Effect of co‐contaminant phenol on performance of a laboratory‐scale RBC with algal‐bacterial biofilm treating petroleum hydrocarbon‐rich wastewater

BACKGROUND: Hydrocarbon degradation by algal‐bacterial systems has advantages over degradation by conventional heterotrophic systems. However, oily wastewaters often contain co‐contaminants that may inhibit the degradation of total petroleum hydrocarbons (TPH), leading to system failure. RESULTS: This paper reports the effect of phenol on treatment of wastewater containing petroleum hydrocarbons, i.e. diesel oil in a lab‐scale rotating biological contactor with biofilm consisting predominantly of Burkholderia cepacia and a freshwater algal culture. The effect of phenol loading from 0.11–0.69 g phenol m^?2 d^?1 on diesel degradation was studied with 21 h hydraulic retention time and TPH loading of 27.33 g TPH m^?2 d^?1. With increase in phenol loading, complete removal of phenol was observed. However, TPH removal decreased from 99% to 94% and significant decrease in TCOD removal was observed possibly due to biomass growth in suspension. Presence of algal culture in the biofilm made it feasible to operate the RBC at a high organic loading. The benefits included better immobilization of the bacterial culture, release of oxygen and generation of alkalinity. Lowering in pH due to accumulation of acidic intermediates formed during oil biodegradation was not observed in this study. CONCLUSION: This system can be recommended for treatment of industrial wastewaters containing TPH and phenols, with proper handling of biosolids. Copyright © 2010 Society of Chemical Industry     

Double‐deck aerated biofilm membrane bioreactor with sludge control for municipal wastewater treatment

Alternative designs of an aerated moving‐bed biofilm reactor and a flat‐sheet membrane module for a biofilm membrane bioreactor process have been investigated to overcome a membrane clogging problem and to determine the performance of a new membrane module. Double‐deck aerated biofilm reactor with integrated designs of sludge hopper, thickener, and velocity‐zone concept for particle settlement was evaluated for the suspended solid control and removal. Hydrodynamics of bubbling, liquid, and solid particles were arranged in the bioreactor to obtain a particle settlement. New membrane modules used under low suspended solid environment having smaller membrane gaps were evaluated for filtration performance and clogging problems for long‐term operation. The average suspended solids concentration in the bioreactor effluent was 44.6 mg/L. Relaxation applied with the membrane module provided the most optimum result for fouling control, and no clogging problems in the modules were observed in the system after continuous operation of 3 weeks. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Simultaneous removal of nitrogen and phosphorus from swine wastewater in a sequencing batch biofilm reactor

In this study, the performance of a sequencing batch biofilm reactor (SBBR) for removal of nitrogen and phosphorus from swine wastewater was evaluated. The replacement rate of wastewater was set at 12.5%throughout the exper-iment. The anaerobic and aerobic times were 3 h and 7 h, respectively, and the dissolved oxygen concentration of the aerobic phase was about 3.95 mg·L?1. The SBBR process demonstrated good performance in treating swine wastewater. The percentage removal of total chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) was 98.2%, 95.7%, 95.6%, and 96.2%at effluent concentrations of COD 85.6 mg·L?1, NH4+-N 35.22 mg·L?1, TN 44.64 mg·L?1, and TP 1.13 mg·L?1, respectively. Simultaneous nitrification and denitrification phenomenon was observed. Further improvement in removal efficiency of NH4+-N and TN occurred at COD/TN ratio of 11:1, with effluent concentrations at NH4+-N 18.5 mg·L?1 and TN 34 mg·L?1, while no such improvement in COD and TP removal was found. Microbial electron microscopy analysis showed that the fil er surface was covered with a thick biofilm, forming an anaerobic–aerobic microenvironment and facilitating the removal of nitrogen, phosphorus and organic matters. A long-term experiment (15 weeks) showed that stable removal efficiency for N and P could be achieved in the SBBR system.     

复合式膜生物反应器废水处理技术研究进展

复合式膜生物反应器结合了传统膜生物反应器与接触氧化工艺的优点,能在维持稳定高效的有机物去除率前提下,有效减缓膜污染,减少剩余污泥的排放,并为同步脱氮过程提供良好环境,因此近几年逐渐成为研究热点。文章综述了其构成、工作原理、类型及在处理不同废水中的应用,并展望了今后研究的努力方向。     

Investigation of biofilm growth and attrition in a three‐phase airlift bioreactor using 35SO42− as a radiolabelled tracer

The growth and biomass loss pattern for immobilized cells growing on diatomaceous earth particles in a three‐phase airlift bioreactor (TPALB) is studied using ³⁵S as a radiolabelled tracer. A monoculture of Beneckea natriegens was grown immobilized on support particles in a 3 L TPALB. Sterile conditions were maintained during the experiments, and n‐propanol was used as the sole carbon source. After the system reached steady state, the unlabelled sulfate (SO₄^2?) in the feed tank was substituted by a radioactive grade (³⁵SO₄^2?), and the assimilation of ³⁵S in the immobilized and in the suspended cells was monitored. The results indicated that the growth rate of immobilized biomass was not uniform throughout the biofilm. More specifically, it was concluded that cells growing closer to the external biofilm layer exhibit a higher growth rate, and that biomass loss from the biofilm was through attrition at the outer biofilm surface rather than by sloughing off of whole sections of biofilm. Copyright © 2006 Society of Chemical Industry     

Phenolic wastewater treatment in a three‐phase fluidised bed bioreactor containing low density particles

The treatment of phenolic wastewater was investigated in a gas–liquid–solid fluidised bed bioreactor containing polypropylene particles of density 910 kg m^?3. Measurements of chemical oxygen demand (COD) versus residence time (t) were performed for various ratios of settled bed volume to bioreactor volume (V_b/V_R) and air velocities (u) to determine the values of (V_b/V_R) and u for which the largest reduction in COD occurred. Optimal operation, corresponding to the largest COD removal, was attained when the bioreactor was controlled at the ratio (V_b/V_R) = 0.55 and an air velocity u = 0.036 m s^?1. Under these conditions, the value of COD was practically at steady state for times greater than 50 h. At this steady state, only about 50% COD removal was achieved in the treatment of a ‘raw’ wastewater (no mineral salts added), whereas in the operation with wastewater enriched in nutrient salts approximately 90% COD removal was attained. The following amount of mineral salts (mg dm^?3): (NH₄)₂SO₄—500; KH₂PO₄—200; MgCl₂—30; NaCl—30; CaCl₂—20; and FeCl₃—7, when added to wastewater before treatment, was sufficient for biomass growth. The application of low density particles (used as biomass support) in a bioreactor allowed the control of biomass loading in the apparatus. In the cultures conducted after change in (V_b/V_R) at a set u, the steady state mass of cells grown on the particles was achieved after approximately 6 days of operation. With change in u at a set (V_b/V_R), the new steady state biomass loading occurred after culturing for about 2 days. Phenolic wastewater was successfully treated in a bioreactor. In the operation conducted in a bioreactor optimally controlled at (V_b/V_R) = 0.55, u = 0.036 m s^?1 and t = 50 h, conversions greater than 99% were achieved for all phenolic constituents of the wastewater. Conversions of about 90% were attained for other hydrocarbons. Copyright © 2005 Society of Chemical Industry     

Process intensification in wastewater treatment: ferrous iron removal by a sustainable membrane bioreactor system

Biooxidation of ferrous iron (Fe²⁺) from strongly acidic industrial wastewater with a high Fe²⁺ content by Thiobacillus ferrooxidans in a packed bed reactor and subsequent removal of ferric iron (Fe³⁺) by a crossflow microfiltration (membrane) process have been investigated as functions of wastewater flowrate (54–672 cm³ h^?1), Fe²⁺ concentration (1.01–8.06 g dm^?3), and pH (1.5–5.0). A natural (vegetable) sponge, Luffa cylindrica, was used as support matrix material. The fastest kinetic performance achieved was about 40 g Fe²⁺ dm^?3 h^?1 at a true dilution rate of 19 h^?1 corresponding to a hydraulic retention time of 3.16 min. Steady state conversion was observed to be about 10% higher at pH 2.3 than that at pH 1.5. Increasing the flowrate of the inlet wastewater caused a reduction in conversion rate. The oxidation rate reduced along the reactor height as the wastewater moved towards the exit at the top but conversion showed the opposite trend. Increasing Fe²⁺ concentration up to a critical point resulted in an increased oxidation rate but beyond the critical point caused the oxidation rate to decrease. Luffa cylindrica displayed suitable characteristics for use as a support matrix for formation of a Thiobacillus ferrooxidans biofilm and showed promising potential as an ecological and sustainable alternative to existing synthetic support materials. Membrane separation was shown to be a very effective means of Fe³⁺ removal from the wastewater with removal changing from 92% at pH 2.3 to complete removal at pH 5.0. Copyright © 2003 Society of Chemical Industry     

厌氧膜生物反应器在废水处理中的研究进展

厌氧膜生物反应器是一种处理高浓度有机废水的有效工艺.综述了厌氧膜生物反应器的特征,在工业废水处理中的应用以及低温下厌氧处理低浓度废水的效果,并展望了厌氧膜生物反应器的应用前景.     

Phenol degradation in a fixed‐bed bioreactor using micro‐cellular polymer‐immobilized Pseudomonas syringae

Highly porous (85% void volume) polymer beads with interconnecting micro‐pores were prepared for the immobilization of Pseudomonas syringae for the degradation of phenol in a fixed‐bed column bioreactor. The internal architecture of this support material (also known as PolyHIPE Polymer) could be controlled through processing before the polymerization stage. The transient and steady state phenol utilization rates were measured as a function of substrate solution flow rate and initial substrate concentration. The spatial concentration of the bacteria on the micro‐porous support particles as well as within them was studied using scanning electron microscopy at various time intervals during the continuous operation of the bioreactor. It was found that although bacterial penetration into the porous support was present after 20 days, bacterial viability however, was compromised after 120 days as a result of the formation of a biofilm on the support particles. The steady state phenol utilization at an initial phenol concentration of 200 mg cm^?3 was 100% provided that the flow rate was less than 7 cm³ min^?1. Substrate inhibition at a constant flow rate of 4.5 cm³ min^?1 was found to begin at 720 mg dm^?3. The critical dilution rate for bacteria washout was high as a result of the highly hydrophobic nature of the support and the reduction of pore interconnect size due to bacterial growth within the pores in the vicinity of the surface of the support. Copyright © 2004 Society of Chemical Industry     

Pilot‐scale anaerobic/anoxic/oxic/oxic biofilm process treating coking wastewater

BACKGROUND: Biological treatment efficiency of coking wastewater is rather poor, especially for chemical oxygen demand (COD) and ammonia‐nitrogen (NH$_{4}^{+}$ ‐N) removal due to its complex composition and high toxicity. RESULTS: A pilot‐scale anaerobic/anoxic/oxic/oxic (A²/O²) biofilm system has been developed to treat coking wastewater, focusing attention on the COD and NH$_{4}^{+}$ ‐N removal efficiencies. Operational results over 239 days showed that hydraulic retention time (HRT) of the system had a great impact on simultaneous removals of COD and NH$_{4}^{+}$ ‐N. At HRT of 116 h, total removal efficiencies of COD and NH$_{4}^{+}$ ‐N were 92.3% and 97.8%, respectively, reaching the First Grade discharge standard for coking wastewater in China. Adequate HRT, anoxic removal of refractory organics and two‐step aerobic bioreactors were considered to be effective measures to obtain satisfactory coking effluent quality using the A²/O² biofilm system. The correlation between removal characteristics of pollutants and spatial distributions of biomass along the height of upflow bioreactors was also revealed. CONCLUSION: The study suggests that it is feasible to apply the A²/O² biofilm process for coking wastewater treatment, achieving desirable effluent quality and steady process performance. © 2012 Society of Chemical Industry     

Sustained nitrite accumulation in a membrane‐assisted bioreactor (MBR) for the treatment of ammonium‐rich wastewater

A membrane‐assisted bioreactor (MBR) for sustained nitrite accumulation is presented, treating a synthetic wastewater with total ammonium nitrogen (TAN) concentrations of 1 kg N m^?3 at a hydraulic retention time down to 1 day. Complete biomass retention was obtained by microfiltration with submerged hollow fibre membranes. A membrane flux up to 189.5 dm³ day^?1 m^?2 could be maintained at a suction pressure below 100 kPa. Nitrification was effectively blocked at the nitrite stage (nitritation), and nitrate concentration was less than 29 g N m^?3. The rate of aeration was reduced to obtain a mixture of ammonium and nitrite, and after adjusting this rate the TAN/NO₂‐N ratio in the reactor effluent was kept around unity, making it suitable for further treatment by anaerobic oxidation of ammonium with nitrite. After increasing again the rate of aeration, complete nitrification to nitrate recovered after 11 days. It is suggested that nitrite accumulation resulted from a combination of factors. First, the dissolved oxygen (DO) concentration in the reactor was always limited with concentrations below 0.1 g DO m^?3, thereby limiting nitrification and preventing significant nitrate formation. The latter is attributed to the fact that ammonium‐oxidising bacteria cope better with low DO concentrations than nitrite oxidisers. Second, the MBR was operated at a high ammonia concentration of 7–54 g N m^?3, resulting in ammonia inhibition of the nitrite‐oxidising microorganisms. Third, a temperature of 35 °C was reported to yield a higher maximum growth rate for ammonium‐oxidising bacteria than for nitrite‐oxidising bacteria. Nitrite oxidisers were always present in the MBR but were out‐competed under the indicated process conditions, which is reflected in low concentrations of nitrate. Oxygen limitation was shown to be the most important factor to sustain nitrite accumulation. Nevertheless, nitritation was possible at ambient temperature (22–24 °C), lower ammonia concentration (<7 g N m^?3) and when using raw nitrogenous wastewater containing some biodegradable carbon. Overall, application of the MBR for nitritation was shown to be a reliable technology. © 2003 Society of Chemical Industry     

Simultaneous removal of sulfate and selenate from wastewater by process integration of an ion exchange column and upflow anaerobic sludge blanket bioreactor

The application of an integrated process configuration comprising of an ion exchange (IX) column and an upflow anaerobic sludge blanket (UASB) bioreactor for the simultaneous removal of SO₄^2- and total Se from synthetic mine wastewater was evaluated. Use of an IX column as a pre-treatment (not as post-treatment) to the UASB bioreactor gave the best overall removal performance. The combined treatment reduced the total Se and SO₄^2- concentration from 8.0 and 1441 mg/L to 0.2 and 28.0 mg/L, respectively. This study demonstrated for the first time that an IX process as a pre-treatment to a biological process can significantly improve the oxyanion removal efficiency and the overall treatment of Se-laden wastewaters.     

Dyeing and printing wastewater treatment using a membrane bioreactor with a gravity drain

A laboratory-scale membrane bioreactor (MBR) with a gravity drain was tested for dyeing and printing wastewater treatment from a wool mill. The MBR was operated with continuous permeate by gravity and without chemical cleaning for 135 days. Results showed that excellent effluent quality could meet the reuse water standard in China. The average concentrations of COD, BOD₅, turbidity and color in the effluent were 36.9 mg l⁻¹, 3.7 mg l⁻¹, 0.2 NTU and 21 dilution times (DT), respectively. The average removal rates of COD, BOD₅, turbidity and color were 80.3%, 95.0%, 99.3% and 58.7%, respectively. The membrane flux increased with increasing of aeration intensity, and its increasing rate was related to pressure-heads. The higher the pressure-head, the greater the impact of aeration intensity on membrane flux. Statistical analysis also showed that both the pressure-head and aeration intensity significantly affected membrane flux. Due to its compact design, simple operation and easy maintenance, MBR with a gravitational filtration system hs low energy consumption and is cost-effective to build and operate. If the life expectancy of the membrane is set for 3–4 years and the membrane flux is set at 15 l/m²·h, such a MBR would be very competitive.