[Rapid Start-up of Continuous Autotrophic Nitrogen Removal Reactor by Hybrid-inoculating PN and PN/A Granular Sludges].

The rapid cultivation of partial nitritation/ANAMMOX （PN/A） granular sludge in a continuous-flow mode is one of the key technologies for efficient biological nitrogen removal in domestic wastewater treatment. Compared with that in PN/A granular sludge, PN granular sludge demonstrates a shorter incubation period and suitability for batch culture. It is also a good carrier for enriching ANAMMOX （AMX） bacteria. In this study, we established a continuous-flow autotrophic nitrogen removal process in three continuously stirred tank reactors （CSTR） （R1-R3） by hybrid-inoculating PN/A and PN granular sludge at the mass ratios of 3∶1, 1∶1, and 1∶3, respectively. By implementing high ammonium nitrogen loading and short hydraulic retention time, continuous autotrophic nitrogen removal processes were successfully started up in the three CSTRs. The results showed that compared with that of R1 and R2, R3 had a longer start-up time but a similar steady-state nitrogen removal performance. The total nitrogen removal load of R3 could be more than 2.6 kg·ï¼ˆm3·d）-1. Intriguingly, the inoculated PN granular sludge served as a precursor for PN/A granular sludge cultivation. This approach facilitated the enrichment of anaerobic ammonia-oxidizing bacteria （AMX） by introducing abundant ammonium-oxidizing bacteria （AOB） and nitrite nitrogen substrates into the CSTR. According to the results of high-throughput sequencing, the microbial abundance and diversity of the mature granules in R1-R3 were significantly higher than those of the inoculation sludge. AOB （genus Nitrosomonas）, AMX （genera Candidatus Kuenenia and Candidatus Brocadia）, and symbiotic heterotrophs, such as Chloroflexi, Bacteroidetes, and Chlorobi, drove the autotrophic nitrogen removal process and maintained the stability of the granular structure. In summary, a novel start-up strategy of hybrid-inoculating granular sludge was provided for a continuous-flow autotrophic nitrogen removal in engineering application.

[Effects of Cold Acclimation on the Activity of Autotrophic Nitrogen Removal in Granular Sludge and Its Bacterial Population Structure].

Cold acclimation is an effective approach for improving the nitrogen removal performance and operational stability of partial nitritation/ANAMMOX (PN/A) combined processes at low temperatures. To explore the specific effects of cold acclimation on the characteristics of sludge, differentiations in temperature sensitivity, granular morphology, composition of extracellular polymer substance (EPS), and bacterial community structure between PN/A granular sludges cultivated at medium-high temperature (30℃) and acclimated to low temperature (15℃) were investigated in this study. The results of reaction thermodynamics showed that the nitrogen removal performance of the granules acclimated to low temperature (GL) was significantly higher than that of those cultivated at medium-high temperature (GH) under the low temperature (10-20℃), and the apparent activation energy (Ea) of total inorganic nitrogen removal for the former was decreased by 28.4%. Compared with GH, GL had a smaller average particle size of 25.8% and higher EPS contents of 16.6%, resulting in a significant lower settling property. Based on the high-throughput sequencing results, GL exhibited a higher diversity of bacterial community, and a lower relative abundance ratio (0.04) of aerobic ammonium-oxidizing bacteria (Nitrosomonas) and anaerobic ammonium-oxidizing bacteria (Candidatus_Kuenenia) than 0.34 for GH. It indicated that the PN/A granules held a strong ability to retain slow-growing autotrophic bacteria in the system, even under low temperatures. These findings could provide meaningful references for analyzing the self-adaption mechanisms of PN/A sludge to low temperature conditions and promote the industrial application of combined processes.

[Performance and Microbial Characteristics of Ammonium-limited and Nitrite-limited ANAMMOX Systems].

The performance and microbial characteristics of ammonium-limited and nitrite-limited ANAMMOX reactors were studied in two continuously stirred tank reactors. The influent TN concentrations were controlled below 50 mg·L-1. The hydraulic retention time and water temperature were maintained at 2.0 h and 20℃, respectively. Results showed that though both ANAMMOX reactors demonstrated similar TN removal loading rates[0.45-0.5 kg·(m3·d)-1] and TN removal efficiencies (around 70%), the ΔNO3-/ΔNH4+ ratio of the ammonium-limited ANAMMOX reactor showed a faster upward trend. Batch tests and high-throughput sequencing results indicated that the ammonium-limited ANAMMOX reactor had more significant functional and population heterogeneity than the nitrite-limited ANAMMOX reactor. Candidatus_Brocadia was the predominant ANAMMOX bacteria in both reactors. The relative abundance of Candidatus_Brocadia in large granules (53.9%) was significantly higher than that in flocs (19.1%) under the ammonium-limited conditions, whereas only a small difference in relative abundance of Candidatus_Brocadia was observed between the granules (28.1%) and flocs (21.3%) in the nitrite-limited ANAMMOX reactor. Nitrospira-like NOB were detected in both ANAMMOX reactors, which primarily inhabited flocs, seemingly driven by the availability of oxygen. Moreover, the ammonium-limited (i.e., excess nitrite) conditions seemingly favored the growth of Nitrospira. Building upon these results, a control strategy for optimal operation of the ammonium-limited ANAMMOX reactor was proposed based on selective floc discharge.

[Start-up and Optimization of Denitrifying Phosphorus Removal in ABR-MBR Coupling Process].

The feasibility of the denitrifying phosphorus removal process in the ABR-MBR system with no sludge reflux and high concentration of seeding activated sludge (25 g ·L-1, in MLSS) in the ABR was investigated. The characteristics of the microbial community in the denitrifying phosphorus removal compartment were also evaluated. The denitrifying phosphorus removal function was achieved by gradually increasing the reflux ratio (R) from 0% to 200%. During the stable operation, the average removal rates of COD, PO43--P, and TN in the system were 88.28%, 54.45%, and 61.93%, respectively. When the influent loading rate, NOx--N reflux ratio, and hydraulic retention time (HRT) of ABR and MBR were 0.8 kg ·(m3 ·d)-1, 150%, and 9 h and 3.3 h, respectively, the average VFA concentration of 80.58 mg ·L-1, ρ(NO2--N)/ρ(NO3--N) reflux ratio of 1.68, and PO43--P and TN removal rates of 64.94% and 62.95% were obtained. The short-cut nitrification denitrifying phosphorus removal was achieved in the ABR-MBR system. Batch tests showed that denitrifying phosphorus removal bacteria (DPAOs) were the main functional bacteria in the ABR, with anaerobic phosphorus release and anoxic phosphorus uptake of 3.73 mg ·L-1 and 10.22 mg ·L-1, respectively. High throughput sequencing results showed that Proteobacteria and Bacteroidetes were the dominant phyla in the phosphorus removal compartment, accounting for 23.49%-53.66% and 16.55%-21.78% of the total phyla, respectively. Thauera, Thiothrix, Pseudomonas, norank_ f_Rhodocyclaceae, and unclassification_ f_Rhodocyclaceae in Proteobacteria, and Sphingobacteriales in Bacteroidetes were the potential denitrifying phosphorus removal microorganisms.

[Impact of Hydraulic Retention Time on Performance of Partial Nitrification Granular Sludge in Continuous Stirred-Tank Reactor].

The effects of different hydraulic retention time (HRT) on short-cut nitrification granular sludge were studied in a continuous stirred-tank reactor (CSTR) by maintaining stable influent ammonia nitrogen load. Particle size distribution, extracellular polymeric substances (EPS), and functional bacterial kinetics were analyzed. The morphology of granular sludge, the performance of the CSTR, and the activity of functional microorganisms were investigated. The high throughout sequencing technology of MiSeq was employed to analyze the structure of the microbial community in sludge. The results showed that the ammonia nitrogen removal rate in the reactor was gradually increased from 80% to 95%, and the nitrite accumulation rate was always over 85% when the HRT was decreased from 4 h to 1 h. Particle size distribution of granular sludge was greatly influenced by HRT. The mass fraction of granules with a diameter smaller than 0.3 mm and larger than 1.6 mm was gradually declined, whereas the mass fraction of granules with a diameter between 0.3 mm and 0.8 mm was increased when HRT was shortened from 4 h to 1 h. The dominating proportion of granules with a diameter between 0.3 mm and 0.8 mm reached about 50% when HRT was 1 h. The impact of HRT on the activity of functional microorganisms was studied, and HRT activity was found to be closely related to the size of granular sludge. Proteobacteria were dominant in the system. AOB enrichment was represented by Nitrosomonas, which was more than 56%. Shortening HRT is beneficial for the enrichment of AOB.

[Realization Process of Nitritation and Changes in Sludge Characteristics in Granular Sludge Reactor for Low Strength Sewage Treatment].

The realization process of nitritation was studied in a CSTR reactor seeding with nitrification granular sludge to treat low ammonia sewage. During the operation period, the physical and chemical properties, the spatial distribution of functional microbes, and the activity of the granular sludge were also investigated to elaborate the main factors for the stability of nitritation. The results showed that nitritation can be successfully achieved and maintained by the cooperative controlling of nitrogen loading rate (NLR) and dissolved oxygen (DO) levels, and the nitrite accumulation rate was over 80%. The obtained nitritation granular sludge was brownish yellow, showing a smooth, full ellipsoid or sphere, and the microorganisms on the surface of the particles were mainly cocci; the average particle size was 1.3 mm, and the average sedimentation rate was 71.3 m·h-1. Batch tests showed that there was a significant stratified distribution structure in granular sludge (particle size >0.8 mm), the ammonia-oxidizing bacteria (AOB) mainly occupied the surface space of the particles, and the nitrite-oxidizing bacteria (NOB) were mainly distributed inside the particles. Flocs or small-size sludge (particle size<0.8 mm) and granular sludge (particle size >0.8 mm) exhibit different spatial distribution characteristics of microorganisms. In the granular sludge reactor, well stratification of the nitrifier guilds, high level of residual ammonia concentrations in effluent (15-33 mg·L-1), or low ratio between DO and NH4+-N concentrations (0.08-0.15) should be key influencing factors in the process of achieving nitritation.

[Characteristics of Organics Transformation and Sludge Morphology in an ABR for Sewage Treatment with Different HRTs].

The characteristics of organics transformation and sludge morphology of in an ABR(anaerobic baffled reactor) for sewage treatment with different HRTs were investigated based on reactor performance, particle size distribution, and scanning electron microscopy (SEM). Results showed that the COD removal rate was stably maintained above 90.0% when the HRT decreased from 15 h to 4 h. However, the first compartment of ABR contributed to 90%, 78.56%, 74.18%, and 58.91% of the total COD removal when the HRT was 10, 7.5, 5, and 4 h, respectively. When the HRT was reduced, the total amount of volatile fatty acids (VFAs) in the first compartment of ABR significantly increased, and the abundance of acetic acid, being the major constituent of VFAs, gradually increased from 51.36% to 58.77%; the concentrations of butyric acid and propionic acid were maintained and constituted a minority of the VFAs. The sludge morphology in ABR significantly changed in the wake of run time. On day 111, granulation of sludge was achieved. Additionally, the degree of sludge granulation showed a decreasing trend with the direction of water flow. SEM observations of granular sludge showed that the separation of biomass did occur in the ABR. Along the direction of water flow, filamentous bacteria, M. methane, monococci, and bacilli were the dominant microbes in each compartment of the ABR.

[Rapid Achievement of Nitrifying Micro-granular Sludge and Its Nitritation Function].

The rapid achievement of nitrifying micro-granular sludge and its nitritation function was studied in a continuously operated internal-loop airlift reactor seeding with floccular sludge. Results showed that the sludge micro-granulation was almost realized within three weeks by gradually reducing the hydraulic retention time from 5 h to 2.5 h. The color of the sludge first changed from yellowish-brown to creamy white, and then changed to pale yellow during the micro-granulation process. The settleability of the sludge first changed from good to bad, and then recovered to good. The value of the sludge settling velocity (SV) at SV5 and SV30 were both equal to 4%-5%, while SVI30 and SVI5 were both around 12-13 mL·g-1. The average size of the obtained nitrifying micro-granular sludge was 134 µm on day 27. Nearly 70% of the nitrifying micro-granular sludge was maintained in a relatively narrow range of 59-163 µm, thus indicating the largely homogeneous diameter distribution of these micro-granules. After sludge micro-granulation, the nitritation function was achieved within one week by progressively increasing the influent NH4 concentrations from 50 mg·L-1to 200 mg·L-1. The NO2- accumulation ratio and the nitritation loading rate reached up to 90% and 1.34 kg·(m3·d)-1, respectively. The high level of residual NH4 concentration in the effluent, or the low ratio of dissolved oxygen (DO) to NH4+-N concentrations (0.03-0.09), should be the primary cause of the rapid achievement of nitritation in the micro-granular sludge reactor.

[Start-up and Stable Operation of CANON Coupled with Denitrifying Phosphorus Removal].

A process coupled completely autotrophic nitrogen removal over nitrite (CANON)with denitrifying phosphorus removal in a modified anaerobic baffled reactor (ABR) coupled with a membrane bioreactor (MBR), inoculated with ordinary activated sludge, was proposed for treating artificial wastewater with ammonia 200 mg·L-1 and COD/TN=1. This experiment studied the start-up of the process and its nitrogen and phosphorus removal efficiency by controlling the recycle ratio and increasing it from 50% to 200% step by step, with a temperature of (25±1)℃ and pH of 7.5±0.2. The results showed that the anaerobic part in the ABR consumed 70% COD, and resulted in a quick start-up of partial-nitrification at 21 d under low DO and high ammonia nitrogen. Then, by controlling the intermittent aeration (exposure stop ratio:2 h:2 h, DO 0.3-0.4 mg·L-1), the start-up of the CANON part in the coupling process was successfully achieved at 132 d, such that the concentration of nitrates in the electron acceptor of the ABR anoxic section increased steadily, and finally the coupling process started successfully at 160 d. With stable operation, the TN removal load in the MBR reached 0.22 kg·(m3·d)-1, and the average removal efficiency of COD, TN, and PO43--P was 87.0%, 90.4%, and 81.8%, respectively. The batch experiment estimated that the denitrifying phosphate accumulating organisms (DPAOs) using nitrates as electron acceptors in the ABR accounted for 68% of the phosphate accumulating organisms (PAOs). The DPAOs, ammonia-oxidizing bacteria (AOB), and anaerobic ammonium oxidizing bacteria (AnAOB) have been developed in the system and have good simultaneous nitrogen and phosphorus removal efficiency.

[Comparison of the Microbial Community Structure in Nitrifying Processes Operating with Different Dissolved Oxygen Concentrations].

High-throughput sequencing was applied to analyze the microbial community structure of nitrifying reactors operated with different dissolved oxygen (DO) levels. Results showed that the nitrifying reactor (RL) run with low DO (0.2-0.3 mg·L-1) exhibited greater microbial richness and diversity than the reactor run under the high DO condition[RH, DO=(2.0±0.1) mg·L-1]. In contrast, the microbial community in RH was more highly functionally organized than that in RL. Although the communities in RH and RL shared over 85% of the total sampled genetic information, the relative abundance of some individual species varied between the different DO conditions. Members of the Proteobacteria phylum, which accounted for 80.7% of the total microbes in RH, were highly enriched, and the relative abundance of Nitrosomonas reached to 65.1%. However, the microbial community in RL was dominated by Proteobacteria (43.8%), Firmicutes (20.0%), and Bacteroidetes (15.1%). In addition, a large fraction of bacteria possessing hydrolyzation and fermentation functions under anaerobic or anoxic conditions were also present in RL including Lactococcus, Anaerolineaceae, and Rhodocyclaceae. As known ammonium-oxidizing bacteria, Nitrosomonas oligotropha and Nitrosomonas europaea were enriched in the RH and RL, respectively, while Nitrospira defluvii, being a nitrite-oxidizing bacteria, dominated both reactors. Rather than DO, ammonia and nitrite availability should be key factors in the selective enrichment of these nitrifiers.

[Effect of Sludge Retention Time and pH on the Denitrifying Phosphorus Removal Process].

In this work, the effects of the sludge retention time (SRT, 35, 25, or 15 d) and pH (7.5, 8.0, 8.5) on denitrifying phosphorus removal were investigated using denitrifying phosphorus bacteria (DPBs) enriched in a sequencing batch reactor (SBR). The results indicated that shortening the SRT from 35 d to 25 d resulted in a decrease in the mixed liquor volatile suspended solids (MLVSS) from 2821 to 2301 mg·L-1, while the sludge loading rate (F/M) increased from 0.256 kg·(kg·d)-1to 0.312 kg·(kg·d)-1. Although the quantity of net phosphorus release and net phosphorus uptake decreased at this stage, the rates of anaerobic phosphorus release, anoxic phosphorus absorption, and denitrification reached their highest levels with values of 25.07, 15.92, and 9.45 mg·(g·h)-1, respectively, due to the increased sludge activity. Consequently, the phosphorus content of the sludge increased from 4.78% to 5.33%, and the removal rate of PO43--P was stable at above 95% with an average effluent PO43--P concentration below 0.5 mg·L-1. When the SRT was further shortened to 15 d, the MLVSS decreased to values as low as 1448 mg·L-1, and the proportion of DPBs in the phosphorus accumulating organisms (PAOs) decreased from 82.4% to 65.7%, indicating that the DPBs were gradually washed out from the system due to the excessively short SRT. At this stage, the phosphorus content of sludge decreased to 3.43%, while the rates of phosphorus release, phosphorus absorption, and denitrification also decreased to some extent. When the pH was increased (7.5-8.0), the anaerobic phosphorus release rate and the anoxic phosphorus absorption rate also increased, and reached 25.86 mg·(g·h)-1 and 16.62 mg·(g·h)-1, respectively, at a pH of 8.0. When the pH exceeded 8.0, the phosphorus removal efficiency dropped rapidly, supposedly due to phosphorus chemical precipitation.

[Start-up and Stable Operation of ABR-MBR Denitrifying Phosphorus Removal Process].

The nitrogen and phosphorus removal characteristics during the start-up and the long-term operational stability of an anaerobic/anoxic (A/A) ABR coupled aerobic MBR system treating low C/N domestic wastewater were investigated. The results showed that the denitrifying phosphorus bacteria (DPBs) were successfully enriched within 46 d by controlling the nitrate recycling ratio (increasing from 150% to 300%), with a temperature of 30℃±2℃, volume loading rate of 0.8 kg·(m3·d)-1 and sludge reflux ratio of 80% in the ABR, sludge retention time (SRT) in the denitrifying phosphorus removal functional area of 25 d, and the dissolved oxygen (DO) of 1-2 mg·L-1 in the MBR. The net phosphorus release and phosphorus uptake of DPBs reached 20.56 mg·L-1and 27.74 mg·L-1, respectively. Batch tests demonstrated that about 84.8% of phosphorus-accumulating organisms (PAOs) could use NO3--N as an electron acceptor for denitrifying phosphorus removal. After 50 d of stable operation after the successful system start-up, the average removal rates of COD, NH4+-N, TN, and PO43--P were 91.8%, 99.0%, 71.5%, and 94.2%, respectively. The results also suggested that 0.83 mg·L-1NO3--N was consumed per 1 mg·L-1 PO43--P removed during the denitrifying phosphorus removal, indicating that the simultaneous nitrogen and phosphorus removal was achieved in the ABR-MBR system.

[High-rate Nitrogen Removal in a Two-stage Partial Nitritation-ANAMMOX Process Under Mainstream Conditions].

A two-stage partial nitritation (PN)-ANAMMOX process was successfully carried out for low-strength NH4+-N (50 mg·L-1) wastewater treatment at ambient/low temperatures. The results show that an average total nitrogen removal rate and removal efficiency above 0.6 kg·(m3·d)-1and 80% could be maintained, respectively, at temperatures between 20℃ and 14℃. The two-stage PN-ANAMMOX process was successful both under NO2--N-limited and NH4+-N-limited conditions. When the two-stage PN-ANAMMOX process was operated under NH4+-N-limited conditions, the "limit of technology" for nitrogen removal (TN<3 mg·L-1) could be easily achieved by following anoxic denitrification. Lowering the temperature to 12℃ resulted in the reduction of the total nitrogen removal rate to~0.5 kg·(m3·d)-1. Due to the low temperature, the anammox reaction became the rate-limiting step for nitrogen removal, while the PN reaction was not impacted. In the temperature range of 10-20℃, the activity-temperature coefficients (θ) of the PN granules and ANAMMOX sludge were 1.056 and 1.172, respectively, suggesting that the anammox bacteria have a higher temperature sensitivity than the ammonium oxidizing bacteria (AOB). Overall, the results clearly indicate that the nitrogen removal loading rate of the two-stage PN-ANAMMOX process is mainly controlled by the activity and quantity of anammox biomass. In contrast, the process nitrogen removal efficiency mainly depends on the performance of the first-stage PN (i.e., effluent NO2--N/NH4+-N ratio and NO3--N concentration) under a constant nitrogen removal loading rate (no overload). Based on these results, a hierarchically separate control strategy was proposed to obtain a high-rate nitrogen removal during the two-stage mainstream PN-ANAMMOX process.

[Effects of anaerobic feeding period on nitrifying granular].

Alternating anoxic/oxic conditions have profound effects on both ammonium (AOB) and nitrite (NOB) oxidizing bacteria. In this study the influence of alternating anoxic/oxic condition on nitrifying granules was evaluated in a laboratory-scale column-type sequencing batch reactor (SBR). The anoxic phase was extended from 10 min to 120 min by increasing the anaerobic feeding time. Granules maintained their structure and characteristics during the whole study. The amount of granules with diameter larger than 0.8 mm kept above 95% (mass fraction), and the average settling velocity of particles maintained in the range of 125-130 m x h(-1). Despite the increase in the length of anoxic phases, the values of ammonium removal and nitrite accumulation in effluent still kept at (60 +/- 5)% and (85 +/- 5)%, respectively. Moreover, in the aeration period per cycle, NH4(+) -N removal loading rates, NO2(-) -N and NO3(-) -N accumulation loading rates retained stably at 90 mg x (L x h)(-1), 70 mg x (L x h)(-1) and 15 mg x (L x h)(-1), respectively. All these results suggested the changing anoxic conditions resulted from prolonged anaerobic feeding period had no significant effects on nitrifying granules.

[Research on change process of nitrosation granular sludge in continuous stirred-tank reactor].

In order to investigate the effect of different types of reactors on the nitrosation granular sludge, a continuous stirred-tank reactor (CSTR) was studied, using mature nitrosation granular sludge cultivated in sequencing batch reactor (SBR) as seed sludge. Results indicated that the change of reactor type and influent mode could induce part of granules to lose stability with gradual decrease in sludge settling ability during the initial period of operation. However, the flocs in CSTR achieved fast granulation in the following reactor operation. In spite of the changes of particle size distribution, e. g. the decreasing number of granules with diameter larger than 2.5 mm and the increasing number of granules with diameter smaller than 0.3 mm, granular sludge held the absolute predominance of sludge morphology in CSTR during the entire experimental period. Moreover, results showed that the change of reactor type and influent mode didn't affect the nitrite accumulation rate which was still kept at about 85% in effluent. Additionally, the average activity of the sludge in CSTR was stronger than that of the seed sludge, because the newly generated small particles in CSTR had higher specific reactive activity than the larger granules.

[Study on rapid start-up of a nitrifying process using aerobic granular sludge as seed sludge].

Using synthetic ammonia-rich wastewater as influent, rapid start-up of the nitrification reactor was attained in a laboratory-scale column-type sequencing batch reactor (SBR) inoculated with aerobic granular sludge, by gradually increasing the influent NH4(+) -N concentration (100-1000 mg x L(-1)) and decreasing the hydraulic retention time (8-4 h) under mesophilic condition (28-30 degrees C). The influent loading rate of NH4(+) -N reached 3.9 kg x (m3 x d)(-1) and the average ammonia removal efficiency was above 95% within one month. Values of ammonia oxidizing rate (AOR) as high as 5.0 kg x (m3 x d)(-1) was obtained in the following operational stage with extremely high nitrogen loading rate. Nitrite accumulation obviously occurred during the start-up period. The nitrite accumulation rate reached 2-4.5 kg x (m3 x d)(-1) from day 25 to 70. In spite of the change in the feeding composition (COD/N ratio) and the frequent fluctuations of nitrogen loading rate, the granules maintained their structures, with the SVI of 30-40 mL x g(-1). The amount of granules with diameter larger than 0.21 mm was about 93% (mass fraction) of the total on day 36. The granular color changed from yellow to brownish-yellow, and some turned brown in this study. All these results suggested the critical role of aerobic granular sludge as seed sludge for the rapid start-up of nitrifying processes and the formation of nitrifying granules.

[Alteration of anterior chamber and angle structure in eyes with primary angle closure after laser peripheral iridotomy].

OBJECTIVE: To quantitatively evaluate the long-term changes in anterior segment morphology by using ultrasound biomicroscopy (UBM) after laser peripheral iridotomy (LPI) in eyes with primary angle closure (PAC). METHODS: This was a clinical case series study. A total of 54 eyes with PAC of 31 consecutive patients were enrolled. Routine ophthalmic and UBM examination were performed at visit one (before LPI), 2 weeks, 6, and 12 months after LPI. The parameters of anterior chamber were measured by UBM and calculated. Results of each follow-up time were analyzed using repeated measures analysis of variance. Parameters of UBM measurement at 750 µm anterior to the sclera spur and at 500 µm counterpart were compared using paired student t-test. RESULTS: Compared to before LPI, anterior chamber depth (ACD) was deepened by approximate 0.10 mm after LPI, however, it was not statistically significant (F = 3.50, P > 0.05). Angle opening distance (AOD), trabecular-iris angle (TIA), angle recess area (ARA) and trabecular-ciliary process distance (TCPD) were significantly increased at 2 weeks, 6 and 12 months after LPI compared with respective baseline [AOD750: (165.0 ± 70.3), (185.8 ± 68.5), (196.1 ± 77.7) µm vs (66.2 ± 51.6) µm, F = 92.60; TIA750: 14.1° ± 6.3°, 15.5° ± 6.2°, 16.4° ± 5.9° vs 6.4° ± 4.9°, F = 92.60; ARA: (0.058 ± 0.024), (0.065 ± 0.023), (0.068 ± 0.026) mm(2) vs (0.025 ± 0.017) mm(2), F = 92.60; TCPD: (647.1 ± 113.0), (701.8 ± 93.4), (670.1 ± 95.4) µm vs (571.0 ± 97.2) µm, F = 34.00; P < 0.05]. The parameters of UMB measurement at 750 µm were significantly increased more than that at 500 µm anterior to the sclera spur (AOD: t = 5.90, TIA750: t = 2.70, P < 0.05; ARA: t = 2.00, P = 0.05). CONCLUSIONS: LPI can significantly widen the peripheral anterior angle in eyes with PAC lasting for at least 1 year after LPI. Parameters detected by UBM at 750 µm anterior to the sclera spur appear to be more sensitive in evaluating the alternation of peripheral angle structure.

Laser peripheral iridotomy with and without iridoplasty for primary angle-closure glaucoma: 1-year results of a randomized pilot study.

PURPOSE: To compare the efficacy and safety of laser peripheral iridotomy with or without laser peripheral iridoplasty in the treatment of eyes with synechial primary angle-closure or primary angle-closure glaucoma. DESIGN: Randomized, controlled clinical trial. METHODS: Consecutive patients older than 40 years with synechial primary angle-closure or primary angle closure glaucoma were recruited. Eligible patients were randomized to 1 of 2 treatment options, iridotomy or iridotomy plus iridoplasty, and were followed up for 1 year. Main outcome measures were intraocular pressure (IOP), peripheral anterior synechiae, corneal endothelial cell count, and complications. RESULTS: Seventy-seven eyes (77 patients) were randomized to the iridotomy group, and 81 eyes (81 patients) were randomized to the iridotomy plus iridoplasty group. Sixty-one patients (79.2%) in the iridotomy and 65 patients (80.2%) from the iridotomy plus iridoplasty groups completed 1 year of follow-up. There were no significant differences between the groups in the baseline data. IOP was reduced from 24.66 +/- 13.76 mm Hg to 19.03 +/- 6.21 mm Hg in the iridotomy group (P < .001) and from 27.96 +/- 13.06 mm Hg to 20.45 +/- 7.26 mm Hg in the iridotomy plus iridoplasty group (P < .001). Extent of peripheral anterior synechiae was decreased by 1 more clock-hour after iridoplasty compared with that after iridotomy in the iridotomy plus iridoplasty group (P < .001). There was no significant difference in IOP, medications, need for surgery, or visual function between groups at the 1-year visit. CONCLUSIONS: In eyes with synechial primary angle-closure or primary angle-closure glaucoma, both iridotomy alone or combined with iridoplasty provide a significant and equivalent reduction in IOP. There is also a possible reduction in peripheral anterior synechiae, more so in the iridoplasty group.