Anaerobic treatment of industrial wastewater using upflow anaerobic reactors is an extended trend due to its high efficiency and biogas production potential, but its implementation in some sectors is limited due to the complexity and toxicity of the wastewaters. In this study, a two-stage expanded granular sludge bed (EGSB) reactors system has been investigated at both bench and pilot scale for the treatment of complex and toxic real wastewater from a petrochemical industry. The effect of different operational parameters including organic loading rate (OLR), hydraulic retention time (HRT) and influent characteristics over COD removal and biogas production and composition have been studied. Additionally, biomass specific methanogenic activity (SMA) and wastewater toxicity have been evaluated after long-term operation. Optimum total HRT of 24 h has been determined resulting in total COD and SO4 2- removal of 56.30 ± 5.25% and 31.68 ± 14.71%, respectively, at pilot scale, and average biogas production of 93.47 ± 34.92 NL/day with 67.01 ± 10.23 %CH4 content and 5210.11 ± 6802.27 ppmv of H2S. SMA and toxicity tests have confirmed inhibitory and toxic effects of wastewater over anaerobic biomass with average maximum inhibition of 65.34% in the unacclimated anaerobic inoculum while chronic toxicity produced a decrease of an order of magnitude in SMA after 600 days of operation. This study demonstrates the feasibility of applying an anaerobic treatment to this wastewater using EGSB reactors between a 0.97-1.74 gCOD/L/day OLR range. Nonetheless, periodic reinoculation would be necessary for long-term operation due to chronic toxicity of the wastewater exerted on the anaerobic biomass. PRACTITIONER POINTS: A two-stage EGSB reactors system has been operated at bench and pilot scale to treat complex and toxic petrochemical wastewater. Optimal total HRT of 24 h resulted in average COD removal ranging from 40% to 60%. SMA and toxicity tests have been performed to study long-term acclimation, detecting an activity depletion of an order of magnitude.

Effective elimination of heavy metals from complex wastewater is of great significance for industrial wastewater treatment. Herein, bimetallic adsorbent Fe3O4-CeO2 was prepared, and H2O2 was added to enhance Sb(V) adsorption by Fe3O4-CeO2 in complex wastewater of Sb(V) and aniline aerofloat (AAF) for the first time. Fe3O4-CeO2 showed good adsorption performance and could be rapidly separated by external magnetic field. After five adsorption/desorption cycles, Fe3O4-CeO2 still maintained good stability. The maximum adsorption capacities of Fe3O4-CeO2 in single Sb(V), AAF + Sb(V), and H2O2+AAF + Sb(V) systems were 77.33, 70.14, and 80.59 mg/g, respectively. Coexisting AAF inhibited Sb(V) adsorption. Conversely, additional H2O2 promoted Sb(V) removal in AAF + Sb(V) binary system, and made the adsorption capacity of Fe3O4-CeO2 increase by 14.90%. H2O2 could not only accelerate the reaction rate, but also reduce the optimal amount of adsorbent from 2.0 g/L to 1.2 g/L. Meanwhile, coexisting anions had little effect on Sb(V) removal by Fe3O4-CeO2+H2O2 process. The adsorption behaviors of Sb(V) in three systems were better depicted by pseudo-second-order kinetics, implying that the chemisorption was dominant. The complexation of AAF with Sb(V) hindered the adsorption of Sb(V) by Fe3O4-CeO2. The complex Sb(V) was oxidized and decomposed into free state by hydroxyl radicals produced in Fe3O4-CeO2+H2O2 process. Then the free Sb(V) was adsorbed by Fe3O4-CeO2 mostly through outer-sphere complexation. This work provides a new tactic for the treatment of heavy metal-organics complex wastewater.

The electrochemical technologies for water treatment have flourished over the last decades. However, it is still challenging to treat the actual complex water effluents by a single electrochemical process, often requiring coupling of technologies. In this study, an upgraded peroxi-coagulation (PC) process with a magnetically assembled mZVI/DSA anode has been devised for the first time. COD, NH3-N and total phosphorous were simultaneously and effectively removed from livestock wastewater. The advantages, influence of key parameters and evolution of electrogenerated species were systematically investigated to fully understand this novel PC process. The fluorescent substances in livestock wastewater could also be almost removed under optimal conditions (300 mA, 0.2 g ZVI particles and pH 6.8). The interaction between OH and active chlorine yielded ClO with a high steady-state concentration of 6.85 × 10-13 M, which did not cause COD removal but accelerated the oxidation of NH3-N. The Mulliken population suggested that OH and NH3-N had similar electron-donor behavior, whereas ClO acted as an electron-withdrawing species. Besides, although the energy barrier for the reaction between OH and NH3-N (17.0 kcal/mol) was lower than that with ClO (18.8 kcal/mol), considering the tunneling in the H abstraction reaction, the Skodje-Truhlar method adopted for calculations evidenced a 17-fold faster NH3-N oxidation rate with ClO. In summary, this work describes an advantageous single electrochemical process for the effective treatment of a complex water matrix.

Different physicochemical properties between Cr(VI) and phenolic compounds pose serious challenges for the effective treatment of co-contamination. This study developed an electrodeless high-flow microwave atmospheric plasma jet for the single-step simultaneous degradation of p-nitrophenol (PNP) and reduction of Cr(VI). Following a 15 min treatment with microwave atmospheric pressure plasma, the removal efficiency of Cr(VI) and PNP reached 97.5% and 93.6%, respectively, whereas that of total organic carbon reached 30.2%. Adding PNP to the solution significantly improved Cr(VI) reduction, whereas PNP degradation increased slightly with Cr(VI). The results indicate that the PNP intermediates significantly affected Cr(VI) reduction. Additionally, long-lived H2O2 and short-lived ·H aided the reduction of Cr(VI) during plasma treatment. The addition of hydroxyl scavengers during treatment implied that ·OH was largely responsible for PNP oxidation. High-performance liquid chromatography-mass spectroscopy (HPLC-MS) revealed that PNP intermediates, including p-nitrocatechol and 5-nitrobenzene-1,2,3-triol, function as Cr(VI) reductants. On the basis of the examined intermediate products, the potential PNP degradation pathway was investigated. The factors that could influence simultaneous dehgradation and reduction, including solution pH, gas velocity, and distance between the plasma outlet and the water surface were researched. Low pH supports Cr(VI) reduction, and the promotion of PNP for Cr(VI) reduction applies to all pH values. The degradation of PNP is insensitive to pH values with or without Cr(VI). The optimal gas velocity for PNP degradation and Cr(VI) reduction was revealed to be 6 L/min. The simultaneous removal of PNP and Cr(VI) benefits from a shorter distance between the plasma outlet and the water\'s surface.

Dinitrosalicylic acid-functionalized chitosan, CHN-DNSA, was developed and improved the adsorption property against chromium Cr(VI) and/or Rhodamine B (RHB). Here, the disposal of wastewater bearing Cr(VI) and RHB from a complex system was ascribed to significant differences in physicochemical properties. The constructed CHN-DNSA surface charge is responsible for different interactions enabling simultaneous capture of pollutants. The excellent adsorption potency of Cr(VI) at pH 3.0 was 98.4% within a remarkable 1 h and the adsorption performance was 91.1% for RHB. The ionic strength was affected, reducing the removal % of Cr(VI) to 36.7% whereas 0.1 M NaCl meliorated the removal efficiency from 91.6 to 96.2% for RHB and from 82.3 to 89.1% for a binary system. Also, the exploited elimination process of Cr(VI) and/or RHB obeyed the 2nd model of kinetics and the Freundlich system. Good recovery, superior capacity, and synthetic approach make this protocol promising for wastewater treatment.

Herein, a novel Fe3+-stabilized magnetic polydopamine composite (Fe3O4/PDA-Fe3+) was facilely constructed, systematically characterized, and subsequently applied for the first time as a versatile adsorbent for treatment of Methylene blue (MB) in complex wastewater. Results showed that as-prepared material had prominent adsorption ability toward MB in its single dye solution over a wide pH range (3-10) with qmax value of 608.8 mg/g at 318 K. More interestingly, MB could be selectively captured by resulting adsorbent from mixed dye solutions (MB-cationic dye and MB-anionic dye) and complex aqueous solution with high ionic strength up to 0.5 mol/L NaCl. It was eventually revealed that the enhanced and selective adsorption of MB by as-resultant adsorbent was due to the synergistic effects between multiple uptake mechanisms. What\'s more, its adsorption efficiency toward MB in simulated wastewater still maintained higher than 80 % of its original uptake performance after several runs of adsorption-desorption. Additionally, it exhibited more superior uptake performance toward MB than commercial powder activated carbon (PAC) in column adsorption system. Thus, the outstanding sorption ability, unique capture selectivity, as well as excellent stability and recyclability for model wastewater endow it a promising candidate adsorbent for selective adsorption and separation of MB from complex wastewater.

Simultaneous removal of coexisting metals and dyes from industrial wastewaters is challenging, and the mutual effects behind the co-adsorption of these pollutants remain unclear. Herein, interlayer-expanded MoS2 (IE-MoS2) nanosheets prepared by a one-pot simple and scalable method were tested to simultaneously remove toxic metals and cationic dyes. The adsorption capacities of IE-MoS2 nanosheets were 499, 423, 500, 355, and 276 mg/g for Pb(II), Cu(II), methylene blue, malachite green, and rhodamine B, respectively, in a mono-contaminant system. Interestingly, the sequestration amount of Pb(II) was dependent on the concentrations of dyes in the binary Pb(II)-dye systems, while uptake of cationic dyes was almost not influenced by coexisting Pb(II). The simultaneous adsorption mechanism was further confirmed by spectroscopic methods. The IE-MoS2 nanosheets were easily regenerated and reused for six adsorption-desorption cycles without structure destruction, thus avoiding the potential hazards of nanomaterial to the ecosphere. More interestingly, high-efficiency uptake of Pb(II) from intentionally contaminated natural water and model textile effluent was obtained by using a column filled with IE-MoS2 nanosheets. In summary, IE-MoS2 nanosheets with facile and scalable synthesis method, efficient adsorption performance, and excellent reusability showed potential promise for the integrative treatment of complex wastewater bearing both metals and organic pollutants.

This paper is mainly observations on the growth and biomass accumulation of Spirulina subsalsa in modified Zarrouk medium supplemented with complex wastewater (CW, from a monosodium glutamate factory) in different concentrations. High ammonia in 75% and 100% CW inhibits algae growth, but maximum biomass production (2.86mgL(-1)) was obtained in 25% CW (concentration of CW in medium was 25%). Different CW concentration promoted biomass composition accumulation at different degrees, 41% of protein content in 25% CW and 18% of carbohydrate in 50% CW. In terms of economy, a concentration of 25% CW was suitable for protein production and 50% for lipid and carbohydrate production. These results suggested that CW is a feasible replacement in part for cultivation of S. subsalsa to economize input of water and nutrients.