Comparison of different valent iron on anaerobic sludge digestion:Focusing on oxidation reduction potential,dissolved organic nitrogen and microbial community

This study compared effects of three different valent iron(Fe^(0),Fe(II)and Fe(III))on enhanced anaerobic sludge digestion,focusing on the changes of oxidation reduction potential(ORP),dissolved organic nitrogen(DON),and microbial community.Under the same iron dose in range of 0−160 mg/L after an incubation period of 30 days(d),the maximum methane production rate of sludge samples dosed with respective Fe^(0),Fe(II)and Fe(III)at the same concentration showed indiscernible differences at each iron dose,regardless of the different iron valence.Moreover,their behavior in changes of ORP,DON and microbial community was different:(1)the addition of Fe^(0) made the ORP of sludge more negative,and the addition of Fe(II)and Fe(III)made the ORP of sludge less negative.However,whether being more or less negative,the changes of ORP may show unobservable effects on methane yield when it ranged from−278.71 to−379.80 mV;(2)the degradation of dissolved organic nitrogen,particularly proteins,was less efficient in sludge samples dosed with Fe^(0) compared with those dosed with Fe(II)and Fe(III)after an incubation period of 30 d.At the same dose of 160 mg/L iron,more cysteine was noted in sludge samples dosed with Fe(II)(30.74 mg/L)and Fe(III)(27.92 mg/L)compared with that dosed with Fe^(0)(21.75 mg/L);(3)Fe^(0) particularly promoted the enrichment of Geobacter,and it was 6 times higher than those in sludge samples dosed with Fe(II)and Fe(III)at the same dose of 160 mg/L iron.

Estimation of the Postmortem Interval by Measuring Blood Oxidation‑reduction Potential Values

Accurate estimation of the postmortem interval(PMI)is an important task in forensic practice.In the last half-century,the use of postmortem biochemistry has become an important ancillary method in determining the time of death.The present study was carried out to determine the correlation between blood oxidation-reduction potential(ORP)values and PMIs,and to develop a three-dimensional surface equation to estimate the PMI under various temperature conditions.A total of 48 rabbits were placed into six groups and sacrificed by air embolism.Blood was obtained from the right ventricle of each rabbit,and specimens were stored at 10℃,15℃,20℃,25℃,30℃,and 35℃.At different PMIs(once every 4 h),the blood ORP values were measured using a PB-21 electrochemical analyzer.Statistical analysis and curve fitting of the data yielded cubic polynomial regression equations and a surface equation at different temperatures.Result:The results showed that there was a strong positive correlation between the blood ORP values at different temperatures and the PMI.This study provides another example of using a three-dimensional surface equation as a tool to estimate the PMI at various temperature conditions.

Modeling, Optimization, and Control of Solution Purification Process in Zinc Hydrometallurgy

The solution purification process is an essential step in zinc hydrometallurgy. The performance of solution purification directly affects the normal functioning and economical benefits of zinc hydrometallurgy. This paper summarizes the authors' recent work on the modeling, optimization, and control of solution purification process. The online measurable property of the oxidation reduction potential(ORP) and the multiple reactors, multiple running statuses characteristic of the solution purification process are extensively utilized in this research. The absence of reliable online equipment for detecting the impurity ion concentration is circumvented by introducing the oxidationreduction potential into the kinetic model. A steady-state multiple reactors gradient optimization, unsteady-state operationalpattern adjustment strategy, and a process evaluation strategy based on the oxidation-reduction potential are proposed. The effectiveness of the proposed research is demonstrated by its industrial experiment.

Trophic mode and organics metabolic characteristic of fungal community in swine manure composting

The succession of fungal community,trophic mode and metabolic characteristics were evaluated in 60 days composting of swine manure by high-throughput sequencing,FUNGuild and Biolog method,respectively.The result showed that the ftingal community diversity reached to the highest level(76 OTUs)in the thermophilic phase of composting,then sustained decline to 15 OTUs after incubation.There were 10 fungal function groups in the raw swine manure.Pathotroph-saprotroph fungi reached to 15.91%on Day-10but disappeared on Day-60.Dung saprotroph-undefined saprotroph fungi grown from 0.19%to 52.39%during the treatment.The ftmgal community had more functional groups but the lower substrate degradation rates in the thermophilic phase.The fungal communities on Day-0 and Day-60 had the highest degradation rates of amino acids and polymers,respectively.Redundancy analysis showed that ORP(49.6%),VS/Ash(45.3%)and moisture(39.2%)were the main influence factors on the succession of fungal community in the swine manure composting process.

Advanced nitrogen removal by pulsed sequencing batch reactors (SBR) with real-time control

The feasibility of pH and oxidation reduction potential(ORP)as on-line control parameters to advance nitrogen removal in pulsed sequencing batch reactors(SBR)was evaluated.The pulsed SBR,a novel operational mode of SBR,was utilized to treat real municipal wastewater accompanied with adding ethanol as external carbon source.It was observed that the bending-point(apex and knee)of pH and ORP profiles can be used to control denitrification process at a low influent C/N ratio while dpH/dt can be used to control the nitrification and denitrification process at a high influent C/N ratio.The experimental results demon-strated that the effluent total nitrogen can be reduced to lower than 2 mg/L,and the average total nitrogen(TN)removal effici ency was higher than 98%by using real-time controll strategy.

Aqueous Chemistry of Typical Geothermal Springs with Deep Faults in Xinyi and Fengshun in Guangdong Province,China

This paper investigated aqueous chemistry for two geothermal spring groups responsive and sensitive to flow fluctuations induced by earthquakes. Quake monitorings are favored for their being in residential areas with well-preserved natural flow systems in Xinyi City＇s Xijiang Hot Springs and Fengshun County＇s Shihu Hot Spring. The hot springs are typical in temperatures and flow rates in southern China＇s Guangdong Province. Physical and chemical conditions deep down in the heat sources are important constraints on earthquake, fluid flow, reactive solute transport and heat transfer, but remain challenging to address via field observations and numerical experiments. In this paper, we made daily and annual observations on flow rates, temperature, and/or aqueous chemistry. We employed strontium isotopes as tracers for the water sources, equilibrium phase diagram for K-feldspar and albite stability, and Na-K-Mg diagram for heat reservoir temperatures. The abundant sulfite content in Xi- jiang Hot Springs is discussed. Our main finding are that the deep fault springs are characterized by low reduction-oxidation potential at around -200- -150 mV and relatively large daily flow variations. The resuits provide scientific background features on the field sites regarding earthquake monitoring and predictions and geothermal reservoir.