Oxidation And Reduction Potential Research Articles

Diurnal variation of the water quality parameters in the waste stabilization ponds (WSPs) for water treatment of integrated multi-trophic aquaculture (IMTA) ponds with closed re-circulation system

Organic wastes from Floating Fish Cage Aquaculture (FCA) activities have polluted many inland water bodies, from small reservoirs to major lakes in Indonesia. It has become a national priority to restore ecosystem health in Lake Maninjau. The lake has suffered from the harmful effects of approximately 17,000 units of FCA on its surface area. Better FCA practices that would improve its adjacent water quality have been proposed. The FCA should utilize a more excellent net that would confine its waste. Using a connection pump, the wastewater within this net could then be circulated into a wetland system for its water quality improvement. The proposed wetland system consists of a series of Waste Stabilization Ponds (WSP) and Constructed Wetland Compartments. For the initial stage, a study has been conducted to test the performance of the WSP with approximately six days of hydraulic retention time (HRT) to improve water quality from the Integrated Multi-Trophic Aquaculture (IMTA) ponds in the Prototype Laboratory of Research Centre for Limnology-LIPI. Two major problems in IMTA, namely organic deposition and low of dissolved oxygen (DO), especially concerning its diurnal variations in the system, have not been studied yet. Water qualities of the WSP ponds were measured every 2 hours for three days (22-25 May 2019). Water quality parameters measured were pH, conductivity, dissolved oxygen (DO), turbidity, temperature, oxidation and reduction potential (ORP), and total dissolved solids (TDS). A closed re-circulation within the WSP system was then applied for the last two days of the study period. The result showed that DO values in the effluent pond during the day were significantly higher than the night. In the maturation and facultative ponds, DO values difference ranged from 2.5-3 mg/L and 1.1-4.4 mg/L, respectively. The highest DO (5.98 mg/L) was measured in the maturation pond at 3.00 PM and values were lowest almost to 0 mg/L during the first day in the anaerobic ponds. While for turbidity, the highest was observed in the anaerobic ponds for 41 NTU and were decreased to stable values of an average of 5.3 NTU in the maturation pond on the third day. At the end of the observation, marked increase of DO and decrease in turbidity have occurred in the system. A closed recirculation system within WSP can be used as an option to increase the performance of the wetland system.

Oxidative dissolution of nickel matte in dilute sulfuric acid solutions

Nickel matte (Ni3S2) is the most common feedstock for producing nickel oxide and nickel metal in associated refineries. Nickel matte is produced from sulfide or laterite ores, and contains around 73 wt% nickel. This study investigated the dissolution parameters of nickel matte in dilute sulfuric acid media in the presence of air as oxidant with the goal of presenting a cost-effective process for leaching nickel matte. The dissolution experiments were carried out to examine the following effects: air flow rate, stirring speed, S/L ratio, acid concentration, reaction temperature, reaction time and the amount of ferrous sulfate added. Nickel extraction of 90% and cobalt extraction of 80% were achieved using dilute H2SO4 and sparging of air as a source of oxygen. To increase the dissolution percentage of the matte, ferrous sulfate addition was studied and the oxidation and reduction potential (ORP) was measured to investigate the effect of ferrous ions on nickel and cobalt recovery. The highest nickel dissolution percentage (95%) was observed with the initial addition of 1200 mg/L Fe (II). Characterization of samples has been carried out with quantitative X-ray diffraction (XRD) and scanning electron microscopy, along with an energy dispersive system (SEM-EDS).

Aplicação da estatística multivariada no diagnóstico do processo de salinização em açudes do semiárido nordestino, Ceará/Brasil

No estado do Ceará há diversos açudes utilizados para mitigar os impactos das secas para as populações. Entretanto as águas desses açudes estão sendo afetadas por diferentes processos de salinização, afetando sua qualidade e conseqüente uso. Este trabalho refere-se ao estudo dos açudes Trici e Favelas, sub-bacia do Alto Jaguaribe/CE, localizada a Sudeste do Município de Tauá, visando estabelecer um diagnóstico do processo de salinização. Portanto para estabelecer um diagnóstico da causa ou causas da salinização nas bacias hidrográficas dos açudes Favelas e Trici no estado do Ceará, foram geradas informações para as duas bacias. Dentre elas destacam-se as amostragens de águas, nas quais foram abordadas as variáveis temperatura da água (TH2O), condutividade elétrica (CE µS/cm), pH (concentração hidrogeniônica do meio), potencial de oxidação e redução (ORP), sólidos totais dissolvidos (TDS). Para analisar os dos obtidos foram aplicadas estatística univariada e as técnicas estatísticas multivariadas da análise de componentes principais (PCA) e análise discriminante, com auxilio do software PAST 3. Considerando os resultados estatísticos e da análise estatística multivariada das variáveis TH2O, CE µS/cm, pH, ORP e TDS, tanto no na bacia do açude Favelas como do Trici, verifica-se que elas apresentam comportamentos diferentes. Portanto justificando, a influência dos diferentes processos de salinização que estão ocorrendo nas duas bacias.

Evaluation of artificial neural network models for online monitoring of alkalinity in anaerobic co-digestion system

Compared to pH monitoring during the anaerobic digestion process, alkalinity as an indicator could provide earlier warning for instability of digestion process, which is very important for efficient operation of biogas digesters, especially for multiple feeding substances. However, the online monitoring of alkalinity is still unavailable until now. In this study, available online measured parameters such as pH, oxidation and reduction potential (ORP), and electrical conductivity were selected as inputs, and the soft sensor method based on artificial neural network (ANN) was applied for alkalinity modeling to develop an online monitoring strategy. The dataset was obtained from a 6 month continuously operating anaerobic co-digestion system of cow manure, corn straw, and fruit and vegetable waste, and splited randomly by cross-validation. The results show that the optimum ANN model for total alkalinity prediction is 3-2-1 structure based on back propagation-feedforward neural network. The constructed ANN model was proved to be reliable through the predictive accuracy analysis and sensitivity analysis. The coefficient of determination (R2) of 0.9948 was obtained. ORP is the most significant model factor with the highest sensitivity degree. The online alkalinity monitoring may effectively prevent the failure of anaerobic digestion process and improve the anaerobic digestion efficiency practically.

Habitat suitability evaluation of a benthic macroinvertebrate community in a shallow lake

The relations between benthic macroinvertebrate communities and eco-factors usually are nonlinear and highly complex, and are often difficult to evaluate. In this study, canonical correlation analysis (CCA) and a generalized additive model (GAM) were applied to identify the key eco-factors that influence the community characteristics of benthic macroinvertebrates in a shallow water lake--Baiyangdian Lake. The water depth (H), water transparency (secchi disc depth, SD), concentration of chlorophyll-a (Chl-a), water temperature (T), concentration of dissolved oxygen (DO), oxidation and reduction potential (ORP), ammonium nitrogen (NH4-N) and nitrate nitrogen (NO3-N) in water, median particle diameter (D50), ammonium nitrogen in the substrate (NH4-Nsoil), and biomass of macrophytes, are the main eco-factors affecting the spatial distribution and structure of the benthic macroinvertebrate community in the shallow freshwater lake. This study is the first to introduce GAM to habitat suitability evaluation for benthic macroinvertebrates in large shallow lakes, and to use the Margalef index (dM) instead of individual indicator species to indicate diversity variation. Five factors, including H, T, NH4-Nsoil, organic matter (OM) in the substrates, and the biomass of macrophytes, were selected in the optimal model by stepwise regression. The response curves generated by the GAM indicated that the diversity of benthic macroinvertebrates was negatively correlated with H and (NH3-Nsoil) and was positively correlated with T and OM. The response curve showing the relation between taxa diversity and the biomass of macrophytes was unimodal. The current study examined the combined influence of multiple eco-factors on benthic macroinvertebrates, and increased understanding of relations between the benthic macroinvertebrate community and eco-factors in a shallow lake system.

Online measurement of alkalinity in anaerobic co-digestion using linear regression method

Alkalinity is a reliable indicator of process stability in anaerobic digestion system. Total alkalinity (TA) and partial alkalinity (PA) are usually monitored offline as indicators for the status of anaerobic digestion process. In order to online monitor TA and PA, the linear regression method was used as estimator to predict alkalinity via software sensor method. Parameters, namely, pH, oxidation and reduction potential (ORP), and electrical conductivity (EC), were used as input variables. EC was the most significant parameter with TA and PA. Multiple linear regression (MLR) models and simple linear regression models with EC were constructed to predict TA and PA in anaerobic co-digestion system. On the basis of the evaluation of prediction accuracy, the applications of linear regression models were better for monitoring PA than TA. MLR models provided higher accuracy for alkalinity prediction than simple linear regression models. The two MLR models based on single-phase anaerobic digestion system were also feasible to predict TA in anaerobic co-digestion systems. However, the accuracy of these models should be improved by calibrating for broad applications of linear regression method in online alkalinity measurement. Keywords: anaerobic digestion, alkalinity, online measurement, model, linear regression DOI: 10.3965/j.ijabe.20171001.2701 Citation: Bai X, Li Z F, Wang X M, He X, Cheng S K, Bai X F, et al. Online measurement of alkalinity in anaerobic co-digestion using linear regression method. Int J Agric & Biol Eng, 2017; 10(1): 176–183.

Dissolved Inorganic Carbon (DIC) Contents in Middle and Lower Reaches of Lancang River: Related to Water Environments and Dams

Carbon cycle is one of the focuses of climate change, river carbon is an important part, while dissolved inorganic carbon (DIC) has a high proportion of river carbon flux. In this study, we did the research on the Lancang River, an important international river in the southwest of China. Water samples were obtained from 16 sections of the middle and lower reaches of the Lancang River in 2016 (11 months), then we monitored some water quality indicators and DIC content, finally analyzed the temporal-spatial distribution characteristics of DIC and the relationship between DIC content and water environment factors. The results showed that: (1) DIC contents in the middle and lower reaches of the Lancang River varied from 1.1840 mmol/L to 3.1440 mmol/L, with a mean value of about 2.2155 mmol/L. (2) At a time scale, DIC contents of dry season (spring, autumn and winter) were higher than rainy season (summer). At a space scale, DIC contents of the middle and lower reaches of the Lancang River gradually decreased from north to south, and each reservoir had the same characteristics, that is, DIC contents at upstream of the dam was lower than those at downstream of the dam. Compared to other rivers with cascade dams around the world, DIC contents within studied river were at similar level. And the reservoir’s effect of the Lancang River were not obvious, however, DIC contents in the water sampled upstream the dams had a slight stratification. (3) Water temperature, conductivity, turbidity were important factors affecting DIC content of water, and the effect of oxidation and reduction potential (ORP) and pH on DIC was relatively small.

PAH degradation and redox control in an electrode enhanced sediment cap

Capping is typically used to control contaminant release from the underlying sediments. However, the presence of conventional sediment caps will often eliminate or slow natural degradation that might otherwise occur at the surface sediment. The objective of this study was to explore the potential of a novel reactive capping, an electrode enhanced cap for the remediation of PAH contaminated sediment. The study on electrode enhanced biodegradation of PAH in slurries showed that naphthalene concentration decreased from ~1000 μg/L to ~50 μg/L, and phenanthrene decreased from ~150 μg/L to ~30 μg/L in ElectroBioReactor within 4 days, and the copy numbers of PAH degrading genes increased by almost 2 orders of magnitude. In a cap microcosm, two carbon electrodes were emplaced within a sediment cap with an applied potential of 2 V. The anode was placed at the sediment-cap interface encouraging oxidizing conditions. Oxidation and Reduction Potential (ORP) profiles showed redox potential approximately 60-100 mV higher at the sediment-cap interface with the application of voltage than in controls. Vertical profiles of phenanthrene porewater concentration were obtained by PDMS-coated fiber, and results showed that phenanthrene at the depth of 0-0.5 cm below the anode was degraded to ~70% of the initial concentration within 10 weeks. PAH degrading genes showed an increase of approximately 1 order of magnitude at the same depth. The no power controls showed no degradation of PAH. These findings suggest that electrode enhanced capping can be used to control redox potential, provide microbial electron acceptor, and stimulate PAH degradation.

Effects of pH and ORP on microbial ecology and kinetics for hydrogen production in continuously dark fermentation

The microbial structure and kinetic characteristics of the hydrogen producing strains in two fermentative continuous stirred-tank reactors (CSTRs) were studied by controlling pH and oxidation and reduction potential (ORP). The fluorescence in situ hybridization (FISH) tests were conducted to investigate the fermentative performance of Clostridium histolyticum (C. histolyticum), Clostridium lituseburense (C. lituseburense) and Enterobacteriaceae. The experimental results showed that in ethanol-type reactor 1#, the relative abundance of the strains was 48%, 30% and 22%. Comparatively, the relative abundance in butyric acid-type reactor 2# was 24%, 55% and 19% with butyric acids and hydrogen as the main products. The kinetic results indicated that the hydrogen yield coefficients YP/X in both reactors were 8.357 and 5.951l-H2/g, while the coefficients of the cellular yield were 0.0268 and 0.0350g-Cell/g, respectively. At the same biomass, the hydrogen yield in ethanol-type reactors was more than that in butyric acid reactors. However, the cellular synthesis rate in ethanol-type reactors was low when the same carbon source was used.

Genus-specific and phase-dependent effects of nitrate on a sulfate-reducing bacterial community as revealed by dsrB-based DGGE analyses of wastewater reactors

The biogenic production of hydrogen sulfide is a serious problem associated with wastewater treatment. The aim of this study was to investigate the inhibitory effect of nitrate on the dynamics of sulfate-reducing bacteria (SRB) community in a laboratory-scale wastewater reactor, originating from a denitrifying plant using activated sludge. For this purpose, denaturing gradient gel electrophoresis (DGGE) analysis targeting the dsrB (dissimilatory sulfite reductase) gene was used in combination with chemical analyses and measurement of oxidation and reduction potential (ORP). The reactors were initially dosed with 1.0 and 4.0g/L potassium nitrate and anaerobically incubated for 490h. Addition of 4.0g/L nitrate to the reactor was associated with a prolonged inhibition (over 300h, i.e., 12.5days) of sulfate reduction and this was consistent with a rapid decrease in ORP associated with nitrate depletion. The DGGE analysis revealed that nitrate addition remarkably attenuated a distinct group of dsrB related to Desulfovibrio, whereas other dsrB groups were not influenced. Furthermore, another sulfate reduction by Syntrophobacter in the later stages of the incubation period occurred in both reactors (regardless of the nitrate concentration), suggesting that different SRB groups are associated with sulfate reduction at different stages of the wastewater treatment process.

Seasonality of stable carbon and nitrogen isotopes within the pelagic food web of Taihu Lake

Particulate organic matter (POM), dissolved organic matter (DOM), bacteria and cladoceran were sampled seasonally at Zhihugang Estuary and Lake Center in Taihu Lake. The δ 13 C of the four organic matter fractions showed consistent temporal variation, with heaviest values in summer and lower at other times of the year. The cladoceran δ 13 C showed a significant correlation with that of POM, reflecting a heavy dietary dependence on POM during the study period. The bacteria became enriched in 13 C compared with that of DOM throughout the sampling dates, although no significant relationship was found between the two fractions. δ 13 C values of POM, cladoceran and bacteria were all negative significantly correlated with oxidation and reduction potential (ORP), and specific conductivity (SpCond). As for δ 15 N, the seasonal pattern of food web components was variable. The POM δ 15 N signature exhibited the most enriched isotope ratios during the summer months when dissolved inorganic nitrogen (DIN) nutrients were at their lowest concentrations. The consumption of DIN in summer can explain in part the progressive accumulation of heavy nitrogen isotopes during this period. Spatially, δ 13 C and δ 15 N of the food web components were all slightly depleted at Estuary than that at Lake Center during the study period, possibly due to large allochthonous inputs at Zhihugang Estuary. Relatively wide ranges of stable isotopic values from both sites suggest that seasonality should be considered when attempting to establish food web structures in a eutrophic lake.

Determination of heavy metal pollution with environmental physicochemical parameters in waste water of Kocabas Stream (Biga, Canakkale, Turkey) by ICP-AES

Waste water pollution of industrial areas can answer for the serious consequences of one of the most important environmental threats to the future. In this study, inductively coupled plasma-atomic emission spectrometry method (ICP-AES) is proposed to determine heavy metals (Pb, Cu, Cd, Cr, Zn, Al, Fe, Ni, Co, Mn) and major elements (Ca, Mg) in waste water of Kocabas Stream. The concentration of metals in the waste water samples taken from 9 different stations (St.) in Biga-Kocabas Stream in November 2004 (autumn period) were determined after simple pretreatment of samples by the proposed ICP-AES method. An analysis of a given sample is completed in about 15 min for ICP-AES the method. The results of heavy metals concentrations in waste water were found between 0.00001-77.69610 mg l(-1) by the ICP-AES technique. The concentrations of Pb, Cd, Cu, Zn, Cr, Al, Fe, Mn, Ni, Co, Mg and Ca 0.00001 (St.3,6,7) - 0.0087 mg l(-1) (St.9), 0.00001 (St.4-7) - 0.0020 mg l(-1) (St.8), 0.00001 (St.1,3-7,9) - 0.0041 mg l(-1) (St.2), 0.0620 (St.2) - 0.2080 mg l(-1) (St.3), 0.0082 (St.6) - 0.2290 mg l(-1) (St.8), 0.3580 (St.2) - 1.7400 mg l(-1) (St.3), 0.2240 (St.1) - 0.6790 mg l(-1) (St.3), 0.0080 (St.1) - 1.5840 mg l(-1) (St.3), 0.0170 (St.3) - 0.0640 mg l(-1) (St.2), 0.0010 (St.1,4,5,8) - 0.0080 mg l(-1) (St.3), 5.0640 (St.9) - 5.2140 mg l(-1) (St.1) and 43.3600 (St.2) - 77.6961 mg l(-1) (St.9), respectively. Also we measured environmental physicochemical parameters such as temperature, salinity, specific conductivity, total dissolved solid (TDS), pH, oxidation and reduction potential (ORP), and dissolved oxygen (DO) in the waste water at sampling stations.

Degradation of chlorpyrifos contaminated soil by bioslurry reactor operated in sequencing batch mode: bioprocess monitoring

Bioslurry reactor (SS–SBR) was studied for the degradation of chlorpyrifos contaminated soil using native mixed microflora, by adopting sequencing batch mode (anoxic–aerobic–anoxic) operation. Reactor operation was monitored for a total cycle period of 72 h consisting of 3 h of FILL, 64 h REACT, 2 h of SETTLE, and 3 h of DECANT with chlorpyrifos concentrations of 3000 μg/g, 6000 μg/g and 12000 μg/g. At 3000 μg/g of chlorpyrifos concentration, 91% was degraded after 72 h of the cycle period, whereas in the case of 6000 μg/g of chlorpyrifos, 82.5% was degraded. However, for 12000 μg/g of chlorpyrifos, only 14.5% degradation was observed. The degradation rate was rapid at lower substrate concentration and 12000 μg/g of substrate concentration was found to be inhibitory. Chlorpyrifos removal rate was slow during the initial phase of the sequence operation. Half-life of chlorpyrifos degradation ( t 0.5) was estimated to be 6.3 h for 3000 μg/g of substrate, 17.5 h for 6000 μg/g and 732.2 h for 12000 μg/g. Process performance was assessed by monitoring chlorpyrifos concentration and biochemical process parameters viz., pH, oxidation and reduction potential (ORP), dissolved oxygen (DO), oxygen consumption rate (OCR) and microbial count (CFU) during sequence operation. From the experimental data obtained it can be concluded that the rate-limiting step with the bioslurry phase reactor in the process of chlorpyrifos degradation may be attributed to the concentration of substrate present in either soil or liquid phase. Periodic operations (SBR) by varying individual components of substrate with time in each process step place micro-organisms under nutritional changes from feast to famine and maintains a wide distribution in the population of micro-organisms resulting in high uptake of the substrate in the bioslurry reactor.