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关键词： Microalgae   Chlorella sp   Heavy metals   Biosorption kinetics   Tannery effluent   CO2 sequestration  

摘要： Recently, mass production of lipid along with heavy metal reduction is gaining momentum due to their cost-effective and greener approach towards waste water treatment. The purpose of this study is to investigate the small scale photo bioreactor treatment of tannery effluent using Chlorella sp. isolated form Yercaud lake, Tamil Nadu, India. The results showed a significant decrease in the heavy metals content in the tannery effluent after the treatment. Maximum reduction of the heavy metal Chromium (Cr) of 10.92 mg L-1 was recorded, followed by Cobalt (Co)-7.37 mg L-1, Nickel (Ni)-9.15 mg L-1, Cadmium (Cd)-8.48 mg L-1, Lead (Pb)-12.54 mg L-1, Zinc (Zn)-11.56 mg L-1 and Copper (Cu)-10.71 mg L-1 at the end of the 20th day of treatment. The microalgae, Chlorella sp. was analyzed for their biosorption ability and the maximum biosorption capacity (qmax) rate against heavy metals was 81.36, 70.53, 82.15, 63.29, 58.92, 83.43, 64.83 mu g L-1 for Cr, Pb, Ni, Cd, Co, Zn, and Cu respectively. It matched with the Langmuir and Freundlich kinetics models. The maximum CO2 utilization was found to be 60.50% and maximum concentration of lipid, carbohydrate and protein was found to be 0.95 g L-1, 250 mu g mL(-1) and 160 mu g mL(-1), respectively. The presence of various groups such as hydroxyl, alkyl, carbonyl and carboxylic acids was confirmed using Fourier transform infrared analysis. Thus, the isolated microalgae showed good biosorption ability towards the various heavy metal pollutants from tannery waste water.

关键词： Advanced oxidation processes   Anaerobic membrane bioreactor   Tertiary wastewater treatment   Contaminants of emerging concern   Pharmaceutical compound degradation  

摘要： Effluent from anaerobic membrane bioreactor (AnMBR) contains ammonia and would require post-polishing treatment before it can be disinfected by chlorine. However, additional post-treatment steps to remove nutrients offset the energetic benefits derived from anaerobic fermentation. The use of chlorine or ozone also promotes concerns associated with disinfection byproducts. This study evaluates UV/H2O2 as a potential strategy suited for the removal of pharmaceutical compounds as well as antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) from AnMBR effluent. Our findings indicate that 10 mg/L H2O2 and 61.5 mJ/cm2 of UV fluence are able to achieve a 4-log removal of both Escherichia coli PI7 and Klebsiella pneumoniae L7. However, a higher fluence of 311 mJ/cm2 with the same amount of H2O2 would be required to achieve >90% removal of atenolol, carbamazepine and estrone. The removal of the pharmaceutical compounds was driven by the hydroxyl radicals generated from H2O2, while UV exposure governed the inactivation of ARB and ARGs. UV/H2O2 increased overall mutagenicity of the treated wastewater matrix but did not result in any changes to the natural transformation rates. Instead, UV significantly reduced natural transformation rates by means of DNA damage. Overall, UV/H2O2 could be the ideal final disinfection strategy for AnMBR effluent without requiring additional post-treatment prior disinfection.

关键词： Bacterial immobilized reactor   Denitrification   Manganese-oxidizing bacteria   Microbial community structure   Tetracycline removal  

摘要： The co-existence of nitrate, manganese (Mn), and antibiotics are of a wide concern. In this study, a denitrifying and manganese-oxidizing Zoogloea Q7 bacterium was immobilized using polyvinyl alcohol/sodium alginate with sponge cube (PVA/SA@sponge cube) in the reactor. The optimal operation parameters of the bioreactor were explored. Maximum nitrate, Mn(II), and tetracycline (TC) removal efficiencies of 93.00, 72.34, and 57.32% were achieved with HRT of 10 h, pH of 6.5, Mn(II) concentration of 20 mg L-1, and TC of 1 mg L-1, respectively. Fluorescence excitation-emission matrix (EEM) proved that the microorganism in the bioreactor was greatly active. Scanning electron microscope (SEM) images demonstrated that Zoogloea Q7 was commendably immobilized on the novel material. X-ray diffraction (XRD) analysis suggested that the bioprecipitate was mainly composed of MnO2 and MnCO3. Through high-throughput analysis, Zoogloea sp. Q7 was considered to be the dominant bacteria present in the bioreactor.

关键词： municipal solid waste   landfill   leachate treatment   coupled model   numerical simulation  

摘要： Surface spraying, horizontal trenches, and vertical wells are the most common leachate recirculation system used at landfills in engineering practice. In order to quantify the efficiency of the three aforementioned recirculation systems, a hydro-biochem-mechanical-coupled model was developed in the present work, which can describe hydrodynamic and biochemical behaviors in food-waste-rich landfills. A typical landfill cell was modeled in COMSOL. The results indicate that leachate recirculation can accelerate the decomposition of municipal solid waste (MSW) with food-rich waste content, relieving acidification, improving gas generation efficiency, and consequently, increasing the early settlement in landfills.

关键词： Nitrogen removal (BNR) online monitoring   pH and ORP sensors   NH4+-N and NO3--N sensors   pH and ORP inflection point   Ammonia valley   Nitrate knee   ORP and pH first derivative  

摘要： Online sensors, which monitor the ammonia oxidation and the dissimilatory nitrate reduction process, can optimize aerobic and anoxic phase duration. The purpose of this study was to comparatively evaluate the effectiveness of online sensors that were in situ-located in an intermittently aerated and fed membrane bioreactor (IAF-MBR) system. Ammonium and nitrate nitrogen sensors equipped with ion-selective electrodes as well as pH and oxidation-reduction potential (ORP) sensors were employed to online monitoring and optimizing of ammonia oxidation and nitrate reduction processes. The "ammonia valley" or pH bending point, which is indicative of ammonia depletion, was effectively and repeatedly detected by measuring the pH profile, while the "nitrate knee" point, which indicates the completion of the denitrification process, was online-detected by obtaining the ORP profile. The "ammonia valley" and "nitrate knee" were detected at pH and ORP values of 6.47 +/- 0.02 and - 162 +/- 39 mV, respectively. The ORP and pH first derivatives (dORP/dt and dpH/dt) were found to be more suitable than the untransformed ORP and pH values in detecting pH and ORP inflection points and controlling the shift from the anoxic to the aeration phase. Specifically, the ORP and pH bending points were detected at dORP/dt and dpH/dt values of 1.64 +/- 0.82 mV min(-1)and 0.005 +/- 0.001 min(-1), respectively. Moreover, the ORP first derivative has appeared earlier than the ORP bending point.

关键词： Electrocoagulation   Phosphorus removal   Prolonged solids retention time   Wastewater treatment   Membrane fouling  

摘要： This study evaluated the effects of the electrocoagulation on membrane fouling and treatment performance in a membrane bioreactor operated with prolonged solids retention time. The membrane bioreactor was fed with synthetic wastewater, and its operation was conducted at three different experimental runs. Initially, the reactor was operated without electric current application (run 1), named as control period, and subsequently using electric current density of 5 A m(-2)(run 2) and 15 A m(-2)(run 3). Hence, the reactor performance was evaluated for the impact of electrocoagulation on fouling mitigation and pollutant removal (chemical oxygen demand, phosphorus and ammonium) as well as for the use of two different current densities. The results showed that the use of the lower current density (run 2) was able to significantly improve the membrane bioreactor performance on organic matter and phosphorus removal, showing average efficiencies of 95 and 99%, respectively. Particularly for ammonium removal, the membrane bioreactor exhibited a gradual increase from run 1 to 3, attaining the highest ammonium removal efficiency (86%) during run 3. Compared to run 1 and 3, the use of 5 A m(-2)resulted in a better mixed liquor filterability conditions and consequently in a lower membrane fouling rate (0.107 bar d(-1)). Therefore, the integration of electrocoagulation with the membrane bioreactor technology proved to be an interesting alternative to improve the treatment performance and attenuate the fouling process, even operating the reactor without sludge discharge.

关键词： Anaerobic dynamic membrane   Reactor configuration   Microbial community distribution   Membrane fouling  

摘要： Recently, anaerobic self-forming dynamic membrane bioreactors (AnSFDMBRs) have attracted increasing attention, and are considered as an alternative to conventional anaerobic membrane bioreactors (AnMBRs). The key advantages of AnSFDMBRs include high flux, low propensity towards fouling, and low capital and operational costs. Although there have been several reviews on AnMBRs, very few reviews on AnSFDMBR system. Previous AnSFDMBR studies have focused on lab-scale to investigate the long-term flux, methods to improve performance and the associated mechanisms. Microbial analysis showed that the phyla namely Proteobacteria, Bacteroidetes and Firmicutes are dominant in both bulk sludge and cake biofilm, but their abundance is low in biocake. This review critically examines the fundamentals of AnSFDMBRs, operational conditions, process optimization and applications. Moreover, the current knowledge gaps (e.g., dynamic membrane module optimization, membrane surface modification and functional microbes enrichment) that should be studied in future to design an efficient AnSFDMBR system for treatment of diverse wastewaters.

关键词： Planetary Centrifugal Bioreactor   CFD   Oxygen Transfer   Mixing   Shear Stress  

摘要： Planetary centrifugal bioreactors are promising candidates for cell culture platforms since there is no pollution caused by stirring blades. In this work, the fluid structure in a planetary centrifugal bioreactor was investigated using the computational fluid dynamics (CFD) method. The effects of operating conditions on the oxygen transfer rate (OTR), mixing efficiency and shear environment of the bioreactor were studied with the revolution speed (N) ranging from 60 to 160 rpm and the rotation-to-revolution speed ratio (i) from -2 to 1. The results show that the volumetric mass transfer coefficient (k(L)a), turbulence intensity, volumetric power consumption, and shear stress increase along with the increase of the revolution and rotation speeds. Furthermore, the rotation in the opposite direction to the revolution is beneficial to the performance of the bioreactor. The planetary centrifugal bioreactor has a higher k(L)a of 50-200/h and a lower average shear stress of 0.01-0.05 Pa in comparison with conventional stirred tank bioreactors, which makes it suitable for biological culture of oxygen-consuming cells and shear-sensitive cells.

关键词： thermophilic   wastewater   surfactants   denitrification   sludge production   biological activity   nitrogen uptake rate  

摘要： To date, the management of high-strength wastewater represents a serious problem. This work aims to evaluate the performance on chemical pollutants and on sludge production of one of the two full-scale thermophilic membrane bioreactors (ThMBRs) currently operational in Italy, based on monitoring data of the last two and a half years. Removal yields on COD, N-NOx, non-ionic and anionic surfactants (TAS and MBAS), increased with the input load up to 81.9%, 97.6%, 94.7%, and 98.4%, respectively. In the period of stability, a very low value of sludge production (0.052 kg(VS) kgCOD(-1)) was observed. Oxygen uptake rate (OUR) tests allowed us to exclude the possibility that mesophilic biomass generally exhibited any acute inhibition following contact with the aqueous residues (ARs), except for substrates that presented high concentrations of perfluoro alkyl substances (PFAS), cyanides and chlorides. In one case, nitrifying activity was partially inhibited by high chlorides and PFAS concentration, while in another the substrate determined a positive effect, stimulating the phenomenon of nitrification. Nitrogen uptake rate (NUR) tests highlighted the feasibility of reusing the organic carbon contained in the substrate as a source in denitrification, obtaining a value comparable with that obtained using the reference solution with methanol. Therefore, respirometric tests proved to be a valid tool to assess the acute effect of AR of ThMBR on the activity of mesophilic biomass in the case of recirculation.

关键词： Sucrose concentration   Inoculation density   Aeration rate   Kinetic study   Antioxidant activity  

摘要： Eurycoma longifolia is a precious medicinal plant that currently faces resource shortage. The Dbioreactor culture of adventitious roots (ARs) can be an efficient route for the rapid and large-scale production of the useful metabolites of this plant species. Eurycomanone and polysaccharides are the important bioactive compounds of E. longifolia;however, the bioreactor AR culture targeting the production of both compounds has not been explored. In this work, E. longifolia ARs were cultured in bubble column bioreactors and the bioreactor culture conditions to produce eurycomanone and polysaccharides were optimized by controlling sucrose concentration, inoculation density, and aeration rate. Kinetic study was subsequently implemented to confirm the culture period. The antioxidant activity of ARs were determined to provide a reference for the further production of related products. Results showed that E. longifolia ARs well grew in the bioreactor, and 40 g/L sucrose, 5 g/L inoculation density, and 0.05 vvm aeration rate were the optimal conditions for the production of ARs containing the highest eurycomanone and polysaccharide yields. Kinetic study revealed that 40 days of culture was the most suitable culture period, that produced 8.8 mg/L eurycomanone and 2.4 g/L polysaccharides. The ARs efficiently scavenged DPPH and ABTS radicals and possessed Fe2+ chelating ability, thereby indicating their potential use in the production of antioxidant related products.