline batch conditions when the medium was replaced totally the culture produced less methane than when only new substrate was added due to compatible solutes cycling between the media and the cell. The elimination of macronutrients from the medium was found to have a more pronounced negative effect on biomass under saline compared with nonsaline conditions, and because of the synthesis of N-compatible solutes sufficient nutrients should always be present. On the other hand, the absence from the medium of micronutrients did not further reduce biomass activity under salinity. Finally, a higher production of EPS was obtained from biomass exposed to higher salt concentrations, and its composition was found to change under different saline conditions and time. As a result, biomass under saline conditions had a slightly higher mean flock size compared with the biomass that was not subjected to salt.     

Effects of dose and adaptation time of a specific blend of essential oil compounds on rumen fermentation

Essential oils can be used as natural additives in animal feeds. The present study evaluated the effects of three different doses and different adaptation times of a specific blend of essential oils (BEO) on rumen microbial fermentation. Eight dual flow continuous culture fermenters (1320 ml) were used in two periods of 9 days each to study the effects of increasing doses of BEO. Treatments were: CTR (no BEO), D5 (5 mg/l of BEO), D50 (50 mg/l of BEO) and D500 (500 mg/l of BEO). During the last 3 days, samples were taken at 0, 2, 4 and 6 h after the morning feeding and analyzed for large peptide (LPep), small peptides plus amino acid (SPep + AA) and ammonia N concentrations, and at 2 h after feeding for volatile fatty acids (VFA) concentration and profile. The D5 increased total VFA concentration, acetate proportion and acetate to propionate ratio, and decreased propionate and valerate proportion, compared with CTR. The concentration of LPep N tended (P=0.08) to be lower for D5 compared with CTR. In the second experiment, eight sheep were used to study the effects of long-term adaptation of rumen fluid to BEO on ruminal fermentation. Four sheep were assigned at random to the CTR treatment (no BEO) and four sheep were adapted to BEO (110 mg/day of BEO) for 4 weeks (ADBEO). After 4 weeks samples of ruminal fluid were obtained at 0 and 3 h after the morning feeding and in 2 consecutive days using an oro-ruminal probe. Samples were analyzed for LPep, SPep + AA and ammonia N concentrations, total and individual VFA, and pH. Treatment ADBEO tended (P<0.10) to increase acetate proportion and decrease valerate proportion, compared with CTR. Ruminal fluid collected from each of CTR and ADBEO sheep was used to study in vitro fermentation profile of soybean meal, corn meal, alfalfa hay and ryegrass hay. Treatments were: Control fluid (CTR without BEO), CTR fluid plus a single dose of BEO (11 mg/l; CTR + BEO) and ADBEO fluid plus a single dose of BEO (11 mg/l; ADBEO + BEO). Acetate proportion and acetate to propionate ratio was higher, and propionate and isovalerate proportion, and BCVFA and ammonia N concentration were lower in ADBEO + BEO fluid compared with CTR fluid. The addition of essential oils can shift the microbial fermentation in the rumen by increasing the acetate to propionate ratio and inhibiting deamination.     

Adding Fe0 powder to enhance the anaerobic conversion of propionate to acetate

Propionate is an unfavorable substrate for the anaerobic digestion because it is thermodynamically difficult to be decomposed into acetate. An attempt to enhance the decomposition of propionate by adding Fe⁰ powder (10 g) into an acidogenic reactor (A1) with propionate as the sole carbon source was made in this study. The results showed that the propionate conversion rate (67–89%) in A1 were higher than that in a reference reactor (43–77%) without dosing of Fe⁰ (A2). The enhanced conversion of propionate caused both chemical oxygen demand removal (COD) (57–79%) and acetate production (178–328 mg/L) in A1 to increase significantly. Although Fe⁰ contributed the H₂ production chemically, the H₂ content of A1 was less than that of A2. The reason was ascribed to the enhanced utilization of H₂ for the homoacetogenesis. It was calculated that the Gibbs free energy in the decomposition of propionate was decreased by about 8.0–10.2% with the dosing of Fe⁰. Also, the activities of enzymes related to the acetogenesis were enhanced by 2–34-folds. Fluorescence in situ hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE) analysis indicated that Fe⁰ increased the abundance of microbial communities, especially propionate-utilizing bacteria and homoacetogenic bacteria.     

Comparison between acetate and propionate as carbon sources for phosphorus removal in the aerobic/extended-idle regime

Lately, we have proved that biological phosphorus (P) removal can be achieved in the aerobic/extended-idle (AEI) regime using glucose as the sole carbon source, which might develop a potential simple strategy for simultaneous removal of P and organic substrates from wastewater. Since acetate and propionate are the two most common substrates present in real domestic wastewater, this paper further assesses the P removal performances in the AEI process using acetate and propionate as the sole carbon source. The results showed that 3.91 and 3.64 mg of P/g of total suspended solids were, respectively, removed in the acetate-reactor and propionate-reactor after 50 days, respectively. After 90 days P removal in the propionate-reactor increased to 4.91 mg P/g of total suspended solids whereas that in the acetate-reactor kept in the same level (3.98 mg/g). Though both acetate and propionate could be used as carbon sources for P removal in such a novel system, the latter was more effective after long-term operation. Further investigations showed that, after 90 days’ acclimatization, sludge poly-P content in the propionate-system was more than that in the acetate-system, which was the primarily reason for the propionate-system showing higher P removal.     

Cyanobacterial biomass as N-supplement to agro-waste for hyper-production of laccase from Pleurotus ostreatus in solid state fermentation

The potential application of dry biomass of a cyanobacterium Anacystis nidulans as a supplement in SSF for the production of laccase from Pleurotus ostreatus was evaluated. Experiments were carried out in solid culture using groundnut shell as a basic substrate supplemented with four independent nitrogen sources (ammonium sulphate, urea, yeast extract and dry powder of cyanobacteria). All the four supplements enhanced the enzyme yield, and yeast extract showed precedence over inorganic nitrogenous sources. However, when dry biomass of A. nidulans was used as an additive to groundnut shell (agricultural residues), it supported maximum cell growth (56.83 ± 5.56 mg/g dry substrate) and laccase production (49.21 ± 4.89 U/g dry substrate). Addition of 1 mM copper salt in the medium containing groundnut shell supplemented with yeast extract gave laccase activity of 32.64 ± 3.4 U/g dry substrate. When dry powder of cyanobacterial biomass was used as N-supplement, laccase production enhanced to 65.42 ± 6.48 U/g dry substrate. In addition to the enhancement to enzyme production inhibitory effects of high concentrations of copper was also diminished in the medium having dry cyanobacterial biomass. This study, forms the first report on the potential application of cyanobacterial biomass as an additive for production of laccase by Pleurotus ostraetus MTCC 1804 in solid state fermentation and has relevance in scale-up production of this fungal enzyme of commercial significance.     

Dynamic simulation of a WWTP operated at low dissolved oxygen condition by integrating activated sludge model and a floc model

While an aeration tank in an activated sludge process is often operated with high dissolved oxygen (DO) concentration to ensure organic degradation and nitrification, it may be operated at low DO concentration to reduce energy consumption and achieve desired denitrification. The ASM1 (Activated Sludge Model No. 1) can be used to describe the activated sludge process if the nitrification and denitrification occur either during different phases or in different tanks, but it may encounter problems in simulating the denitrification phenomenon caused by low DO concentration in the aeration tank. In the present work, we developed a model integrating the ASM1 kinetics and a biofloc model to account for the actual anoxic and aerobic rates. Oxygen was assumed the only substrate of both bio-kinetically and flux limiting in the flocs and its dispersion coefficient was estimated as 1.2 × 10⁻⁴ m² day⁻¹ by using a set of measured effluent qualities of a full-scale wastewater treatment plant (WWTP) operating at low DO concentration (∼0.80 mg L⁻¹) for 60 days. Simulation studies predicted the optimal DO level of 0.36 mg L⁻¹ which would lead to minimum total nitrogen of 15.7 mg N L⁻¹ and also showed the insignificance of the addition of carbon source for nitrogen removal for the operation under study. The developed model may be helpful for process engineers to predict the plant behaviors under various configurations or operating strategies.     

Partial nitrification under limited dissolved oxygen conditions

Partial nitrification to nitrite is technically feasible and economically favourable, especially when wastewaters contained high ammonium concentrations or low C/N ratios. Partial nitrification can be obtained by selectively inhibiting nitrite-oxidizing bacteria (NOB) through appropriate regulation of the pH, temperature and dissolved oxygen (DO) concentrations. The effect of pH, DO levels and temperature on ammonia oxidation rate and nitrite accumulation was investigated in order to determine the optimal conditions for partial nitrification of synthetic wastewater with high ammonia concentration. The experiments performed at low DO levels to lower the total oxygen needed in the nitrification step, which means great saving in aeration. During the start-up stage pH and DO were set at 7.0–7.4 and 0.5 mg/l, respectively. The reactor was operated until complete partial nitrification was achieved. The effect of pH, DO on partial nitrification was studied, as pH was kept at 6.5, 7.5, 8.5, 9.5 and DO at 0.5±0.2, 1.5±0.2 and 2.5±0.2 mg/l, and temperature at 30 °C. The influence of temperature on k_a value was studied by keeping pH=7.5, DO=1.5 mg/l and temperature was controlled at 12, 20 and 30 °C, respectively. The results showed that partial nitrification to nitrite was steadily obtained and the optimal operational parameters were pH=7.5, DO=1.5 mg/l, T=30 °C based on ammonia oxidation rate and nitrite accumulation rate. The maximum k_a was achieved and to be 115.1×10⁻³ mg NH₄⁺–N (mg VSS h)⁻¹ under this condition.     

Optimization of biological treatment of paper mill effluent in a sequencing batch reactor

Laboratory scale research on the effects of operating parameters, including mixed liquor suspended solid (MLSS) concentration, volumetric exchange rate (VER), aeration time, temperature and daily operation cycle on biological treatment of the pulp and paper mill effluent was studied using four 4 l sequencing batch reactors (SBR). The results revealed that chemical oxygen demand (COD) removal efficiency was up to 93.1 ± 0.3% and the volumetric loading reached 1.9 kg BOD m⁻³ day⁻¹ under optimal operating conditions. The treatment performance of organic removal by the SBR system remained stable during the operation. The effluent quality was satisfied with the discharge standard set by the local authority and the filamentous bulking problem was solved. At the same time, the sludge settleability, in terms of sludge volume index (SVI), was improved to the healthy level (SVI = 52.7 ± 1.3 ml g⁻¹).     

Enhancement of asymmetric bioreduction of ethyl 4-chloro acetoacetate by the design of composition of culture medium and reaction conditions

This study investigated the feasibility of improving the stereospecificity of yeast by the adjustment of the culture medium composition and the reaction conditions. The investigation was performed systematically, using an approach that integrates the Taguchi's array method and the steepest ascent method. The reaction yield and the product's ee were the two indexes of reaction performance. A desirability function was applied to combine these two indexes as a single objective function. The removal of peptone and malt extract from the YM medium increased the yeast's stereoselectivity, without reducing the production of biomass. The medium composition and the reaction conditions were then simultaneously optimized. The resulting optimal conditions were 30 g/l glucose for cultivation, 12 g/l yeast extract, a cultivation time of 12 h, 15 g/l glucose for reaction, 150 g/l yeast for reaction, a reaction buffer concentration of 0.2 M and a buffer pH of 8.5. Compared to the one before this study, the product's ee was improved from 82.1 to 92.3%, and the reaction yield was enhanced from 77.3 to 82.3%. Furthermore, the biomass production was increased considerably from 5.94 to 10.14 g DCW/l.     

Abundance and biomass of planktonic ciliates in the sea area around Zhangzi Island,Northern Yellow Sea

We investigated the abundance and biomass of planktonic ciliates in the sea area around Zhangzi Island, Northern Yellow Sea, from July 2009 to June 2010. Ciliates were sampled monthly from surface to bottom with a 10 m depth interval at 13 sample stations along three transects. A 1 L sample of water from each depth was collected with a 2.5 L Niskin water sampler and fixed in 1% acid Lugol’s iodine solution. Water samples were pre-concentrated using the Utermöhl method and observed using an Olympus IX51 inverted microscope at 100× or 200x. The dimensions of the ciliates were measured and the cell volume of each species was estimated using appropriate geometric shapes. The carbon:volume ratio used to calculate biomass was 0.19 pg C/μm³. Abundance and biomass of the ciliate in water column were calculated as the integral of the abundance and biomass from bottom to surface, respectively. The classification of tintinnids was based on taxonomic literature. The average abundance of non-loricate ciliates was 3066 ± 2805 ind/L, ranging from 165 ind/L (50 m depth of St. B6 in July) to 26,595 ind/L (surface of St. C1 in September). The average biomass of non-loricate ciliates was 2.88 ± 2.68 μg C/L, ranging from 0.05 μg C/L (10 m depth of St. A6 in July) to 20.51 μg C/L (surface of St. A5 in August). The average tintinnid abundance was 142 ± 273 ind/L, ranging from 0 ind/L (monthly) to 2756 ind/L (surface of St. A1 in July). The average tintinnid biomass was 0.84 ± 2.19 μg C/L, ranging from 0.00 μg C/L (every month) to 37.64 μg C/L (20 m depth of St. C5 in July). The results showed that the average abundance of total ciliates was 3208 ± 2828 ind/L, ranging from 166 ind/L (10 m depth of St. A6 in July) to 26,625 ind/L (surface of St. C1 in September); the average biomass of total ciliates was 3.73 ± 3.55 μg C/L, ranging from 0.05 μg C/L (10 m depth of St. A6 in July) to 38.29 μg C/L (20 m depth of St. C5 in July). Abundance and biomass were vertically homogeneous in February, November and December, but decreased dramatically from the surface down to the bottom in other months. 23 tintinnid species were identified, 12 of which were in genus Tintinnopsis. Tintinnid species were more abundant in February, July and August. Tintinnids occupied 6.6 ± 10.2% and 19.7 ± 23.3% of the total ciliate abundance and biomass, respectively, which increased during the warm season and at coastal stations, and decreased during the cold season and at offshore stations. Large non-loricate ciliate species were prevalent in spring, while smaller species dominated in summer and autumn. The average abundance of total ciliates in water column was 132 ± 72 × 10⁶ ind/m², with increases during spring and autumn. The average biomass of total ciliates in water column was 152.57 ± 93.10 mg C/m², with increases during spring and summer. The average abundance and biomass of total ciliates in water column were greater at offshore stations than at coastal stations during spring and autumn, and were lower during summer and winter. Non-loricate ciliates, tintinnids and total ciliates showed significant positive correlation with temperature and significant negative correlation with salinity (p < 0.01). Non-loricate ciliates and total ciliates showed significant positive correlation with Chl a concentration (p < 0.01); however, relationship between Chl a concentration and tintinnids was not significant.