Fluidized-Bed Bioreactor Applications for Biological Wastewater Treatment： A Review of Research and Developments

Wastewater treatment is a process that is vital to protecting both the environment and human health. At present, the most cost-effective way of treating wastewater is with biological treatment processes such as the activated sludge process, despite their long operating times. However, population increases have created a demand for more efficient means of wastewater treatment, Fluidization has been demonstrated to in- crease the efficiency of many processes in chemical and biochemical engineering, but it has not been widely used in large-scale wastewater treatment. At the University of Western Ontario, the circulating fluidized-bed bioreactor （CFBBR） was developed for treating wastewater. In this process, carrier particles develop a biofilm composed of bacteria and other microbes. The excellent mixing and mass transfer characteristics inherent to fluidization make this process very effective at treating both municipal and industrial wastewater. Studies of lab- and pilot-scale systems showed that the CFBBR can remove over 90% of the influent organic matter and 80% of the nitrogen, and produces less than one-third as much biological sludge as the activated sludge process. Due to its high efficiency, the CFBBR can also be used to treat wastewaters with high organic solid concentrations, which are more difficult to treat with conventional methods because they require longer residence times; the CFBBR can also be used to reduce the system size and footprint. In addition, it is much better at handling and recovering from dynamic loadings （i.e., varying influent volume and concentrations） than current systems. Overall, the CFBBR has been shown to be a very effective means of treating wastewa- ter, and to be capable of treating larger volumes of wastewater using a smaller reactor volume and a shorter residence time. In addition, its compact design holds potential for more geographically localized and isolat- ed wastewater treatment systems.

Evaluation of the Inverse Fluidized Bed Biological Reactor for Treating High-Strength Industrial Wastewaters

The aim of this work was to investigate the aerobic degradation of high-strength industrial (refinery) wastewaters in the inverse fluidized bed biological reactor, in which polypropylene particles of density 910 kg/m3 were fluidized by an upward flow of gas through a bed. Measurements of chemical oxygen demand (COD) versus residence time t were performed for various ratios of settled bed volume to reactor volume (Vb/VR) and air velocities u. The largest COD reduction, namely, from 54,840 to 2,190 mg/l, i.e. a 96% COD decrease, was achieved when the reactor was operated at the ratio (Vb/VR) = 0.55, air velocity u = 0.046 m/s and t = 65 h. Thus, these values of (Vb/VR), u and t can be considered as the optimal operating parameters for a reactor when used in treatment of high-strength refinery wastewaters. In the treatment operation conducted in a reactor optimally controlled at (Vb/VR) = 0.55, u = 0.046 m/s and t = 65 h, the conversions obtained for all phenolic constituents of the wastewater were larger than 95%. The conversions of about 90% were attained for other hydrocarbons.

Purification and reclamation of wastewater by an integrated biological pond system

The feasibility of an inexpensive wastewater treatment system is evaluated in this study.The experiment was conducted in 3 phases with different treatment combinations for testing theirpurification efficiencies. The pond system was divided into 3 functional regions: influentpurification, efficient upgrading and multi-utilization. Various kinds of aquatic organisms, wereeffectively cooperated in this system. The system attained high reduction of BOD_5, COD, TSS, TN,TP and other pollutants. The mutagenic effect and number of bacteria and virus significantly de-clined during the process of purifieation. After the wastewater flowed through the upgrading zone,the concentrations of pollutants and algae evidently decreased. Plant harvesting did not yield drama-tic effects on reductions of the main pollutants, through it did affect remarkably the biomassproductivity of the macrophytes. The wastewater was reclaimed for various purposes.

Optimal Aerations in the Inverse Fluidized Bed Biofilm Reactor When Used in Treatment of Industrial Wastewaters of Various Strength

The aim of this work was the determination of the optimal aerations, and more specifically the corresponding optimal air velocities uopt, at which the largest COD removals were achieved in treatment of industrial wastewaters of various strength conducted in the inverse fluidized bed biofilm reactor. The largest COD removals were achieved at the following air velocities uopt and retention times ts, and (Vb/VR) = 0.55: i) for CODo = 72,780 mg/l at uopt = 0.052 m/s and ts = 80 h;ii) for CODo = 62,070 mg/l at uopt = 0.042 m/s and ts = 65 h;iii) for CODo = 49,130 mg/l at uopt = 0.033 m/s and ts= 55 h;iv) for CODo = 41,170 mg/l at uopt = 0.028 m/s and ts = 45 h;v) for CODo = 35,460 mg/l at uopt = 0.025 m/s and ts = 27.5 h;and vi) for CODo = 26,470 mg/l at uopt= 0.014 m/s and ts = 22.5 h. In the treatment operation conducted in a reactor optimally controlled at the above values of uopt, ts and (Vb/VR), the following decreases in COD were obtained: i) from 72,780 to 5410 mg/l;ii) from 62,070 to 3730 mg/l;iii) from 49,130 to 2820 mg/l;iv) from 41,170 to 1820 mg/l;v) from 35,460 to 1600 mg/l;and vi) from 26,470 to 1180 mg/l, that is, approximately a 93%, 94%, 95%, 96%, 95% and 96% COD reduction was attained, respectively.

Optimization of Two-species Whole-cell Immobilization System Constructed with Marine-derived Fungi and Its Biological Degradation Ability

Mycelia pellet formed spontaneously in the process of cultivation was exploited as a biological carrier for whole-cell immobilization due to its unique structural characteristic. An innovative two-species whole-cell im- mobilization system was achieved by inoculating the marine-derived fungus Pestalotiopsis sp. J63 spores into cul- ture medium containing another fungus Penicillium janthinellum P1 pre-grown mycelia pellets for 2 days without any pretreatment. In order to evaluate the biological degradation capacity of this novel constructed immobilization system, the immobilized pellets were applied to treat paper mill effluent and decolorize dye Azure B. The use of the constructed immobilization system in the effluent resulted in successful and rapid biodegradation of numerous in- soluble fine fibers. The optimum conditions of immobilized procedure for maximum biodegradation capacity were determined using orthogonal design with biomass of P1 pellets 10 g （wet mass）, concentration of J63 spore 2x109 mlq, and immobilization time 2 d. The results demonstrate that immobilized pellets have more than 99% biodegradation capacity in a ten-hour treatment process. The kinetics of biodegradation fits the Michaelis-Menten equation well. Besides, the decolorization capability of immobilized pellets is more superior than that of P1 mycelia pellets. Overall, the present study offers a simple and reproducible way to construct a two-species whole-cell immobiliza- tion system for sewage treatment.

Factors affecting biological denitrifying dephosphatation in anaerobic/anoxic/aerobic sequencing batch reactor

This study was conducted to verify and discuss the denitrifying dephosphatation under different levels of nitrate concentration and retention time of anoxic/aerobic process in a Sequencing Batch Reactor (SBR). The results of tests demonstrated that there were two kinds of phosphorus-accumulating organisms (PAOs) in the biological excess phosphorus removal (BEPR) system. One was non-DNPAOs that could only use oxygen as terminal electron acceptors, the other was denitrifying PAOs (DNPAOs) that could use both nitrate and oxygen as terminal electron acceptors. Phosphorus uptake efficiency could be attained under anoxic period ranging from 28.7%-96.7% in an anaerobic/anoxic/aerobic system. Experimental results showed that nitrate concentration and retention time of anoxic/aerobic process were the key factors affecting the course of denitrifying dephosphatation.

Immobilized microalgal system:An achievable idea for upgrading current microalgal wastewater treatment

Efficient wastewater treatment accompanied by sustainable“nutrients/pollutants waste-wastewaterresources/energy nexus”management is acting as a prominent and urgent global issue since severe pollution has occurred increasingly.Diverting wastes from wastewater into the value-added microalgalbiomass stream is a promising goal using biological wastewater treatment technologies.This review proposed an idea of upgrading the current microalgal wastewater treatment by using immobilized microalgal system.Firstly,a systematic analysis of microalgal immobilization technology is displayed through an in-depth discussion on why using immobilized microalgae for wastewater treatment.Subsequently,the main technical approaches employed for microalgal immobilization and pollutant removal mechanisms by immobilized microalgae are summarized.Furthermore,from high-tech technologies to promote large-scale production and application potentials in diverse wastewater and bioreactors to downstream applications lead upgradation closer,the feasibility of upgrading existing microalgal wastewater treatment into immobilized microalgal systems is thoroughly discussed.Eventually,several research directions are proposed toward the future immobilized microalgal system for microalgal wastewater treatment upgrading.Together,it appears that using immobilization for further upgrading the microalgae-based wastewater treatment can be recognized as an achievable alternative to make microalgal wastewater treatment more realistic.The information and perspectives provided in this review also offer a feasible reference for upgrading conventional microalgae-based wastewater treatment.

treatment of swine wastewater in aerobic granular reactors： comparison of different seed granules as factors

The granulation process, physic-chemical properties, pollution removal ability and bacterial com- munities of aerobic granules with different feed-waste- water （synthetic wastewater, R1; swine wastewater, R2）, and the change trend of some parameters of two types of granules in long-term operated reactors treating swine wastewater were investigated in this experiment. The result indicated that aerobic granulation with the synthetic wastewater had a faster rate compared with swine waste- water and that full granulation in R 1 and R2 was reached on the 30th day and 39th day, respectively. However, although the feed wastewater also had an obvious effect on the biomass fraction and extracellular polymeric sub- stances of the aerobic granules during the granulation process, these properties remained at a similar level after long-term operation. Moreover, a similar increasing trend could also be observed in terms of the nitrogen removal efficiencies of the aerobic granules in both reactors, and the average specific removal rates of the organics and ammonia nitrogen at the steady-state stage were 35.33mg.g^-1 VSS and 51.46mg.g^-1 VSS for R1, and 35.47mg.g^-1 VSS and 51.72mg.g^-1 VSS for R2, respectively. In addition, a shift in the bacterial diversity occurred in the granulation process, whereas bacterial communities in the aerobic granular reactor were not affected by the seed granules after long-term operation.

Recent improvements in oily wastewater treatment:Progress, challenges, and future opportunities

Oily wastewater poses significant threats to the soil, water, air and human beings because of the hazardous nature of its oil contents. The objective of this review paper is to highlight the current and recently developed methods for oily wastewater treatment through which contaminants such as oil, fats, grease, and inorganics can be removed for safe applications.These include electrochemical treatment, membrane filtration, biological treatment,hybrid technologies, use of biosurfactants, treatment via vacuum ultraviolet radiation,and destabilization of emulsions through the use of zeolites and other natural minerals.This review encompasses innovative and novel approaches to oily wastewater treatment and provides scientific background for future work that will be aimed at reducing the adverse impact of the discharge of oily wastewater into the environment. The current challenges affecting the optimal performance of oily wastewater treatment methods and opportunities for future research development in this field are also discussed.

An innovative integrated system utilizing solar energy as power for the treatment of decentralized wastewater

This article reports an innovative integrated system utilizing solar energy as power for decentralized wastewater treatment, which consists of an oxidation ditch with double channels and a photovoltaic （PV） system without a storage battery. Because the system operates without a storage battery, which can reduce the cost of the PV system, the solar radiation intensity affects the amount of power output from the PV system. To ensure that the power output is sufficient in all different weather conditions, the solar radiation intensity of 78 W/m 2 with 95% confidence interval was defined as a threshold of power output for the PV system according to the monitoring results in this study, and a step power output mode was used to utilize the solar energy as well as possible. The oxidation ditch driven by the PV system without storage battery ran during the day and stopped at night. Therefore, anaerobic, anoxic and aerobic conditions could periodically appear in the oxidation ditch, which was favorable to nitrogen and phosphate removal from the wastewater. The experimental results showed that the system was efficient, achieving average removal efficiencies of 88% COD, 98% NH 4 ＋ -N, 70% TN and 83% TP, under the loading rates of 140 mg COD/（g MLSS·day）, 32 mg NH 4 ＋ -N/（g MLSS·day）, 44 mg TN/（g MLSS·day） and 5 mg TP/（g MLSS·day）.

Integrated energy view of wastewater treatment:A potential of electrochemical biodegradation

It has been more than one century since the activated sludge process was invented.Despite its proven stability and reliability,the energy(especially the electrical energy)use in wastewater treatment should evolve to meet the increasingly urgent demand of energy efficiency.This paper discusses how the energy utilized in conventional biological wastewater treatment can be altered by switching the indirect energy input to a direct electricity injection,which is achieved by the elecfrode integration providing extra thermodynamic driving force to biodegradation.By using electrodes instead of oxygen as terminal electron acceptors,the electrical energy can be utilized more efficiently,and the key of direct use of electrical energy in biodegradation is the development of highly active electroactive biofilm and the increase of electron transfer between microbes and the electrode.Furthermore,the synergy of different microbial electrochemical units has additional benefit in energy and resource recovery,making wastewater treatment more sustainable.

Simultaneous denitrification and denitrifying phosphorus removal in a full-scale anoxic–oxic process without internal recycle treating low strength wastewater

Performance of a full-scale anoxic-oxic activated sludge treatment plant（4.0×10-5 m-3/day for the first-stage project） was followed during a year.The plant performed well for the removal of carbon,nitrogen and phosphorus in the process of treating domestic wastewater within a temperature range of 10.8℃ to 30.5℃.Mass balance calculations indicated that COD utilization mainly occurred in the anoxic phase,accounting for 88.2% of total COD removal.Ammonia nitrogen removal occurred 13.71% in the anoxic zones and 78.77% in the aerobic zones.The contribution of anoxic zones to total nitrogen（TN） removal was 57.41%.Results indicated that nitrogen elimination in the oxic tanks was mainly contributed by simultaneous nitrification and denitrification（SND）.The reduction of phosphorus mainly took place in the oxic zones,51.45% of the total removal.Denitrifying phosphorus removal was achieved biologically by 11.29%.Practical experience proved that adaptability to gradually changing temperature of the microbial populations was important to maintain the plant overall stability.Sudden changes in temperature did not cause paralysis of the system just lower removal efficiency,which could be explained by functional redundancy of microorganisms that may compensate the adverse effects of temperature changes to a certain degree.Anoxic-oxic process without internal recycling has great potential to treat low strength wastewater（i.e.,TN 〈 35 mg/L） as well as reducing operation costs.

Effect of activated sludge treatment on the formation of N–nitrosamines under different chloramination conditions

Municipal wastewater discharge is considered as one of the main sources of N-nitrosamine precursors which can impact the qualities of downstream source waters and reclaimed wastewaters for potable reuse. N –Nitrosamine precursors can be removed to various degrees during biological wastewater treatment(e.g., the activated sludge(AS) process). So far, little is known about the impact of the AS process on N-nitrosamine formation under practical disinfection condition(e.g., uniform formation condition(UFC)). In this study, N-nitrosamine UFC from selected model compounds, sewage components(i.e., blackwaters and greywaters) and sewage samples were comprehensively investigated during batch AS treatment tests. N –Nitrosodimethylamine(NDMA) formation from the tested precursor compounds(i.e., trimethylamine(TMA) and sumatriptan(SMTR)) under UFC chloramination decreased mostly after 6 or 24 hr treatment with different types of AS(i.e., domestic rural AS, domestic urban AS, and textile AS), and the reductions in NDMA UFC were comparable to their NDMA formation potential(FP) reductions. In urine and feces blackwaters, NDMA UFC increased after 6 or 24 hr treatment with the domestic(i.e., rural and urban) AS, while NDMA FP decreased substantially. The increases in NDMA UFC after AS treatment was presumably attributed to the removal of bulk organic matters(e.g., dissolved organic carbon(DOC)) which favored NDMA formation under UFC. On the other hand, in laundry greywaters having relatively abundant DOC, N-nitrosamine UFC was less affected by DOC removal before or after AS treatment, but decreased to similar degrees with N-nitrosamine FP. In sewage samples collected from wastewater treatment plants, N-nitrosamines UFC tended to increase or remain constant during AS treatment, despite the decreases in their FPs. These results suggest that biological wastewater treatment(e.g., the AS process) may not effectively reduce N-nitrosamine formation(e.g., measured under UFC) partially because the concurrent removal of bulk organic matters(e.g., DOC) favored N-nitrosamine formation in s econdary effluents.

A full-scale integrated-bioreactor with two zones treating odours from sludge thickening tank and dewatering house： performance and microbial characteristics

A full-scale integrated-bioreactor consisting of a suspended zone and an immobilized zone was employed to treat the ordours emitted from a wastewater treatment plant. The inlet concentrations of H,S and NH3 were 1.6-38.6 mg.m-3 and 0.1 6.7 mg.m-3 respectively, while the steady-state outlet concentrations were reduced to 0-2.8mg.m - for H2S and 0-0.5mg.m for NH3. BothH2SandNH3 were eliminated effectively by the integrated-bioreactor. The removal efficiencies of H2S and NH3 differed between the two zones. Four species of microorganisms related to the degradation of H2S and NH3 were isolated. The characteristics and distributions of the microbes in the bioreactor depended on the inlet concentration of substrates and the micro-environmental conditions in the individual zones. Product analysis indicated that most of the H2S was oxidized into sulfate in the immobilized zone but was dissolved into the liquid phase in the suspended zone. A large amount of NH3 was converted into nitrate and nitrite by nitration in the suspended zone, whereas only a small amount of NH3 was transferred to the aqueous phase mainly by absorption or chemical neutralization in the immobilized zone. Different microbial populations dominated the individual zones, and the major biodegradation products varied accordingly.

Quantifying and managing regional greenhouse gas emissions: Waste sector of Daejeon, Korea

A credible accounting of national and regional inventories for the greenhouse gas （GHG） reduction has emerged as one of the most significant current discussions. This article assessed the regional GHG emissions by three categories of the waste sector in Daejeon Metropolitan City （DMC）, Korea, examined the potential for DMC to reduce GHG emission, and discussed the methodology modified from Intergovernmental Panel on Climate Change and Korea national guidelines. During the last five years, DMC＇s overall GHG emissions were 239 thousand tons C02 eq./year from eleven public environmental infrastructure facilities, with a population of 1.52 million. Of the three categories, solid waste treatment/disposal contributes 68%, whilst wastewater treatment and others contribute 22% and 10% respectively. Among GHG unit emissions per ton of waste treatment, the biggest contributor was waste incineration of 694 kg CO2 eq./ton, followed by waste disposal of 483 kg CO2 eq./ton, biological treatment of solid waste of 209 kg CO2 eq./ton, wastewater treatment of 0.241 kg CO2 eq./m3, and public water supplies of 0.067 kg CO2 eq./m3. Furthermore, it is suggested that the potential in reducing GHG emissions from landfill process can be as high as 47.5% by increasing landfill gas recovery up to 50%. Therefore, it is apparent that reduction strategies for the main contributors of GHG emissions should take precedence over minor contributors and lead to the best practice for managing GHGs abatement.