Performance and microbial community profiles in pilot-scale biofilter for the simultaneous removal of ammonia, iron and manganese at different manganese concentrations.

To accelerate extensive application of biological manganese removal technology, a pilot-scale biofilter for ammonia, iron and manganese removal was constructed to investigate the removal performance and microbial community profiles at different manganese concentrations. When manganese in influent increased from 1 to 10 mg/L, the pollutants were completely removed. Ammonia and iron was slightly changed along the filter depth, while manganese obviously increased. In 0 m of the filter depth, the abundance of Gallionella (iron oxidizing bacteria, IOB) increased, while Crenothrix (IOB) decreased. The abundance of Gallionella (manganese oxidizing bacteria, MnOB) in 0.4 and 0.8 m increased to 16.82% and 12.37%, respectively; and Crenothrix (MnOB) in 0.8 m increased to 19.95%, but decreased to 25.08% in 0.4 m. The abundance of ammonia oxidizing bacteria (AOB, Nitrosococcus) decreased in 0.4 and 0.8 m. The biofilter presented a high ability to remove manganese, and had a broad application prospect.

Performance and microbial community profiles in pilot-scale biofilter for ammonia, iron and manganese removal at different dissolved oxygen concentrations.

Dissolved oxygen (DO) is a significant operational parameter in biological systems. In this study, a pilot-scale biofilter was constructed to investigate the removal efficiency of ammonia, iron and manganese, as well as the microbial community structure evolution at different DO concentrations. Results indicated that when DO decreased from 8 to 4 mg/L, iron and manganese were still completely removed, however the concentration of ammonia in the effluent increased, and exceeded the permitted limit of 0.5 mg/L when DO was about 4 mg/L. The main functional microbes for ammonia and manganese removal were Nitrosomonas and Crenothrix, which was mainly distributed at 0.8 and 0.8 m of the filter bed with a corresponding abundance of 8.61% and 16.87% in sufficient DO considition, respectively; while iron was mainly removed by Crenothrix and Gallionella in 0 m with a corresponding abundance of 30.45% and 9.77%. With the decreasing of DO concentration, iron oxidizing bacteria (IOB, Crenothrix and Gallionella) was not affected, while the abundance of manganese oxidizing bacteria (MnOB, Crenothrix) increased to completely oxidize manganese. However, the amount of ammonia oxidizing bacteria (AOB, Nitrosococcus) at 0.4 and 0.8 m of the filter depth obviously decreased with increased ammonia in the effluent. Kinds of other bacteria which may be related to methane, hydrogen sulfide and organic matter removal, were also found. In addition, small part of archaea was also detected, such as Candidatus Nitrososphaera and Ferroplasma, which could oxdize ammonia and ferrous iron, respectively.

Enhanced dewatering of sludge with the composite of bioflocculant MBFGA1 and P(AM-DMC) as a conditioner.

Bioflocculant MBFGA1 was investigated to be used as a conditioner for sludge dewatering, and the response surface methodology (RSM) was employed to study the enhancing performance of the dewatering process by the composite of MBFGA1 and poly(acrylamide [2-(methacryloyloxy)ethyl]-trimethylammonium chloride) (P(AM-DMC)). Results showed that dry solids (DS) and specific resistance to filtration (SRF) of sludge treated by MBFGA1 alone appeared as 21.7 % and 3.6 × 10(12) m kg(-1), respectively, which were much better than FeCl3, Al2(SO4)3, and polyaluminum chloride (PAC), but poorer than P(AM-DMC) in sludge dewatering. Apart from this, the optimized conditioning process for improving the dewaterability of the sludge conditioned by the composite is MBFGA1 of 1.4 g L(-1), P(AM-DMC) of 0.13 g L(-1), CaCl2 of 56.1 mg L(-1), pH value of 7.5, and agitation speed of 149 rpm. Under this optimal condition, DS and SRF appeared as 29.9 % and 2.2 × 10(12) m kg(-1), respectively. Thus, it is feasible and meaningful to enhance the dewaterability of the sludge by the compound uses of MBFGA1 and P(AM-DMC).

Influence of temperature on performance and mechanism of advanced synergistic nitrogen removal in lab-scale denitrifying filter with biogenic manganese oxides.

Temperature is a significant operational parameter of denitrifying filter (DF), which affects the microbial activity and the pollutants removal efficiency. This study investigated the influence of temperature on performance of advanced synergistic nitrogen removal (ASNR) of partial-denitrification anammox (PDA) and denitrification, consuming the hydrolytic and oxidation products of refractory organics in the actual secondary effluent (SE) as carbon source. When the test water temperature (TWT) was around 25, 20, 15 and 10 °C, the filtered effluent total nitrogen (TN) was 1.47, 1.70, 2.79 and 5.52 mg/L with the removal rate of 93.38%, 92.25%, 87.33% and 74.87%, and the effluent CODcr was 8.12, 8.45, 10.86 and 12.29 mg/L with the removal rate of 72.41%, 66.17%, 57.35% and 51.87%, respectively. The contribution rate of PDA to TN removal was 60.44%∼66.48%, and 0.77-0.96 mg chemical oxygen demand (CODcr) was actually consumed to remove 1 mg TN. The identified functional bacteria, such as anammox bacteria, manganese oxidizing bacteria (MnOB), hydrolytic bacteria and denitrifying bacteria, demonstrated that TN was removed by the ASNR, and the variation of the functional bacteria along the DF layer revealed the mechanism of the TWT affecting the efficiency of the ASNR. This technique presented a strong adaptability to the variation of the TWT, therefore, it has broad application prospect and superlative application value in advanced nitrogen removal of municipal wastewater.

Steel slags for enhanced removal of landfill leachate in a three-dimensional electrochemical oxidation system.

In this study, a three-dimensional electrochemical oxidation system, with steel slags as particle electrodes, was applied to deal with landfill leachate. The characteristics of particle electrodes were investigated by scanning electron microscope (SEM), X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD) measurements. It was found that the steel slag exhibited rough and irregular surface and mainly consisted of SiO2 (Quartz), which indicated the enhanced absorbed and electroconducted abilities. Subsequently, comparative degradation tests between two-dimensional (2D) and three-dimensional (3D) electrochemical oxidation systems were carried out and results indicated removal efficiencies of COD. Moreover, NH4+-N from landfill leachate in 3D system was greatly improved compared with that of 2D system. Besides, operating conditions were also optimized to interelectrode distance of 1 cm, current density of 20 mA·cm-2, initial pH value of 4.4 and steel slag concentration of 0.30 g·mL-1, all of which were determined to guarantee excellent landfill leachate removal efficiency. In addition, a possible removal mechanism for this system was proposed. The introduction of steel slag particle electrodes in three-dimensional electrochemical oxidation system implied the concept for "using waste to treat waste", providing a workable way in pollutant elimination.

Influence of temperature on CODMn and Mn2+ removal and microbial community structure in pilot-scale biofilter.

Test water temperature (TWT) is a significant operational parameter in biofilter. In this study, a pilot-scale biofilter was established to investigate the removal efficiency of CODMn and Mn2+ and the microbial community structure at different TWT. When CODMn and Mn2+ in the influent were 6-8 and 0.9-1.2 mg/L, respectively, the removal rates were 22.61% and 94.28% at the low TWT, while 69.42% and 97.85% at the high TWT, respectively. Biological CODMn and Mn2+ removal followed the first-order reaction, and at the low and high TWT, the k value was 0.00704 and 0.0738 and 0.0313 and 0.113 min-1, respectively. Organic matter oxidizing bacteria (OMOB, Sphingopyxis, Sphingomonas, Amphiplicatus, Novosphingobium, Gemmatimonas, Chryseolinea and Sphingobium) and manganese oxidizing bacteria (MnOB, Hyphomicrobium, Pedomicrobium and Pseudomonas) were coexisted in 0-1.5 m of the biofilter bed at the low and high TWT, and the abundances were not the main factor affecting the removal efficiency, however the activity.

Construction of Bi2O3/CuNiFe LDHs composite and its enhanced photocatalytic degradation of lomefloxacin with persulfate under simulated sunlight.

Advanced oxidation methods based on photocatalysis and sulfate radicals have attached most interest towards contaminant degradation. However, there are a lack of coupling two methods in the field of pollutant degradation. In the present study, a new Bi2O3/CuNiFe LDHs composite was fabricated and it could efficiently activate persulfate (PS) for lomefloxacin (LOM) decomposition under simulated sunlight, in which 84.6% of LOM (10 mg·L-1) was degraded over 40 min with 0.4 g·L-1 of Bi2O3/CuNiFe LDHs composite and 0.74 mM of PS at natural pH. In addition, the Bi2O3/CuNiFe LDHs composite possessed good reusability and stability at least four runs. Moreover, active radical scavenging experiments indicated that hydroxyl radicals (HO·), sulfate radicals (SO4·-), superoxide radicals (O2·-) and hole (h+) were the main radicals under LOM degradation process. Subsequently, the possible degradation intermediates were determined and the decomposition pathways were put forward. At the same time, activated sludge inhibition experiments were performed to assess the variation of toxicity of LOM and its degradation intermediates during oxidation. Finally, possible reaction mechanism of Bi2O3/CuNiFe LDHs composite for PS activation under simulated sunlight was proposed.

Octadecylamine degradation through catalytic activation of peroxymonosulfate by FeMn layered double hydroxide.

A kind of heterogeneous catalyst, FeMn layered double hydroxide (Fe-Mn-LDH), was fabricated by coprecipitation process and used as PMS activator to degrade a novel organic pollutant octadecylamine (ODA). And the X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microcopy (TEM), Mapping and X-ray photoelectron spectra (XPS) measurements were utilized to characterize the fresh and used Fe-Mn-LDH. After a serious of degradation experiments, it was clearly to see that the activator possessed excellent activation property for PMS and was capable of removing 85% ODA (10 mg·L-1) within 25 min obviously higher than pure PMS. Moreover, the effect of some elements (such as PMS consumption, catalyst consistence and initial pH value), different reaction system and catalyst repeatability on ODA degradation were also explored. And by identification of main radical experiment, SO4- and HO were both confirmed the primary radicals. What's more, extra anion and nature organic matter (NOM) addition experiment displayed that NOM, NO3- and CO32- perform a negative effect on ODA degradation but Cl- could promote it. In addition, repeated experiments and metal leaching after degradation showed good stability of Fe-Mn-LDH. Finally, based on the XPS and Gas Chromatography-Mass Spectrometer (GS-MS) technology, the possible degradation mechanism and pathway were proposed.

Distribution and genetic diversity of microbial populations in the pilot-scale biofilter for simultaneous removal of ammonia, iron and manganese from real groundwater.

A pilot-scale biofilter treating real groundwater was developed in this study, which showed that ammonia, iron and manganese were mainly removed at 0.4, 0.4 and 0.8 m of the filter bed, respectively, and the corresponding removal efficiencies were 90.82%, 95.48% and 95.90% in steady phase, respectively. The variation of microbial populations in the biofilter during start-up process was also investigated using high-throughput pyrosequencing (HTP). Results indicated that the main functional microbes for ammonia, iron and manganese removal were Nitrosomonas, Crenothrix and Crenothrix, respectively, which was mainly distributed at 0.8, 0, and 0.8 m of the filter bed with a corresponding abundance of 8.7%, 28.12% and 11.33% in steady phase, respectively. Kinds of other bacteria which may be related to methane, hydrogen sulfide and organic matter removal, were also found. In addition, small part of archaea was also detected, such as Candidatus Nitrososphaera, which plays a role in nitritation.

Characterization and flocculation mechanism of a bioflocculant from hydrolyzate of rice stover.

This study investigated the characterization and flocculation mechanism of a bioflocculant from hydrolyzate of rice stover. Production of the bioflocculant was positively associated with cell growth and a highest value of 2.4 g L(-1) was obtained. During the kaolin suspension flocculation, charge neutralization and inter-particle bridging were proposed as the reasons for enhanced performance. Apart from this, the bioflocculant showed good performances in sludge dewatering and swine wastewater pretreatment. After conditioning by the bioflocculant, dry solids (DS) and specific resistance to filtration (SRF) of the sludge reached 18.4% and 4.8×10(12) m kg(-1), respectively, which were much better than that by conventional chemical flocculants. In the swine wastewater pretreatment, the removal efficiencies of COD, ammonium, and turbidity reached 48.3%, 43.6% and 75.8% at pH 8.0 when the bioflocculant dose was adjusted to 20 mg L(-1).