Changes In Turbidity Research Articles

A novel MODIS algorithm to estimate chlorophyll a concentration in eutrophic turbid lakes

A novel approach was developed to estimate phytoplankton biomass in eutrophic turbid lakes, using MODIS bands designed for land and atmospheric studies. The Baseline Normalized Difference Bloom Index (BNDBI) uses the difference of remote-sensing reflectance (Rrs, sr−1) at 555nm (band 4) and 645nm (band 1) after baseline correction using bands at 469nm and 859nm: (Rrs′(555)−Rrs′(645))/(Rrs′(555)+Rrs′(645)). BNDBI takes advantage of the Chl-a’s absorption minimum near 572nm and absorption maximum near 667nm. Using data from Lake Chaohu, the index showed a strong relationship with Chl-a concentrations in conditions that would normally saturate more sensitive ocean-color sensors. Extensive field measurements were used to calibrate and validate the algorithm with unbiased root-mean-square-error (URMSE) of 47.9% when compared to in situ Rrs data. A reduced sensitivity to atmospheric effects was accomplished by using a baseline correction approach, anchored at 469nm and 859nm to correct the radiances at 555nm and 645nm. Radiative transfer simulations showed that the algorithm can be applied directly to MODIS Rayleigh-corrected reflectance (Rrc) after adjusting algorithm coefficients (URMSE uncertainty of 56.4% for MODIS Rrc data) for Chl-a concentrations <1000μgL−1. Comparative analyses showed that the index was resistant to changes in turbidity and organic matter concentrations. Theoretical simulations, image comparisons and spectral analyses demonstrated that the index was robust in a range of complex atmospheric and surface conditions, with different aerosol types, optical thickness (τa555), solar/viewing geometry, sun glint and thin clouds. A comparison with other MODIS and MERIS Chl-a algorithms for turbid waters showed that BNDBI provided consistent results with the advantage of using MODIS wavebands that remain unsaturated in high turbidity conditions. The BNDBI opens new possibilities to explore bio-optical dynamics in turbid eutrophic lakes using data from a range of satellite sources.

Severe Weather Effects on Water Quality in Central Arizona

Extreme weather events affect surface water supplies. Water quality measurements in Central Arizona were used to quantify changes in dissolved organic carbon (DOC) and turbidity following dust storms, floods, and drought‐associated wildfires. This article describes specific extreme events, quantifies changes in DOC and turbidity, and discusses the effects of water quality changes on treatment processes and public perceptions of water quality. Study findings show a co‐occurrence of some dust storm events (high particulate matter) and increased surface water turbidity, attenuation of high DOC loads following upper watershed storm events, significant increases in total organic carbon and turbidity following severe flooding in 2005, and differing effects of upland and lowland wildfires on water quality. Finally, a means to mitigate these effects on both perceived and actual water quality by integrating information from radar systems, stream gauge readings, and online water quality analyzers is suggested.

Evaluation of Short-Term CO₂ Passive Sampler for Monitoring Atmospheric CO₂ Levels

In this study, we investigated the applicability of a short-term carbon dioxide (CO₂) passive sampler using turbidity change in a solution containing barium hydroxide (Ba(OH)₂). The mass of CO₂ introduced into the Ba(OH)₂ aqueous solution was strongly correlated (rSUP2/SUP = 0.9565) to the change in turbidity caused by its reaction with the solution. The sampling rates calculated for 1 h and 24 h were 42.4±5.4 mL min—1 and 2.3±0.3 mL min—1, respectively. Both unexposed (blank) and exposed samplers remained stable during the storage period of at least two weeks. The detection limits of the passive sampler for CO₂ were 81.5 ppm for 1 h and 61.5 ppm for 24 h. Based on the results, the passive sampler using the change of turbidity in the Ba(OH)₂ aqueous solution appears to be a suitable tool for measuring short-term atmospheric concentrations of CO₂.

A new approach to the real-time assessment of the clear-sky direct normal irradiance

In a context of sustainable development, interest for concentrating solar power and concentrating photovoltaic technologies is growing rapidly. One of the most challenging topics is to improve solar resource assessment and forecasting in order to optimize power plant operation. Since clear sky defines the nominal operating conditions of the plants, improving their management requires the use in real-time of clear-sky direct normal irradiance (DNI) models. Typically, accuracy is best achieved by considering water vapor and aerosol concentrations in the atmosphere separately. However, measuring such physical quantities is not easy and requires a weather station close to the considered site. When these data are not available, the attenuating effects can be modeled by atmospheric turbidity factors which can be obtained from DNI under clear-sky conditions. So, the main purpose of the present paper is to propose an efficient approach to assess the clear-sky DNI in real time. This approach combines an existing empirical model, proposed by Ineichen and Perez, with a new methodology for the computation of atmospheric turbidity. It takes advantage of the fact that changes in atmospheric turbidity are relatively small throughout the day in comparison to changes in DNI, even when the sky is free of clouds. In the present study, we considered data from two experimental sites (Golden, in the USA, and Perpignan, in France) and used a wavelet-based multi-resolution analysis as a clear-sky DNI detection tool. In addition, we compared the proposed approach with several combinations of empirical models and ways of computing atmospheric turbidity. The first model is a polynomial of the cosine of the solar zenith angle, whereas the two other models use atmospheric turbidity as an additional input. Regarding its calculation, monthly and daily mean values have been considered. Moreover, we defined a procedure in order to evaluate the accuracy of all the considered approaches. This procedure allows changes in DNI caused by clouds to be simulated using a noisy signal applied to clear-sky periods. In both sites, our approach to the real-time assessment of the clear-sky DNI outperforms the other approaches. In the worst case, the mean absolute error is reduced by 8 W m−2 in comparison to the approaches based on monthly mean values of atmospheric turbidity, and reduced by about 30 W m−2 when taking the polynomial-based model as a reference.

Aggregation behavior and reversibility of sulfonated phenol formaldehyde resin

ABSTRACTAggregation behavior of sulfonated phenol formaldehyde (SPF) resin in the presence of different valence salts and solution pH values was studied by measuring the change of dispersion turbidity with time. Electrophoretic mobility and hydrodynamic diameter of SPF resin aggregates were also measured under different salt conditions. Disaggregation behavior of SPF resin aggregates was characterized by manually shaking or ultrasound treatment. The result shows that that the size of SPF molecule aggregates and turbidity of the SPF resin dispersion were increased with the increase of Na+ and Mg2+ concentrations, and accordingly, the dispersion stability of SPF resin was decreased. The effect of Mg2+ on SPF resin molecule aggregation was more sensitive than that of Na+ as Mg2+ has a stronger charge screening effect on the repulsive forces between SPF resin molecules. H+ protonates –O− and – groups on SPF resin molecules, leading to a decrease of surface charge on the molecule; therefore the molecule aggregation was promoted and SPF resin dispersion stability was decreased. The reversibility of SPF resin aggregates was observed. The SPF resin aggregates could be disaggregated under ultrasound treatment. In addition, the disaggregated aggregates could recover to their original size at quiescent conditions.

Abrupt state change of river water quality (turbidity): Effect of extreme rainfalls and typhoons

River turbidity is of dynamic nature, and its stable state is significantly changed during the period of heavy rainfall events. The frequent occurrence of typhoons in Taiwan has caused serious problems in drinking water treatment due to extremely high turbidity. The aim of the present study is to evaluate impact of typhoons on river turbidity. The statistical methods used included analyses of paired annual mean and standard deviation, frequency distribution, and moving standard deviation, skewness, and autocorrelation; all clearly indicating significant state changes of river turbidity. Typhoon Morakot of 2009 (recorded high rainfall over 2000mm in three days, responsible for significant disaster in southern Taiwan) is assumed as a major initiated event leading to critical state change. In addition, increasing rate of turbidity in rainfall events is highly and positively correlated with rainfall intensity both for pre- and post-Morakot periods. Daily turbidity is also well correlated with daily flow rate for all the eleven events evaluated. That implies potential prediction of river turbidity by river flow rate during rainfall and typhoon events. Based on analysis of stable state changes, more effective regulations for better basin management including soil-water conservation in watershed are necessary. Furthermore, municipal and industrial water treatment plants need to prepare and ensure the adequate operation of water treatment with high raw water turbidity (e.g., >2000NTU). Finally, methodology used in the present of this study can be applied to other environmental problems with abrupt state changes.

Effects of Turbidity on Predation Vulnerability of Juvenile Humpback Chub to Rainbow Trout and Brown Trout

Abstract Predation on juvenile native fish by introduced rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta is considered a significant threat to the persistence of endangered humpback chub Gila cypha in the Colorado River in Grand Canyon. Diet studies of rainbow trout and brown trout in Glen and Grand canyons indicate that these species eat native fish, but impacts are difficult to assess because predation vulnerability is highly variable depending on the physical conditions under which the predation interactions take place. We conducted laboratory experiments to evaluate how short-term predation vulnerability of juvenile humpback chub changes in response to changes in turbidity. In overnight laboratory trials, we exposed hatchery-reared juvenile humpback chub and bonytail Gila elegans (a surrogate for humpback chub) to adult rainbow trout and brown trout at turbidities ranging from 0 to 1,000 formazin nephlometric units. We found that turbidity as low as 25 formazin nephlometric units significantly reduced predation vulnerability of bonytail to rainbow trout and led to a 36% mean increase in survival (24–60%, 95% CI) compared to trials conducted in clear water. Predation vulnerability of bonytail to brown trout at 25 formazin nephlometric units also decreased with increasing turbidity and resulted in a 25% increase in survival on average (17–32%, 95% CI). Understanding the effects of predation by trout on endangered humpback chub is important when evaluating management options aimed at preservation of native fishes in Grand Canyon National Park. This research suggests that relatively small changes in turbidity may be sufficient to alter predation dynamics of trout on humpback chub in the mainstem Colorado River and that turbidity manipulation may warrant further investigation as a fisheries management tool.

Cathepsin K induces platelet dysfunction and affects cell signaling in breast cancer - molecularly distinct behavior of cathepsin K in breast cancer.

BackgroundBreast cancer comprises clinically and molecularly distinct tumor subgroups that differ in cell histology and biology and show divergent clinical phenotypes that impede phase III trials, such as those utilizing cathepsin K inhibitors. Here we correlate the epithelial-mesenchymal-like transition breast cancer cells and cathepsin K secretion with activation and aggregation of platelets. Cathepsin K is up-regulated in cancer cells that proteolyze extracellular matrix and contributes to invasiveness. Although proteolytically activated receptors (PARs) are activated by proteases, the direct interaction of cysteine cathepsins with PARs is poorly understood. In human platelets, PAR-1 and −4 are highly expressed, but PAR-3 shows low expression and unclear functions.MethodsPlatelet aggregation was monitored by measuring changes in turbidity. Platelets were immunoblotted with anti-phospho and total p38, Src-Tyr-416, FAK-Tyr-397, and TGFβ monoclonal antibody. Activation was measured in a flow cytometer and calcium mobilization in a confocal microscope. Mammary epithelial cells were prepared from the primary breast cancer samples of 15 women with Luminal-B subtype to produce primary cells.ResultsWe demonstrate that platelets are aggregated by cathepsin K in a dose-dependent manner, but not by other cysteine cathepsins. PARs-3 and −4 were confirmed as the cathepsin K target by immunodetection and specific antagonists using a fibroblast cell line derived from PARs deficient mice. Moreover, through co-culture experiments, we show that platelets activated by cathepsin K mediated the up-regulation of SHH, PTHrP, OPN, and TGFβ in epithelial-mesenchymal-like cells from patients with Luminal B breast cancer.ConclusionsCathepsin K induces platelet dysfunction and affects signaling in breast cancer cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2203-7) contains supplementary material, which is available to authorized users.

The Importance of Excess Poly(N-isopropylacrylamide) for the Aggregation of Poly(N-isopropylacrylamide)-Coated Gold Nanoparticles.

Thermoresponsive materials are generating significant interest on account of the sharp and tunable temperature deswelling transition of the polymer chain. Such materials have shown promise in drug delivery devices, sensing systems, and self-assembly. Incorporation of nanoparticles (NPs), typically through covalent attachment of the polymer chains to the NP surface, can add additional functionality and tunability to such hybrid materials. The versatility of these thermoresponsive polymer/nanoparticle materials has been shown previously; however, significant and important differences exist in the published literature between virtually identical materials. Here we use poly(N-isopropylacrylamide) (PNIPAm)-AuNPs as a model system to understand the aggregation behavior of thermoresponsive polymer-coated nanoparticles in pure water, made by either grafting-to or grafting-from methods. We show that, contrary to popular belief, the aggregation of PNIPAm-coated AuNPs, and likely other such materials, relies on the size and concentration of unbound “free” PNIPAm in solution. It is this unbound polymer that also leads to an increase in solution turbidity, a characteristic that is typically used to prove nanoparticle aggregation. The size of PNIPAm used to coat the AuNPs, as well as the concentration of the resultant polymer–AuNP composites, is shown to have little effect on aggregation. Without free PNIPAm, contraction of the polymer corona in response to increasing temperature is observed, instead of nanoparticle aggregation, and is accompanied by no change in solution turbidity or color. We develop an alternative method for removing all traces of excess free polymer and develop an approach for analyzing the aggregation behavior of such materials, which truly allows for heat-triggered aggregation to be studied.

Effect of phosphorus addition on biofiltration pre-treatment to reduce ultrafiltration membrane fouling

A pilot-scale study investigated the effect of phosphorus addition on a drinking water biofilter used to reduce fouling of an ultrafiltration membrane. Biofiltration without pre-treatment (BFwp) has been shown to be an effective pre-treatment for the removal of natural organic matter (NOM) components that cause membrane fouling. However, the river source used in this study was found to have low phosphorus concentrations that could potentially affect biofilter biomass levels and NOM biodegradation. The river water source (Saugeen River located at Walkerton, Ontario, Canada) had a high total organic carbon (4.34–6.61 mg/L) of primarily humic content, variable turbidity, and seasonal changes in water temperature (9.7–19.9°C) as measured over the study period. Phosphorus was added to the biofilter influent at 0.01 mg P/L, and later at 0.05 mg P/L, over a four-month period. Biofilter activity, NOM removal, and membrane performance were compared to a control system operating under identical conditions but without nutrient addition. Filter biomass measured by ATP and fluorescein diacetate hydrolysis (overall enzyme activity) was stable over time, with no difference between control and phosphorus-amended biofilters. As well, phosphorus addition did not improve the removal of NOM fractions, especially biopolymers that are important for membrane fouling. There was a small initial increase in the removal of dissolved organic carbon and humic substances after phosphorus addition, but this effect diminished over time. The effluent from each biofilter was used to operate an ultrafiltration membrane system using conditions similar to full scale. Membrane fouling for each experiment was measured over 1.5 d, and operating cycles included 30-min permeation followed by backwashing/air sparging. Results showed that there was no difference in hydraulically reversible or irreversible fouling of membranes fed with the effluent from control or phosphorus-amended biofilters. It was found that biofilter nutrient feed requirements are likely site specific, and affected by factors including biomass and NOM characteristics.

Influence of Variable Streamside Management Zone Configurations on Water Quality after Forest Harvest

Streamside management zones (SMZs) are a common best management practice (BMP) used to reduce water quality impacts from logging. The objective of this research was to evaluate the impact of varying SMZ configurations on water quality. Treatments (T1, T2, and T3) that varied in SMZ width, canopy retention within the SMZ, and BMP utilization were applied at the watershed scale to two watersheds each. Watersheds with wider SMZs (T3: 110 ft, 100% canopy retention) and improved crossings were not significantly different from unharvested control (C) watersheds for all parameters except nitrate and diurnal stream temperatures. Changes in total suspended solids, turbidity, nitrate, dissolved oxygen, and maximum stream temperature were detected for watersheds treated with the current recommended minimum SMZ configurations (T1: 55 ft, 50% canopy retention) and watersheds with unharvested SMZs (T2: 55 ft, 100% canopy retention) and improved crossings.

Effects of Turbidity on Foraging Behavior in the Endangered Fountain Darter (Etheostoma fonticola)

Abstract The fountain darter Etheostoma fonticola is a federally endangered species that is associated with primarily clear, spring-fed systems, suggesting even minor changes in turbidity have the potential to affect behavior. We examined the effects of turbidity [control: <1 Nephelometric Turbidity Unit (NTU), minimal turbidity: mean = 8.7 NTU, moderate turbidity: mean = 23.2 NTU, and high turbidity: mean = 74.6 NTU] on the total number of prey items consumed, time to initiate foraging, total prey consumed out of the time left to forage, and number of strikes made per prey items (prey capture success). Our results indicate elevated turbidity significantly affects the number of prey consumed, time to initiate foraging, and total prey consumed out of the time left to forage. Turbidity does not appear to affect prey capture success. These data suggest even a slight elevation in turbidity (≥8.7 NTU) can significantly impair foraging behavior in E. fonticola.

Fluvial biofilm responses to joint changes in nutrients, temperature, turbidity and water velocity: an ex situ experiment

The aim of this study was to explore the responses of the epipelic biofilm of a Pampean stream with little impact from human activity to two environmental conditions, with joint modifications in nutrients, temperature, water velocity and turbidity. The experiment was conducted using artificial channels and lasted five weeks. The biological variables measured included chlorophyll-a content, bacterial biomass, ash-free dry weight, total carbohydrate concentration, total respiratory activity, and biofilm composition. Results show that the species’ composition of the biofilm was affected, although no other structural or metabolic variables measured were. These results highlight the importance of including structural parameters to measure rapid changes in water quality, even when analyzing the effects of co-occurring variables.

The effect of operating parameters on the performance of a biosand filter: a statistical experiment design approach

The influence of three important parameters, namely, pause time, charge volume and influent turbidity on the performance of a biosand filter (BSF) was assessed by employing response surface methodology with a Box-Behnken design. Fifteen runs were conducted in triplicate using a full-scale BSF with a pore volume of 19.6 L, and the performance of the filter was assessed by monitoring total coliforms, Escherichia coli and turbidity of the effluent. Results showed that there was a significant improvement in the microbiological quality of filtered water when the pause time was increased from 12 to 36 h, while it deteriorated as charge volume was increased from 10 to 30 L. The effluent microbiological quality was unaffected by changes in the influent turbidity in the range of 10–50 NTU. Further, effluent turbidity was not significantly affected by the changes in any of the operating parameters, and it remained below 1.5 NTU in all the runs. At optimum conditions of pause time 23 h, charge volume 19.4 L and influent turbidity 32 NTU, bacterial removal exceeded 99.4%. The results show that charging of the filter with about one pore volume of water once a day would be the ideal operating strategy for a BSF.

Evolution of Mid-Atlantic Coastal and Back-Barrier Estuary Environments in Response to a Hurricane: Implications for Barrier-Estuary Connectivity

Assessments of coupled barrier island-estuary storm response are rare. Hurricane Sandy made landfall during an investigation in Barnegat Bay-Little Egg Harbor estuary that included water quality monitoring, geomorphologic characterization, and numerical modeling; this provided an opportunity to characterize the storm response of the barrier island-estuary system. Barrier island morphologic response was characterized by significant changes in shoreline position, dune elevation, and beach volume; morphologic changes within the estuary were less dramatic with a net gain of only 200,000 m3 of sediment. When observed, estuarine deposition was adjacent to the back-barrier shoreline or collocated with maximum estuary depths. Estuarine sedimentologic changes correlated well with bed shear stresses derived from numerically simulated storm conditions, suggesting that change is linked to winnowing from elevated storm-related wave-current interactions rather than deposition. Rapid storm-related changes in estuarine water level, turbidity, and salinity were coincident with minima in island and estuarine widths, which may have influenced the location of two barrier island breaches. Barrier-estuary connectivity, or the transport of sediment from barrier island to estuary, was influenced by barrier island land use and width. Coupled assessments like this one provide critical information about storm-related coastal and estuarine sediment transport that may not be evident from investigations that consider only one component of the coastal system.

The Novel Multiple Inner Primers-Loop-Mediated Isothermal Amplification (MIP-LAMP) for Rapid Detection and Differentiation of Listeria monocytogenes.

Here, a novel model of loop-mediated isothermal amplification (LAMP), termed multiple inner primers-LAMP (MIP-LAMP), was devised and successfully applied to detect Listeria monocytogenes. A set of 10 specific MIP-LAMP primers, which recognized 14 different regions of target gene, was designed to target a sequence in the hlyA gene. The MIP-LAMP assay efficiently amplified the target element within 35 min at 63 °C and was evaluated for sensitivity and specificity. The templates were specially amplified in the presence of the genomic DNA from L. monocytogenes. The limit of detection (LoD) of MIP-LAMP assay was 62.5 fg/reaction using purified L. monocytogenes DNA. The LoD for DNA isolated from serial dilutions of L. monocytogenes cells in buffer and in milk corresponded to 2.4 CFU and 24 CFU, respectively. The amplified products were analyzed by real-time monitoring of changes in turbidity, and visualized by adding Loop Fluorescent Detection Reagent (FD), or as a ladder-like banding pattern on gel electrophoresis. A total of 48 pork samples were investigated for L. monocytogenes by the novel MIP-LAMP method, and the diagnostic accuracy was shown to be 100% when compared to the culture-biotechnical method. In conclusion, the MIP-LAMP methodology was demonstrated to be a reliable, sensitive and specific tool for rapid detection of L. monocytogenes strains.

Removal of Turbidity From Water by Electrocoagulation Technique.

This study search’s the removal of turbidity from water by electrocoagulation technique. Bench scale with continuous flow system was designed the system consists of electrocoagulation reactor with volume (2 L), flocculation basin and sedimentation basin with volumes change due to the change in detention time of electrocoagulation. Aluminum plates (17×8) cm were used (3 plates) as the anode and (4 plates) as the cathode, the spacing between plates was taken (1 cm) and the temperature of water was kept at (25°C). The study investigates the effects of some operating parameters such as, electrical current that ranging from (0.1 – 2) A, detention time of electrocoagulation (1 , 5 , 10 , 20) minutes and initial turbidity variety of the raw water (10 , 25 , 100 , 300) ntu upon the residual turbidity. Experiment result shows that the residual turbidity decrease with increase value of the electrical current for all values of initial turbidity. Also, the residual turbidity decrease with increase time of electrocoagulation for all values of initial turbidity specialy in (0.1 , 0.25 , 0.5) A, when the electrical current increase to (1 , 1.5 , 2) A , the change in residual turbidity was small specialty in time between (10 – 20) minutes. The results also proved that increasing the initial turbidity lead to increase the residual turbidity.

Lipidic nanovesicles stabilize suspensions of metal oxide nanoparticles

We have studied the effect of adding lipid nanovesicles (liposomes) on the aggregation of commercial titanium oxide (TiO2), zinc oxide (ZnO), or cerium oxide (CeO2) nanoparticles (NPs) suspensions in Hepes buffer. Liposomes were prepared with pure phospholipids or mixtures of phospholipids and/or cholesterol. Changes in turbidity were recorded as a function of time, either of metal nanoparticles alone, or for a mixture of nanoparticles and lipidic nanovesicles. Lipid nanovesicles markedly decrease the NPs tendency to sediment irrespective of size or lipid compositions, thus keeping the metal oxide NPs in suspension. Cryo-electron microscopy, fluorescence anisotropy of TMA-DPH and general polarization of laurdan failed to reveal any major effect of the NPs on the lipid bilayer structure or phase state of the lipids. The above data may help in developing studies of the interaction of inhaled particles with lung surfactant lipids and alveolar macrophages.

Compatibility of butorphanol with granisetron in 0.9% sodium chloride injection packaged in glass bottles or polyolefin bags

The stability of admixtures containing butorphanol and granisetron in polyolefin bags and glass bottles stored at 4 and 25 °C was studied. Commercial solutions of butorphanol tartrate and granisetron hydrochloride were combined and further diluted with 0.9% sodium chloride injection to final concentrations of butorphanol tartrate 0.08 mg/mL and granisetron 0.03 or 0.06 mg/mL; the resulting mixtures were packaged in polyolefin bags and glass bottles. The admixtures were assessed for periods of up to 48 hours after storage at 25 °C without protection from room light and up to 14 days at 4 °C with protection from room light. The chemical stability of the admixtures was evaluated by a validated high-performance liquid chromatography (HPLC) method and by measurement of pH values. Solution appearance and color were assessed by observing the samples against room light and dark backgrounds. HPLC analysis demonstrated that the percentages of the initial concentrations of butorphanol and granisetron in the various solutions remained above 97% during the testing period. No changes in color or turbidity were observed in any of the prepared solutions. Throughout this period, pH values remained stable. Admixtures of butorphanol tartrate 0.08 mg/mL and granisetron 0.03 or 0.06 mg/mL in 0.9% sodium chloride injection in polyolefin bags or glass bottles remained stable for 48 hours when stored at 25 °C exposed to room light and for 14 days when stored at 4 °C protected from room light.

Oxygen Demand of Fresh and Stored Sulfide Solutions and Sulfide-Rich Constructed Wetland Effluent.

This study investigated the contribution of hydrogen sulfide to biological oxygen demand (BOD5) and chemical oxygen demand (COD) in wastewater effluents, and documented the effect of storage times and conditions on the BOD5 and COD of pH-adjusted sodium sulfide solutions as well as graywater wetland effluent. Initial COD measurements of sulfide solutions were 84-89% of the theoretical oxygen demand (ThOD), 1.996 mg O2/mg S, whereas unseeded BOD5 measurements were 55-77%. For sulfide solutions, all storage conditions led to declines of >15% (COD, BOD5), and >31% (sulfide). For wetland effluent, storage without headspace was effective in reducing COD losses (3.7%), compared to storage with headspace (17%), and affected changes in turbidity, UVA-254 and pH. The results suggest that storage times and conditions should be controlled and reported when reporting BOD5 and COD of sulfide-rich samples. Wetland models representing sulfate reduction as a method of COD removal may need to be reconsidered.