Initial Start-up Stage Research Articles

Study on the transient performance of textured water-lubricated bearings considering different acceleration conditions

This study analyses the transient friction dynamics behavior of water-lubricated bearings (WLBs) with a textured structure, which explains the mechanism of texture structure influencing the hydrodynamic effect of WLB in the physical aspect. A comparison of experimental and numerical data is carried out to validate the proposed mixed lubrication model with a textured structure for WLBs. The effects of texture type, texture angle, acceleration mode, and acceleration time on the nonlinear friction dynamics properties of WLBs are investigated. The result shows that various texture structures exhibit distinct pumping effects and that the optimal friction dynamics performance of WLBs can be achieved by adopting the right herringbone texture and an acceptable texture angle. It is advisable to utilize the reverse S-shaped acceleration mode, as it may efficiently mitigate hydrodynamic shock, minimize frictional contact at the initial startup stage, and control the rotor's vibration in later stages. The brief acceleration time may result in a transient shock that hampers proper lubrication, consequently affecting the stable operation of WLBs. The study's findings offer helpful suggestions for the enhanced design of WLB structures and the mitigation of wear and vibration.

Effects of different substrate ratios on the enrichment of anammox bacteria at low substrate concentration

Anammox bacteria (AnAOB) can be easily enriched under high temperatures and high substrate concentrations, while the application of the mainstream anammox process in low substrate municipal sewage is still relatively uncommon. Therefore, this study investigated the enrichment of AnAOB under conditions of low ammonia nitrogen and nitrite concentration at 25 °C. Results showed that using inoculated aerobic sludge, four ASBRs (R1, R2, R3 and R4) were successfully initiated with different influent substrate (NO2−-N/NH4+-N) ratios of 1.2, 1.32, 1.4 and 1.5, respectively, with reactor start-up times were 162, 150, 120 and 134 days, respectively. The values of ΔNO2--N/ΔNH4+-N in reactors were stable at 1.17, 1.32, 1.43 and 1.53 respectively. The increase in influent substrate ratios resulted in improved TN removal rates and accelerated consumption of chemical oxygen demand (COD) during the initial start-up stage. The maximum TN removal rates achieved in the four reactors were 76.09%, 79.24%, 82.82% and 82.63%, respectively. The color of sludge gradually changes from yellowish-brown to reddish-brown. Furthermore, the surface of sludge exhibited a porous mineral structure, with crater-like cavities. The dominant anammox species in the system was identified as Candida Brocadia (3.04%). According to qPCR, the abundance of hzsB in the system is 1.65 × 1012 copies/g VSS, confirming the effective enrichment of AnAOB.

Variations of flow patterns and pressure pulsations in variable speed pump-turbine during start-up process

Abstract In recent years, variable speed pumped-storage (VSPS) technology has become a hotspot of research and application due to its excellent power grid regulation capabilities. Since the speed of a VSPS unit is changeable, when switching operating conditions, more stable operating trajectories can be chosen to reduce vibration and damage. The simulations of transient processes of VSPS units normally use 1D method, which cannot judge the quality of operating conditions because of no flow pattern and pressure pulsation information. Using 3D CFD simulation based on OpenFOAM, we analyse the flow patterns and pressure pulsations when a VSPS unit with a full size frequency converter (FSFC) is in the turbine start-up process. The typical operating points in the variable speed transient trajectories obtained from 1D simulation are studied. It is found that in the initial stage of start-up, high-speed circulation flow arises in the vaneless space, leading to flow separation and large pressure pulsation. The results can provide a reference for the operation of VSPS power stations, so as to avoid operating conditions with adverse flow patterns and pressure pulsations.

Mechanisms of partial denitrification in an integrated fixed-film activated sludge (IFAS) system: From progressive startup to stabilization

The rapid startup and long-term stability of partial denitrification (PD) processes are essential prerequisites for successful PD/Anammox systems. Bioaggregates play a significant role in impacting mass transfer efficiency and shaping the microbial community structure within the PD process. Thus, the startup and stable operation of the PD process were investigated in an integrated fixed-film activated sludge (IFAS) by inoculating activated sludge and biofilm from anoxic tanks of a wastewater treatment plant. During the initial stage of startup, a sudden increase in NO3−-N concentration induced a rapid enzyme stress response, leading to a significant increase in total NaR activity (1.38 ± 0.0 μmol·(L·min)−1 to 25.94 ± 0.23 μmol·(L·min)−1), concomitant with the inhibition of total NiR activity (13.93 ± 0.48 μmol·(L·min)−1 to 4.25 ± 0.26 μmol·(L·min)−1), thereby inducing the rapid accumulation of NO2−-N (13.39 mg·L−1) within 6 days. During the later stage of startup, enzyme stress response was subsided but the partial denitrifiers were gradually enriched, consequently leading to continuous accumulation of NO2−-N. The results of ex-situ activity showed that flocs exhibit superior PD performance in contrast to biofilm throughout the entire operational period. Meanwhile, the total extracellular polymeric substances (EPS) content and community structure in both flocs and biofilm indicated that the migration of EPS-secreted partial denitrifiers (Thauera) from flocs to biofilm was obliged by substrate deficiency during the stable operating stage (days 35–100). Therefore, the startup of PD may be sequentially mediated by two distinct mechanisms, enzyme stress response and functional bacterial enrichment, with microbial community migration occurring during the stable phase.

Comparative study of two quick-analysis models for frozen startup of high-temperature heat pipes

The alkali-metal high-temperature Heat Pipe (HP) is the common component connecting the reactor core and energy conversion device in Heat Pipe cooled Reactor (HPR). Due to the particularity of the working medium, the frozen startup of HP makes a great influence on the startup process of HPR system. In this paper, two quick-analysis models, the Improved Thermal Resistance Network (ITRN) method and the Pseudo Wick Thermal Conductivity (PWTC) method have been investigated and compared. The simulations of a sodium HP in a typical experiment are carried out by two methods in COMSOL. For simulation speed, the convergence time of a single HP using the quick-analysis models is about tens to hundreds of seconds depending on the computing equipment. The convergence of PWTC is 26.7% faster than that of ITRN. For simulation accuracy, except for the inevitable error near the flat-front, the relative error of ITRN is less than 6.94% and the relative error of PWTC is less than 8.24%. The maximum effective error of ITRN method is 34.84 K, while that of PTWC method is 58.21 K at the initial stage of startup. The TTransition = 651 K in PWTC is lower than the Texp. = 710 K in the experiment and the TTr = 701 K in ITRN, which affects the accuracy at the initial stage of startup. The error will decrease gradually in the thawing front advancing stage. For simulation analysis, some inherent defects and targeted model improvements of the two models are proposed. Through the detailed comparative study in this work, researchers can easily apply the appropriate model according to the specific requirements and avoid the defects during the simulation process.

Field studies on indoor thermal environment and start-stop characteristics of the radiant air conditioning system during intermittent heating

With the improvement of social economy, the heating demand of residents in Hot Summer and Cold Winter (HSCW) areas in China is increasing. The radiant air conditioning (A/C) system, is popular as a heating way due to its high comfort, low noise and high energy saving potential. There is still a lack of field research on the system under the intermittent heating mode in the HSCW area. To provide a guide for the operation mode of the radiant A/C system during intermittent heating in HSCW areas, this paper focused on the radiant A/C system with the fresh air system, and then studied system's practical operational parameters and dynamic characteristics in winter. The indoor and outdoor air temperatures and relative humidity, the water temperatures of inlet and outlet of the air source heat pump (ASHP) unit, the supply and return water temperatures of radiant terminals, as well as supply air temperature were analyzed in three stages, i.e., the initial start-up stage, the intermittent shutdown stage and the intermittent start-up stage. The results show that, it took 7 h and 50 min for the indoor air temperature to reach the set indoor temperature during the initial start-up stage. Compared to the initial start-up stage, the intermittent start-up stage reduced the time for the indoor air temperature to reach the set indoor temperature by 4 h and increased the indoor air temperature rise rate by 97%. The indoor air temperature rise rate was 0.46 oC/h and 0.91 oC/h, during the initial start-up and the intermittent start-up stage, respectively. The indoor air temperature decrease rate was 0.23 oC/h during the shutdown period. During the entire winter season, the ASHP unit switched on and off intermittently 10 times. The longest shutdown lasted for 111 h, and the indoor air temperature dropped to 17.2oC.

Experimental and numerical studies of mode switching performance and water transfer in unitized regenerative fuel cells with different channel structures

Different flow channel structures of unitized regenerative fuel cells have great effects on the flow process of reactive gas, liquid product and flowing purge gas inside channels and the transport process of them in the porous media layer. In this study, the unitized regenerative fuel cell with three different kinds of channel structures are designed and manufactured based on the numerical simulation. By utilizing the unitized regenerative fuel cell testing set-up, the output electricity performance test of the single cell in the fuel cell mode, electrolytic cell mode and mode switching process are realized, and effective verification data are provided for the two-phase model verification of unitized regenerative fuel cells. The results show that different channel configurations result in various performance behaviors during different procedures of the cell. Using the channel having 1 mm square cross-section structures can perform better start-up performance, compared to the T-wide and T-narrow section channels. When entering into electrolysis cell mode, compared to the cell with T-section channels, the output performance of the cell constructed with 1 mm square section channel is decreased obviously at the initial stage of start-up because of the residual water affecting. The present experiments combined with simulation works facilitate better understanding how the performance and two-phase species changing at the operating procedures of unitized regenerative fuel cells with different flow channels.

Motion Characteristics of Collapse Body during the Process of Expanding a Rescue Channel

For the rapid construction of a rescue channel in the process of underground emergency rescue, a method for the expanded rescue channel in the collapse body is proposed and verified by a model test and a numerical simulation experiment. The motion characteristics and motion law of the expanded collapse body are analyzed on the basis of the mechanics of granular media, and a comparative simulation study on the main influencing factors of the collapse body motion is carried out. The results show that: (1) When the collapse body is expanded for a rescue channel, it will form three types of six relative slip planes. According to the position of the slip plane and the distribution of displacement, the collapse body can be divided into a direct displacement region, a stable region, and an indirect displacement region. (2) The expansion process can be divided into the initial start-up stage, the uplift stage, and the collapse stage, according to the formation time of the slip plane and the displacement law of the collapse body. (3) The results of the numerical simulation and the theoretical analysis of the granular media show that the dip angle of the slip plane is determined by the internal friction angle of the collapse particles, and the dip angles of the three slip planes are below θ1=90°−φ, θ2=45°+φ/2, and θ3=90°+φ/2. (4) The transverse scope and longitudinal distance is brought by the expansion increase with the increase in the expansion size, and the simulated dip angles of the slip plane are larger than the theoretical values due to the size effect. (5) In the expansion process, the strong force chain in the collapse body is concentrated in the stress arch above the expander device, and the failure and reconstruction laws of the stress arch at each stage are consistent with the formation of the slip plane and the uplift and instability law of the collapse body.

Comparative study on sequential and simultaneous startup performance of space nuclear power system with multi brayton loops

The closed Brayton cycle is an ideal energy conversion technology for high-power space nuclear power system (SNPS) because of its small volume, light weight, and stable operation. To increase the redundancy of the system, a SNPS with multi Brayton loops (SNPS-MBL) is adopted. Startup performance is an essential part of the off-design performance of SNPS-MBL. In this study, the thermal-hydraulic model of the SNPS-MBL was established. Two startup schemes, simultaneous startup and sequential startup, for SNPS with dual Brayton loops (SNPS-DBL) were formulated and the performance of the two schemes were compared. The results indicated that motoring power of external power source (EPS) was required to drive the rotation of the shaft at the initial startup stage. And the simultaneous startup of SNPS-DBL was stable and less time-consuming, but the motoring power of EPS was high; the motoring power of sequential startup scheme was less than that of simultaneous startup, but the coupling effect between Brayton loops led to the fluctuation of gas inventory and power in Brayton loop (BL), which is easy to cause the instability of the system. Furthermore, the influence mechanism of space environment temperature on sequential and simultaneous startup schemes were analyzed. The results showed that the environment temperature impacted the coupling effects of multi BLs during sequential startup. Elevated environment temperature redistributed coolant inventories between BLs during sequential startup and changed power of EPS and startup time of the two startup schemes. This study provides a reference for the design and operation of SNPS-MBL.

Influence of sea wave shock on transient start-up performance of water-lubricated bearing

The water-lubricated bearing in ship propulsion system is easily impacted by sea wave shock, which is a great threat to the smooth start-up of the bearing system. Therefore, in the present research, the Euler equations, average Reynolds equation, and sea wave shock function are combined together to build the start-up model of water-lubricated bearing. The influences of amplitude, direction, and entry time of sea wave shock on the start-up performance of bearing are studied. The result shows that the shaft has a strong instantaneous vibration under the influence of friction force at the initial start-up stage, and the shock load with appropriate direction and amplitude can suppress or even eliminate this vibration phenomenon. The earlier the shock enters the start-up process, the more serious asperity contact gets, and the worse the system’s stability becomes. The increase of the shock load amplitude and the advance of the shock load entry time can help the shaft rapidly lift off. This study can provide a reference for the smooth start-up of ship propulsion system in a sea wave environment.

Removal Efficiency and Mechanism of Ammonia Nitrogen in a Low Temperature Groundwater Purification Process

To explore the mechanism and efficiency of ammonia nitrogen removal, a pilot-scale biofilter for the simultaneous removal of high concentrations of iron, manganese, and ammonia nitrogen[Fe(Ⅱ) 11.9-14.8 mg·L-1, Mn(Ⅱ) 1.1-1.5mg·L-1, and NH4+-N 1.1-3.2 mg·L-1] from low temperature(5-6℃) groundwater was operated in a water supply plant in Northeast China. Results indicated excellent performance for ammonia nitrogen removal during the initial start-up stage. According to theoretical analysis and experimental verification, TNloss was driven by the adsorption of ammonia nitrogen by iron oxides, and the conversion of ammonia nitrogen into nitrate nitrogen occurred via biological nitrification. When the concentration of ammonia nitrogen increased, due to limited adsorption sites, the adsorption capacity of iron oxides remained stable at approximately 1 mg·L-1. For the same period, the amount of ammonia nitrogen removal via oxidation continued to increase, with higher quantities removed in the upper filter layer than in the lower filter layer. Dissolved oxygen(DO) is the limiting factor in the further increase in the removal of ammonia nitrogen by oxidation. With an increase in the filtration rate, the adsorption time of ammonia nitrogen by iron oxides was shortened, and the adsorption amount was reduced. Meanwhile, the shortening of EBCT reduced the ammonia nitrogen removed by nitrification under the action of nitrifying bacteria in the unit volume of the filter material. Based on these findings, it is recommended that the thickness of the filter layer should be increased to improve ammonia nitrogen removal performance.

Hormesis effects of sulfadiazine on aerobic granular sludge at decreasing temperature: Granulation, performance, microbial community and antibiotic resistance

Achieving stable granulation and operation at decreasing temperature has become a challenge for application of aerobic granular sludge (AGS). Antibiotic occurrence in wastewater may exacerbate the challenge, but relevant information is still lacking. Herein, we investigated whether and how the antibiotic sulfadiazine (SDZ) at different concentrations (0, 10, and 1000 μg/L in reactors RC, RL and RH, respectively) influencing AGS systems at seasonal temperature decrease from 25 to 10 °C. Results showed that all reactors experienced processes of granule formation, disintegration and recovery, and the SDZ had hormesis effects on AGS. Among the reactors, RL showed the fastest granulation and possessed the most stable granule structure, whereas RH obtained the slowest granule formation and had the severest granule disintegration. The SDZ exhibited low-level stimulation and high-level suppression on granule settleability, density and biomass, as well as nitrogen removal performance. Lower amount of extracellular polymeric substances (EPS) during initial start-up stage in RH could be related to the delay in granulation. While lower abundance of functional genera Nitrosomonas and Ca. Nitrotoga in RH could explain the deterioration in nitrogen removal. Metagenomic analysis further revealed higher abundances of resistome and mobilome in RH, mainly attributed to the enrichment of SDZ-corresponding resistance genes (sul1 and sul2) and transposases (tnpA), respectively. The abundance of sulfonamide resistance genes was mainly contributed by acquired antibiotic resistance genes (ARGs), indicating high potential for ARGs exchange in AGS microbes. This study provides novel insights into the effects of antibiotics on AGS at decreasing temperature.

Numerical study on suppression of thermoacoustic oscillation in cryogenic helium pipeline system

Suppression of gas oscillation is essential to realize the stable operation of the cryogenic helium piping systems. In the current study, a structural solution, that is, a tube is connected to the main pipe as an adjustment accessory to control unfavourable gas oscillations. The model with dual temperature gradients is developed by introducing an adjustment tube. The effects of the parameter sensitive to the distribution of the dual temperature gradients on the thermoacoustic oscillation (TAO) characteristics are revealed. The results demonstrate that the asymmetry of the temperature distribution and a large frequency deviation makes it easier to achieve the oscillation-free operation of the system. At the initial start-up stage, the phase relationship between the acoustic waves is shown. As the cold length to warm length ratio decreases, the phase difference between sound waves increases, and the oscillation-free operation is accomplished when the cold length to warm length ratio is 0.11. Therefore, an approach of adjusting the length ratio in the adjustment tube can control thermoacoustic oscillations of cryogenic fluid.

KINETICS OF EXCITATION OF A MAGNETIC FIELD IN ASYNCHRONOUS VALVE CASCADE

The essence of the physical processes of vector control of an asynchronous valve cascade (AVC), in particular the processes of excitation of a rotating magnetic flux, becomes clearer if this field is considered as an independent object. The nonlinearity of the system of differential equations of AVC prevents the separation and consideration of a rotating magnetic field as an independent physical object. For AVC, when the stator of asynchronous machine (AM) is powered from the network, and the rotor circuit – from the frequency converter, the problem of studying the process of creating a magnetic field was not considered. It is possible to substantiate the possibility of considering the dynamics of the magnetic flux isolated from the reaction of the active power channel, provided that the rotor is held stationary by the control system and the reactive current of the rotor is stabilized by its regulator at a certain level.
 The process of magnetization of AM in the circuit AVC is mainly due to the voltage of the supply network, which significantly limits the possibility of actively influencing the formation of the reference vector of the stator flux linkage with the help of the regulator of the reactive component of the rotor current. It becomes impossible to qualitatively control the electromagnetic torque AM at the initial stage of start-up, when the stator flux linkage takes on a steady-state value after prolonged oscillations. This phenomenon leads to the need to supply a reference signal to the speed control channel when the stator flux linkage vector reaches a steady-state value when the rotor is stationary and there is no load torque on the shaft. In the article, the task is to investigate the process of excitation of the magnetic field of the AVC and the influence of the current regulator on this process at its different structures in the reactive power channel. An original method of studying the statics and dynamics of excitation of the magnetic field of the AVC is applied, the results of which allow us to conclude that to increase the stability margin of the reactive power circuit of the AVC, it is necessary to regulate the magnetizing current in the control system of this circuit instead of the reactive component of the rotor current.

Combustion Adjustment in Initial Startup Stage of 660MW Supercritical Fossil Power Unit

In order to better improve economical efficiency, the newly built supercritical units mostly adopt more fuel-saving ignition mode, but in the initial startup stage, the parameters of unit and boiler are not compatible. This paper carries out study and analysis on parameters in the initial startup stage, and optimizes all parameters by adjusting startup feed-water quantity, fuel quantity, air volume and ratio for several times. With favorable effect, this paper may be used as good reference for other similar units.

Research on viscoelastic fluid unsteady flow model based on torque loss correction

To address the complexity of unsteady shear flow in the initial start-up stage of rheometers, a model considering torque losses in motors and fixtures was developed based on the true torque balance relationship at the rotor boundary of the rheometer and the constitutive equation of the viscoelastic rheological model. The viscoelastic fluid transient flow model was established, and the real wall stress expression of unsteady shear flow of the viscoelastic fluid in the initial stage was obtained. The reliability of the model was verified by comparing the result from the analytical model with numerical calculation. The impact of the geometric dimensions of the test system and the material viscoelastic characteristics on the transient test was analyzed. The results show that the non-uniform velocity distribution has little effect on the initial strain response in the gap of the actual test system of the rheometer. The oscillation curves of strain and stress obtained by numerical and analytical methods coincide completely, proving the reliability of the model in characterizing the transient flow. For a Jeffery fluid, the elastic modulus G mainly affects the oscillation period and amplitude, the parallel viscosity pots η1 mainly impact the amplitude and oscillation attenuation speed, and the series clay pots η2 mainly influence the slope of the strain curve. The greater the system inertia, the more significant the creep oscillation in the unsteady flow process. The coupling between the test system inertia and the viscoelasticity fluid is the essential cause of the creep oscillation. Combined with the mechanical response characteristics of rheometer, a Jeffery model based on short term correction and torque loss was established. The model can accurately describe the strain time curve of gelled crude oil in the initial unsteady flow stage. The results of this study can help understand the rheological properties of materials in the transient start-up process.

Process safety and environmental protection: An optimized solid phase denitrification filter by using activated carbon fibers for secondary effluent treatment

This study investigated the denitrification potential of an optimized solid-phase filter with activated carbon fiber (ACF) setting at the top and bottom under hydraulic retention time (HRT) shorter than 60 min from the synthetic secondary effluent. The results showed that, high nitrate removal efficiencies (>99 %) were obtained in reactors filled with poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) 3020 at initial stage of start-up. During stable operation under either HRT 40 min or 30 min, the reactor with PHBV 3020 as carrier achieved 90 %–100 % nitrate removal without nitrite accumulation. Moreover, it reached the maximum denitrification rates of 41.8 mg-N/Lh at HRT of 30 min which was significantly higher than that of the reactors filled by ACF/quartz grains and quartz grains at top and bottom. Microbial community in this reactor was dominated by the phylum Proteobacteria as well as Bacteroidetes. The ACF worked as favorable habitat for denitrifying bacteria Hydrogenophaga, Thiothrix, Desulfomicrobium and Sulfurimonas. The genera Ottowia, Limnohabitans, and Propionivibrio attached to ACF at top tended to degrade remaining organics. The optimized solid-phase denitrification filter with ACF showed good application potential for nitrate removal from the secondary effluent.

Study on the tribo-dynamic performances of water-lubricated microgroove bearings during start-up

In the present works, a tribo-dynamic model considering the transient friction force is proposed to study the tribo-dynamic performances of the Water-Lubricated Microgroove Bearings (WLMB) during start-up under three acceleration modes. Based on the developed model, the tribo-dynamic performances of WLMB between three bottom shapes, i.e. triangle, left triangle, right triangle, are compared. In addition, the effects of the key factors, including the acceleration time, bearing shell thickness, surface parameters and dry friction coefficient, on the tribo-dynamic performances of WLMB are identified. Numerical results demonstrate that at the initial stage of start-up, the transient horizontal friction force drives the rotor along the opposite direction of rotation. The comparative analysis indicates that the sinusoidal acceleration mode and left triangle bottom shape may be recommended to yield the optimal tribo-dynamic performances of WLMB during start-up. The parametric studies reveal that during start-up, the acceleration time and the surface roughness significantly affect the tribo-dynamic performances, whereas the asperity curvature slightly affects the tribo-dynamic performances. Furthermore, the numerical results demonstrate that the dry friction coefficient plays an important role in tribo-dynamic analysis for WLMB during start-up.

Logistics distribution mode analysis based on demand forecast

With rapid development of marketization in rural areas, the demand for logistics in rural areas, especially small-piece logistics for special agricultural products and daily necessities of farmers, has increased exponentially. Meanwhile, the supply of rural small-piece logistics cannot meet the demand over country. At present, postal companies and large private express delivery companies such as SF Express, YunDa Express, and ZhongTong Express are considered to be effective measures to alleviate the unbalanced situation, but their services do not satisfy markets in rural areas in three aspects: reasonable price, high efficiency and quality. In this paper, in order to establish a technically feasible and economically rational joint distribution mode, demand forecast for five counties in Hainan province is carried out based on time series model. Then two types of joint distribution mode are proposed based on the forecast using Logit model. Our results show that bus pick-up mode is suitable for initial start-up stage of rural small-piece logistics distribution projects, and logistics special-purpose vehicle distribution mode is suitable for mature stage of rural small-piece logistics projects.

The bacterial community significantly promotes cast iron corrosion in reclaimed wastewater distribution systems

BackgroundCurrently, the effect of the bacterial community on cast iron corrosion process does not reach consensus. Moreover, some studies have produced contrasting results, suggesting that bacteria can either accelerate or inhibit corrosion.ResultsThe long-term effects of the bacterial community on cast iron corrosion in reclaimed wastewater distribution systems were investigated from both spatial (yellow layer vs. black layer) and temporal (1-year dynamic process) dimensions of the iron coupon-reclaimed wastewater microcosm using high-throughput sequencing and flow cytometry approaches. Cast iron coupons in the NONdisinfection and UVdisinfection reactors suffered more severe corrosion than did those in the NaClOdisinfection reactor. The bacterial community significantly promoted cast iron corrosion, which was quantified for the first time in the practical reclaimed wastewater and found to account for at least 30.5% ± 9.7% of the total weight loss. The partition of yellow and black layers of cast iron corrosion provided more accurate information on morphology and crystal structures for corrosion scales. The black layer was dense, and the particles looked fusiform, while the yellow layer was loose, and the particles were ellipse or spherical. Goethite was the predominant crystalline phase in black layers, while corrosion products mainly existed as an amorphous phase in yellow layers. The bacterial community compositions of black layers were distinctly separated from yellow layers regardless of disinfection methods. The NONdisinfection and UVdisinfection reactors had a more similar microbial composition and variation tendency for the same layer type than did the NaClOdisinfection reactor. Biofilm development can be divided into the initial start-up stage, mid-term development stage, and terminal stable stage. In total, 12 potential functional genera were selected to establish a cycle model for Fe, N, and S metabolism. Desulfovibrio was considered to accelerate the transfer of Fe0 to Fe2+ and speed up weight loss.ConclusionThe long-term effect of disinfection processes on corrosion behaviors of cast iron in reclaimed wastewater distribution systems and the hidden mechanisms were deciphered for the first time. This study established a cycle model for Fe, N, and S metabolism that involved 12 functional genera and discovered the significant contribution of Desulfovibrio in promoting corrosion.