Effect of seeding biofloc on the nitrification establishment in moving bed biofilm reactor(MBBR)

In recirculating aquaculture systems,nitrification is usually accelerated by inoculating nitrifier or mature biocarriers.In this study,the performance of the establishment of nitrification in the MBBR according to three different strategies:conventional method(Control group A),inoculation with biofloc recovered from a tilapia biofloc culture system(Group B),and addition with extra nitrite(Group C)in the Moving bed biofilm reactor(MBBR)was compared.Among them,the biofloc-inoculated group considerably accelerated the nitrification process in the MBBR(38 d),which is roughly 18 d faster than the control group(A)(56 d)and 21 d faster than group C(59 d).Less ammonia(8 mg/L NH_(4)^(+)-N,10 mg/L in other groups)and external nitrite(2 mg/L NO_(2)􀀀^(-)N)in the influent caused effluent ammonia to drop more slowly(5 d slower than the control group,8 d slower than the B group),which is detrimental to the nitrification process’development.Notably,the influent’s hydraulic retention time(HRT)was reduced from 12 h to 6 h following the successful establishment of nitrification.During the adaptation to reduced HRT,the MBBR inoculated with biofloc experienced short-term changes in the water quality index of the effluent water,whereas the other groups did not.The biofilm seeded with biofloc had the highest mean gray value ratio(1.42)of live/dead cell fluorescence,which grew better and could cover the entire groove under multiple microscope observations.However,the other groups did not demonstrate a similar trend.In summary,the research found that seeding biofloc use as nitrification bioaugmentation into the MBBR of the recirculating aquaculture system(RAS)to greatly speed up the nitrification process.

Inhibition and recovery of nitrification in treating real coal gasification wastewater with moving bed biofilm reactor

Moving bed biofilm reactor （MBBR） was used to treat real coal gasification wastewater. Nitrification of the MBBR was inhibited almost completely during start-up period. Sudden increase of influent total NH 3 concentration was the main factor inducing nitrification inhibition. Increasing DO concentration in the bulk liquid （from 2 to 3 mg/L） had little effect on nitrification recovery. Nitrification of the MBBR recovered partially by the addition of nitrifying sludge into the reactor and almost ceased within 5 days. Nitrification ratio of the MBBR achieved 65% within 12 days by increasing dilute ratio of the influent wastewater with tap water. The ratio of nitrification decreased to 25% when influent COD concentration increased from 650 to 1000 mg/L after nitrification recovery and recovered 70% for another 4 days.

Effect of alkalinity on nitrite accumulation in treatment of coal chemical industry wastewater using moving bed biofilm reactor

Nitrogen removal via nitrite （the nitrite pathway） is more suitable for carbon-limited industrial wastewater. Partial nitrification to nitrite is the primary step to achieve nitrogen removal via nitrite. The effect of alkalinity on nitrite accumulation in a continuous process was investigated by progressively increasing the alkalinity dosage ratio （amount of alkalinity to ammonia ratio, mol/mol）. There is a close relationship among alkalinity, pH and the state of matter present in aqueous solution. When alkalinity was insufficient （compared to the theoretical alkalinity amount）, ammonia removal efficiency increased first and then decreased at each alkalinity dosage ratio, with an abrupt removal efficiency peak. Generally, ammonia removal efficiency rose with increasing alkalinity dosage ratio. Ammonia removal efficiency reached to 88% from 23% when alkalinity addition was sufficient. Nitrite accumulation could be achieved by inhibiting nitrite oxidizing bacteria （NOB） by free ammonia （FA） in the early period and free nitrous acid in the later period of nitrification when alkalinity was not adequate. Only FA worked to inhibit the activity of NOB when alkalinity addition was sufficient.

The effect of bubble plume on oxygen transfer for moving bed biofilm reactor

The movement of the bubble plume plays an important role in the operation of a moving bed biofilm reactor （MBBR）, and it directly affects the contact and the mixture of the gas-liquid-solid phases in the aeration tank and also the oxygen transfer from the gas phase to the liquid phase. In this study, the velocity field is determined by a 4-frame PTV as well as the time-averaged and timedependent velocity distributions. The velocity distribution of the bubble plume is analyzed to evaluate the operating efficiency of the MBBR. The results show that the aeration rate is one of the main factors that sway the velocity distribution of the bubble plumes and affect the operating efficiency of the reactor.

Effects of carrier-attached biofilm on oxygen transfer efficiency in a moving bed biofilm reactor

Three laboratory-scale moving bed biofilm reactors （MBBR） with different carrier filling ratios ranging from 40% to 60% were used to study the effects of carrier-attached biofilm on oxygen transfer efficiency. In this study, we evaluated the performance of three MBBRs in degrading chemical oxygen demand and ammonia. The three reactors removed more than 95% of NH4^＋ -N at an air flow-rate of 60L·h^-1. The standard oxygen transfer efficiency （αSOTE） of the three reactors was also investigated at air flow-rates ranging from 60 to 100L·h^-1. These results were compared to αSOTE of wastewater with a clean carrier （no biofilm attached）. Results showed that under. these process conditions, αSOTE decreased by approximately 70% as compared to αSOTE of wastewater at a different carrier-filling ratio. This indicated that the biofilm attached to the cartier had a negative effect on αSOTE. Mechanism analysis showed that the main inhibiting effects were related to biofilm flocculants and soluble microbial product （SMP）. Biofilm flocs could decrease otSOTE by about 20%, and SMP could decrease aαSOTE by 30%--50%.

Fate of Parent and Substituted Polycyclic Aromatic Hydrocarbons in SBR/MBBR Treatment Process:Experimental Value Against Model Prediction

The knowledge of the existence,distribution and fate of polycyclic aromatic hydrocarbons(PAHs)and substituted polycyclic aromatic hydrocarbons(SPAHs)in wastewater treatment plants(WWTPs)was vital for reducing their concentrations entering the aquatic environment.The concentrations of 13 SPAHs and 16 PAHs were all determined in a WWTP with styrene butadiene rubber(SBR)in partnership with the moving bed biofilm reactor(MBBR)process.SPAHs presented a higher concentration lever than PAHs in nearly all samples.The total removal efficiencies of PAHs and SPAHs ranged from 64.0%to 71.36%and 78.4%to 79.7%,respectively.The total yearly loads of PAHs(43.0 kg)and SPAHs(73.0 kg)were mainly reduced by the primary and SBR/MBBR biological treatment stages.The tertiary treatment stage had a minor contribution to target compounds removal.According to a synthesis and improvement fate model,we found that the dominant processes changed as the chemical octanol water partition coefficient(K_(ow))increased.But the seasonal variations of experimental removal efficiencies were more obvious than that of predicted data.In the primary sedimentation tank,dissolution in the aqueous phase and sorption to sludge/particulate matter were controlling processes for the removal of PAHs and SPAHs.The sorption to sludge and biodegradation were the principal removal mechanisms during the SBR/MBBR biological treatment process.The contribution of volatilization to removal was always insignificant.Furthermore,the basic physicochemical properties and operating parameters influenced the fate of PAHs and SPAHs in the WWTP.