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Flue gas cadmium emission during sludge incineration damages to the health of humans and ecological environment due to its toxic, persistent, and bioaccumulation. Cadmium removal in flue gas based on microbial induced carbonate precipitation (MICP) was investigated using a denitrifying membrane biofilm reactor (DBR). Cadmium removal efficiency obtained 89.8%. Caenispirillum , Halomonas , Stappia , Thauera were the dominant aerobic denitrifiers, which carried twelve cadmium resistance genes (czcA, czcB, czcC, czcD, cadA, cadC, cmtR, cueR, copZ, ctpC, zipB, zntA), and expressed six cadmium resistant proteins (ZntA, CzcA, CtpA, CopZ, CopR and CopB) and ten denitrifying proteins(NarG, NarH, Nar I, NapA, NapB, NirK, NirS, NorB, NorC, NosZ), those proteins regulated binding, transport, exportation of cadmium and denitrification. The upregulation of nitrate reductase and nitrite reductase indicated that cadmium could promote the reduction of NO 3 - to NO, as shown by an integrated metagenomic and metaproteomic sequencing. Cadmium speciation of biofilms, such as cadmium carbonate, increased in proportion, whereas others, such as organic matter-bound cadmium, decreased. The biological adsorption process would gradually yield to MICP process. The MICP stabilized cadmium in flue gas mainly by precipitating Cd through sodium succinate-induced carbonate precipitation. Flue gas cadmium could transform to cadmium carbonate bioprecipitate; carboxyl, hydroxyl and amine groups in cell surface and humic acid could complex cadmium to form Cd-EPS. Denitrifying bacteria could induce MICP process to stabilize cadmium in flue gas. This provides a green and low-cost DBR process as advanced treatment technology for remove cadmium from flue gas. • The membrane bioreactor achieved cadmium removal in flue gas from sludge incineration. • Denitrifying bacteria could induce MICP process to stabilize cadmium in flue gas. • Cadmium resistance proteins and denitrifying enzymes cope with cadmium stress. • The mechanism for cadmium removal in flue gas was proposed. [ABSTRACT FROM AUTHOR]

Nitrogen oxides (NO x) and chromium can cause harm to human health and ecological environment. An aerobic denitrifying biotrickling filter (DBTF) for simultaneous removal of NO x and chromium from flue gas was investigated. NO x and chromium removal efficiency could reach up to 98 % and 88 %, respectively. Halomonas, Stappia, Pseudomonas and UG_ Peptococcaceae were the core chromium-resistance- denitrifying genus. Anti-oxidative stress proteins (RpoS, SOD, OxyR and catalase) and anti-heavy metal proteins (MntA, FbpA, TorB and ChrE etc.) and the denitrifying enzymes (NarH, NarI, NapA, NapB, NirK, NirS and NorB) involved in the regulation of chromium stress and the reduction of NO x , as shown by 16 S rDNA, metagenomic and metaproteomic sequencing. The biofilm was characterized by FTIR, XPS, EEM, and SEM-EDS. XPS spectra indicated the formation of a chromium carbonate by microbial induced carbonate precipitation. Chromium speciation in biofilm mainly consisted of 52.8 % organic matter bound state, 35.1 % carbonate bound state and 10.7 % exchangeable state. Flue gas chromium could be removed in the form of chromium carbonate bioprecipitate and HA-Cr via complexation of humic acids in extracellular polymeric substances (EPS), biosorption and biodeposition. DBTF was capable of NO x reduction and chromium removal by denitrification. The results provide a new potential for the collaborative control of NO x and heavy metals from flue gas by the DBTF. • The aerobic denitrifying biotrickling filter achieved NO x and chromium removal simultaneously. • Halomonas, Stappia, Pseudomonas were the core chromium-resistance- denitrifying genus • Anti-oxidative proteins and denitrifying enzymes regulate chromium stress and reduction of NO x. • The mechanism of simultaneous NO x and chromium removal by aerobic denitrification was proposed. [ABSTRACT FROM AUTHOR]

Arsenic in flue gas from municipal solid waste incineration can damage to human health and ecological environment. A sulfate-nitrate-reducing bioreactor (SNRBR) for flue gas arsenic removal was investigated. Arsenic removal efficiency attained 89.4%. An integrated metagenomic and metaproteomic investigation showed that three nitrate reductases (NapA, NapB and NarG), three sulfate reductases (Sat, AprAB and DsrAB), and arsenite oxidase (ArxA) regulated nitrate reduction, sulfate reduction and bacterial As(III)-oxidation, respectively. Citrobacter and Desulfobulbus could synthetically regulate the expression of arsenite-oxidizing gene, nitrate reductases and sulfate reducatases, which involved in As(III) oxidation, nitrate and sulfate reduction. A bacterial consortium containing Citrobacter , UG_Enterobacteriaceas , Desulfobulbus and Desulfovibrio could capable of simultaneously arsenic oxidation, sulfate reduction and denitrification. Anaerobic denitrification and sulfate reduction were cocoupled to arsenic oxidation. The biofilm was characterized by FTIR, XPS, XRD, EEM, and SEM. XRD and XPS spectra verified the formation of aarsenic species (As(V)) from flue gas As(III) conversion. Arsenic speciation in biofilms of SNRBR consisted of 77% residual arsenic, 15.9% organic matter-bound arsenic, and 4.3% strongly absorbed arsenic. Flue gas arsenic was bio-stabilized in the form of Fe–As–S and As-EPS through biodeposition, biosorption and biocomplexation. This provides a new way of flue gas arsenic removal using the sulfate-nitrate-reducing bioreactor. [Display omitted] • SNRBR effectively achieved removal of arsenic in flue gas. • Citrobacter and Desulfobulbus were dominated for As oxidation-nitrate-sulfate reduction. • Anaerobic denitrification and sulfate reduction were cocoupled to arsenic oxidation. • N–S-reductases, arsenite oxidase regulate nitrate -sulfate reduction and As oxidation. • Flue gas As 2 O 3 was biostabilized by biosorption and biodeposition. [ABSTRACT FROM AUTHOR]