Feammox process driven anaerobic ammonium removal of wastewater treatment under supplementing Fe(III) compounds.

Ammonium removal in wastewater treatment plants demands large quantities energy input, such as aeration for wastewater and the addition of organics for nitrate reduction. Anaerobic ammonium oxidation coupled to Fe(III) reduction, called Feammox process play a crucial role in natural nitrogen cycle, which has been rarely investigated in the field of wastewater treatment. Besides, Iron-reducing bacteria (FeRB) as function bacteria of Feammox could transfer electrons to iron oxide by oxidizing organics. The possibility of anaerobic ammonium removal coupled with organics should be investigated to assess the potential of Feammox process for conventional wastewater treatment. In this study, five Fe(III) compounds, Fe2O3, Fe3O4, Fe(OH)3, Citrate-Fe and pyrite were supplemented to investigate the effect of iron oxides on ammonium removal in serum bottles with working volume of 100 mL. It was found that ammonium removal efficiency of the Fe2O3 group was the highest. To simulate wastewater treatment process in sewage treatment plant, three Up-flow anaerobic sludge blanket reactors with volume of 250 mL adding Fe2O3 were applied with influent of ammonium and carbon sources. It was found that the organics significantly inhibited the ammonium removal by Feammox process. This was attributed to that carbon sources and ammonium could be used as electron donors for Fe(III) reduction. In addition, this nitrogen removal was also likely related with the iron cycle, i.e., Fe(III) reduction with ammonium oxidation and Fe(II) oxidation with nitrate/nitrite reduction. This study provides a promising alternative technology for anaerobic ammonium removal in wastewater treatment. Optimizing nitrogen removal and carbon sources applied in conventional wastewater plants are required in future.

Electrostimulation enhanced ammonium removal during Fe(III) reduction coupled with anaerobic ammonium oxidation (Feammox) process.

Ammonium removal in wastewater treatment plants requires a large number of energy input, such as aeration and the addition of organics. Alternative, more economical technologies for nitrogen removal from wastewater are required. This study comprehensively investigated the feasible of microbial electricity coupled with Fe(III) reduction promoting the anaerobic ammonium removal. It was found that electrostimulation coupled with Fe(III) reduction (bioelectrochemical systems-Fe(III) (BES-Fe(III)) reactor) enhanced the anaerobic ammonium removal by 50.38% and 38.8% compared with the BES reactor and Fe(III) reactor, respectively. The ammonium removal rate reached the highest value of 80.62 ± 0.26 g N m-3·d-1 in the Fe(III)-BES reactor comparable to conventional wastewater treatment plants (WWWTPs). The improvement of ammonium removal might be the synergistic effect of BES and Feammox process on reaction process and microorganisms. Firstly, the addition of Fe2O3 could improve the electrochemical characteristics by enriching iron-reducing bacterial (FeRB). Secondly, the improved ammonium removal could be due to nitrite generated from Feammox process driving the anodic ammonium oxidation. Additionally, the ammonium removal improvement might be the effect of BES on the Fe2+ leaching so as to accelerate the Fe (II)/Fe(III) cycle. In agreement, higher abundance of FeRB and iron-oxidizing bacteria was detected in the Fe(III)-BES reactor. This study provides a lower energy consumption and operational cost technology compared with the conventional partial nitrification/denitrification, which was more than 800 times less than for the conventional wastewater treatment.

[Optimization and stability of denitrifying-phosphorus removal in a two-sludge system for treating wastewater with low carbon source].

Poly-beta-hydroxybutyrate (PHB) could be efficiently accumulated under optimized conditions in a sequencing batch moving bed biological reactor (SBMBBR), and a high performance of denitrifying phosphorus removal in the reactor could be achieved by coupling with a two-sludge system. Denitrifying phosphorus removal achieved the highest efficiency under influent COD of 200 mg/L, neutral pH and stirring speed of 80 r/min. The removal rates of phosphorus, NO3(-)-N and NO2(-)-N reached 83.7%, 81.4% and above 100%, respectively. High biomass in the SBMBBR is one of keys to improve the performance in removal of nitrogen and phosphorus. When the SBMBBR was conducted under a two-sludge system, stable and high performance was obtained. Removal rates of phosphorus and TN reached 89.2% and 84.5% under the influent COD of 140-170 mg/L and TN of 34-42 mg/L, respectively. In the process, phosphorus content in excess sludge approached to that in the feeding, and other path of phosphorus removal was not found.

[Treatment of wastewater with low carbon source using phosphorus under anaerobic-anoxic conditions denitrifying].

The effects of influent nitrate concentration and its adding modes on denitrifying phosphorus removal in a wastewater with low carbon (COD = 200 mg/L) using a sequencing batch moving bed biofilm reactor (SBMBBR) operated under anaerobic-anoxic conditions was investigated. After the domestication, the percentage of denitrifying phosphorus removing bacteria (DPB) in all phosphorus removing bacteria(PB) increased from 15.7% to 71.3%, indicating that DPB was enriched. Concentration of the influent nitrate had a significant effect on the treatment. At the influent nitrate concentration of 30 mg/L, i. e., C/N = 6.7 : 1, COD, PO4(3-) -P and NO3(-) -N removal increased to 97.8%, 82.0% and 81.2%, respectively, showing an efficient treatment under this low carbon. When the influent nitrate was less or more (20 and 40 mg/L), phosphorous uptake observed was insufficient in the anoxic stage, and poly-beta-hydroxybutyrate (PHB) increased from 2.2 mg/g MLSS in the initial anaerobic stage to 5.1 mg/g MLSS and 3.5 mg/g MLSS, respectively, affecting phosphorous release in the next period. Adding nitrate in one time, two times or continuous mode had little effect on the denitrifying phosphorus removal, but affected the removal rate in the initial anoxic stage.

[Microwave thermal remediation of soil contaminated with crude oil enhanced by granular activated carbon].

The advantage of rapid, selective and simultaneous heating of microwave heating technology was taken to remediate the crude oil-contaminated soil rapidly and to recover the oil contaminant efficiently. The contaminated soil was processed in the microwave field with addition of granular activated carbon (GAC), which was used as strong microwave absorber to enhance microwave heating of the soil mixture to remove the oil contaminant and recover it by a condensation system. The influences of some process parameters on the removal of the oil contaminant and the oil recovery in the remediation process were investigated. The results revealed that, under the condition of 10.0% GAC, 800 W microwave power, 0.08 MPa absolute pressure and 150 mL x min(-1) carrier gas (N2) flow-rate, more than 99% oil removal could be obtained within 15 min using this microwave thermal remediation enhanced by GAC; at the same time, about 91% of the oil contaminant could be recovered without significant changes in chemical composition. In addition, the experiment results showed that GAC can be reused in enhancing microwave heating of soil without changing its enhancement efficiency obviously.

[Selective catalytic reduction of NOx over Pd/CeZr/TiO2/Al2O3 wire-mesh honeycomb catalysts].

Pd/CeZr/TiO2/Al2O3 wire-mesh honeycomb catalyst was prepared by sol-gel and impregnation. Furthermore, selective catalytic reduction of NOx over Pd/CeZr/TiO2/Al2O3 wire-mesh honeycomb catalyst with propylene under lean burn condition was studied. The effects of the concentration of tetra-n-butyl titanate and dipcoat cycles on TiO2 washcoat were studied by SEM, and the effects of Pd concentration, O2 concentration and gas velocity on catalytic activity were investigated. The experimental results showed that the TiO2 washcoat on wire-mesh support is even and crack-free when the support is impregnated in 20.0% tetra- n-butyl titanate sol for 2 cycles. The NOx conversion decreases with Pd concentration increase. When Pd concentration is 0.23%, NOx conversion is highest. NOx conversion increases with oxygen concentration increase in the range of 1.5%-6.0%. However, when oxygen concentration is higher than 6.0%, NOx conversion decreases with increasing oxygen concentration. The NOx conversion decreases with gas velocity increase and its effect is severer at high temperature than low temperature.

[Effect of temperature and denitrifying phosphorus on nitrogen and phosphorous removal in SBMBBR].

The effect of two kinds of temperature conditions (14 degrees C +/- 1 degrees C and 24 degrees C +/- 1 degrees C) on the removal of phosphorus and nitrogen were studied in a sequencing batch moving bed biofilm reactor (SBMBBR). The experiments were performed at the concentrations of COD, nitrogen and phosphorus in the feed fixing at about 450 mg/L, 40 mg/L and 10 mg/L, respectively. The results indicated that under the two temperatures the phosphorus release amounts were 54.7 mg/L, 19.7 mg/L, and the phosphorus removals were 98.3%, 83.4%, and the total nitrogen removals were 87.8%, 98.4%, respectively. It found that PAOs (phosphorus-accumulating organisms) predominated in the biomass and the nitrifying level was low at the lower temperature. However, with increase of temperature, PAOs were no longer the predominant microbial species and the total nitrogen removal efficiency increased. A denitrifying phosphorus experiment was carried out under the mode of anaerobic/anoxic in the SBMBBR after 3 months anaerobic/oxic operation. The results showed the ratio of denitrifying phosphorus removal to total phosphorus removal was about 80%.