Low Dissolved Oxygen Conditions Research Articles

Enhanced heme protein expression by ammonia-oxidizing communities acclimated to low dissolved oxygen conditions

This study has investigated the acclimation of ammonia-oxidizing communities (AOC) to low dissolved oxygen (DO) concentrations. Under controlled laboratory conditions, two sequencing batch reactors seeded with activated sludge from the same source were operated at high DO (near saturation) and low DO (0.1 mg O₂/L) concentrations for a period of 220 days. The results demonstrated stable and complete nitrification at low DO conditions after an acclimation period of approximately 140 days. Acclimation brought about increased specific oxygen uptake rates and enhanced expression of a particular heme protein in the soluble fraction of the cells in the low DO reactor as compared to the high DO reactor. The induced protein was determined not to be any of the enzymes or electron carriers present in the conventional account of ammonia oxidation in ammonia-oxidizing bacteria (AOB). Further research is required to determine the specific nature of the heme protein detected; a preliminary assessment suggests either a type of hemoglobin protein or a lesser-known component of the energy-transducing pathways of AOB. The effect of DO on AOC dynamics was evaluated using the 16S rRNA gene as the basis for phylogenetic comparisons and organism quantification. Ammonium consumption by ammonia-oxidizing archaea and anaerobic ammonia-oxidizing bacteria was ruled out by fluorescent in situ hybridization in both reactors. Even though Nitrosomonas europaea was the dominant AOB lineage in both high and low DO sequencing batch reactors at the end of operation, this enrichment could not be linked in the low DO reactor to acclimation to oxygen-limited conditions.

Release Text on the Humus Soil Pellets

In this article, texted the humus soil pellets by means of SEM-EDAX. Analyze the release of organic matter at different dissolved oxygen conditions and the content of TOC changes after being used for different duration. Systematically studied on the physical and chemical properties of the filler and it’s released highly active organic nutrient composition. Further reveals the principle of humus activated sludge process how to deal with the high concentration organic wastewater. The results show that the humus soil pellets has a complex structure and irregular, containing large quantities of animal bone debris and plant fragments, and its main elements are C, Si, O. Three elements of the weight percentage reached 88.69%, atomic hundreds of content reached 93.52%.The humus soil pellets released organic substances at different dissolved oxygen conditions are different. Released substance under low dissolved oxygen conditions are mostly short-chain polar organic functional groups such as methyl, carboxyl and hydroxyl groups.

Responses of crucian carp Carassius auratus to long-term exposure to nitrite and low dissolved oxygen levels

Both nitrite (NO 2 –N) and dissolved oxygen (DO) are key water quality factors and can impact on aquatic animals' health. In this study, juvenile crucian carp Carassius auratus were exposed to different concentrations of NO 2 –N (0, 2.5, and 5 mg L −1 ) and DO (2 and 6 mg L −1 ) for 30 days. Results showed that under low DO conditions there was a decrease in specific growth rate, feeding rate, food conversion efficiency, and protein efficiency ratio. Red blood cell count (RBC) increased significantly with decreasing DO; three-way ANOVA indicated that there was a statistically significant interaction between DO and NO 2 –N on RBC. Hemoglobin content of fish exposed to low DO levels was significantly higher than that in the normal DO. Changes in the enzymatic (SOD and CAT) and non-enzymatic (GSH) antioxidants in fish liver and blood exhibited oxidative stress occurred under the conditions of low DO and high NO 2 –N. ► Under low dissolved oxygen conditions there was a decrease in growth and feeding. ► Red blood cell count increased significantly with decreasing dissolved oxygen. ► There was a significant interaction between dissolved oxygen and nitrite on RBC. ► Hemoglobin content increased significantly with decreasing dissolved oxygen. ► Oxidative stress occurred under low dissolved oxygen and high nitrite.

Control of sludge settleability and nitrogen removal under low dissolved oxygen condition

Low dissolved oxygen (DO) is an energysaving condition in activated sludge process. To investigate the possible application of limited filamentous bulking (LFB) in sequencing batch reactor (SBR), two lab-scale SBRs were used to treat synthetic domestic wastewater and real municipal wastewater, respectively. The results showed that prolonging low DO aeration duration and setting pre-anoxic (anaerobic) phase were effective strategies to induce and inhibit filamentous sludge bulking, respectively. According to the sludge settleability, LFB could be maintained steadily by adjusting operation patterns. Filamentous bacteria content and sludge volume index (SVI) were likely correlated. SVI fluctuated dramatically within a few cycles when around 200 mL·g−1, where altering operation pattern could change sludge settleability in spite of the unstable status of activated sludge system. Energy consumption by aeration reduced under low DO LFB condition, whereas the nitrification performance deteriorated. However, short-cut nitrification and simultaneous nitrification denitrification (SND) were prone to take place under such conditions. When the cycle time kept constant, the anoxic (anaerobic) to aerobic time ratio was determining factor to the SND efficiency. Similarity keeping aerobic time as constant, the variation trends of SND efficiency and specific SND rate were uniform. SBR is a promising reactor to apply the LFB process in practice.

The impact of pipe flow in riparian peat deposits on nitrate transport and removal

AbstractThe effect of preferential flow in soil pipes on nitrate retention in riparian zones is poorly understood. The characteristics of soil pipes and their influence on patterns of groundwater transport and nitrate dynamics were studied along four transects in a 1‐ to >3‐m deep layer of peat and marl overlying an oxic sand aquifer in a riparian zone in southern Ontario, Canada. The peat‐marl deposit, which consisted of several horizontal layers with large differences in bulk density, contained soil pipes that were generally 0.1 to 0.2 m in diameter and often extended vertically for 1 to >2 m. Springs that produced overland flow across the riparian area occurred at some sites where pipes extended to the peat surface. Concentrations of NO3−–N (20–30 mg L−1) and dissolved oxygen (DO) (4–6 mg L−1) observed in peat pipe systems and surface springs were similar to values in the underlying sand aquifer, indicating that preferential flow transported groundwater with limited nitrate depletion. Low NO3−–N concentrations of <5 mg L−1 and enriched δ15N values indicated that denitrification was restricted to small areas of the peat where pipes were absent. Groundwater DO concentrations declined rapidly to <2 mg L−1 in the peat matrix adjacent to pipes, whereas high NO3−–N concentrations of >15 mg L−1 extended over a larger zone. Low dissolved organic carbon values at these locations suggest that supplies of organic carbon were not sufficient to support high rates of denitrification, despite low DO conditions. These data indicate that it is important to develop a greater understanding of pipes in peat deposits, which function as sites where the transport of large fluxes of water with low biogeochemical reaction rates can limit the nitrate removal capacity of riparian zones. Copyright © 2011 John Wiley & Sons, Ltd.

Hierarchical and interactive habitat selection in response to abiotic and biotic factors: The effect of hypoxia on habitat selection of juvenile estuarine fishes

Habitat selection is a shared process among animals where individuals choose areas that differ in biotic and abiotic characteristics to maximize individual fitness. We used manipulative laboratory mesocosm choice experiments to examine hierarchical and interactive relationships influencing this habitat selection process of estuarine fishes. We assessed selection among substrate, dissolved oxygen (DO) concentration, food availability, and predation risk using two common juvenile estuarine fish species, pinfish (Lagodon rhomboides) and Atlantic croaker (Micropogonias undulatus). For both species oxygen concentration greatly influenced selection patterns; fishes strongly avoided low DO conditions, while in higher levels of DO factors such as substrate or food influenced selection patterns. However, both species strongly avoided predators even when alternative habitat was severely oxygen limited. These results suggest that predation risk may be the greatest determinant of habitat selection of the factors considered. Expansion of low DO areas in the world’s oceans is a major anthropogenic disturbance and is rapidly increasing. Assessing impacts of hypoxia on habitat usage of mobile organisms is critical as changes in environmental metrics including predator distribution and DO levels may alter habitat selection patterns disrupting critical ecosystem processes and trophic interactions. Our results indicate that juvenile fishes may forgo emigration from hypoxia due to predation risk. If similar patterns occur for juvenile fishes in estuaries they may potentially suffer from reduced growth, reproductive output, and survivorship.

Effects of Dissolved Oxygen on Fatigue Characteristics of Austenitic Stainless Steel in 0.9wt% Sodium Chloride Solutions

Fatigue life evaluations in low dissolved oxygen conditions have been found to be conservative regarding the prediction of the fatigue strength of biomaterials. However, dissolved oxygen is considered to increase crack propagation rates. It is necessary to observe whether the strength in low dissolved oxygen conditions is higher. In this paper, the authors observed the effects of dissolved gas on the corrosion fatigue characteristics of austenitic stainless steels. Fatigue strength was higher with low dissolved O2 NaCl aq at a stress ratio of R= 0.1. However, fatigue strength did not change with low dissolved O2 NaCl aq at a stress ratio of R= 0.5 because of the effect of work hardening. Cycles to crack initiation were longer and crack growth rates were lower in the low dissolved O2 NaCl aq. The mechanism of decreasing fatigue strength can be explained by the oxidation process during slipping. In conclusion, dissolved oxygen has the effect of accelerating crack propagation processes.

Effects of dissolved oxygen on fatigue characteristics of austenitic stainless steel in 0.9wt% sodium chloride solutions

Fatigue life evaluations in low dissolved oxygen conditions have been considered as conservative in predicting fatigue strengths of biomaterials. However, dissolved oxygen is considered to increase crack propagation rates. It is necessary to observe whether the strength in low dissolved oxygen conditions becomes higher. In this paper, authors observed effects of dissolved gas on corrosion fatigue characteristics of austenitic stainless steels. Fatigue strength becomes higher in low dissolved O2NaClaq. at stress ratio R=0.1. However, fatigue strength did not change in low dissolved O2NaClaq.at stress ratio R=0.5 because of the effect of work hardening. Cycles to crack initiations became longer and crack growth rates became lower in low dissolved O2NaClaq..In conclusion, dissolved oxygen has effects of accelerating crack propagation processes.

Ecology of Polydora cornuta Bosc, 1802 (Spionidae: Polychaeta) in the Eutrophic Port of Fukuyama, with Special Reference to Life Cycle, Distribution, and Feeding Type

Fukuyama Port is a semi-enclosed harbor located in the central region of the Seto Inland Sea. During June 1998, no dissolved oxygen (DO) was present at the bottom layer of the water column. Low DO conditions continued until October, coinciding with a period of high water temperature. A study of the life cycle, distributive characteristics, and feeding type of Polydora cornuta Bosc, 1802, inhabiting the organically polluted port area, was performed. Polydora cornuta which lives in mud tubes in bottom sediments, was found to be unevenly distributed in the innermost part of the port. Taxonomic characteristics are modifications of setiger 5, which includes major heavy spines. Predicted life-cycle duration, based on the 11.5 - 18.2°C temperature of bottom mud during the normal life period for this species, was 40 to 59 days. Appearance of benthic life-stage individuals was limited to winter and spring (i.e., January to May). However, pelagic larval individuals were present throughout the year. The distribution and density of P. cornuta reflected the DO conditions of the bottom layer and sediment. Stable carbon and nitrogen isotope analysis indicated that this species is a suspension feeder.

Integrated real-time monitoring system to investigate the hypoxia in a shallow wind-driven bay

Corpus Christi Bay (Texas, USA) is a shallow wind-driven bay which experiences hypoxia (dissolved oxygen < 2 mg/L) during the summer. Since this bay is a very dynamic system, the processes that control the hypoxia can last on the order of hours to days. Monitoring systems installed on a single type of platform cannot fully capture these processes at the spatial and temporal scales of interest. Therefore, we have integrated monitoring systems installed on three different platform types: (1) fixed robotic, (2) mobile, and (3) remote. On the fixed robotic platform, an automated profiler system vertically moves a suite of water quality measuring sensors within the water column for continuous measurements. An integrated data acquisition, communication and control system has been configured on our mobile platform (research vessel) for synchronized measurements of hydrodynamic and water quality parameters at greater spatial resolution. In addition, a high-frequency radar system has been installed on remote platforms to generate surface current maps for the bay. With our integrated system, we were able to capture evidence of a hypoxic event in summer 2007; moreover, we detected low dissolved oxygen conditions in a part of the bay with no previously reported history of hypoxia.

オーステナイト系ステンレス鋼の0.9wt%食塩水中における疲労特性におよぼす溶存酸素の影響

Fatigue life evaluations in low dissolved oxygen conditions have been found to be conservative regarding the prediction of the fatigue strength of biomaterials. However, dissolved oxygen is considered to increase crack propagation rates. It is necessary to observe whether the strength in low dissolved oxygen conditions is higher. In this paper, the authors observed the effects of dissolved gas on the corrosion fatigue characteristics of austenitic stainless steels. Fatigue strength was higher with low dissolved O2 NaCl aq at a stress ratio of R= 0.1. However, fatigue strength did not change with low dissolved O2 NaCl aq at a stress ratio of R= 0.5 because of the effect of work hardening. Cycles to crack initiation were longer and crack growth rates were lower in the low dissolved O2 NaCl aq. The mechanism of decreasing fatigue strength can be explained by the oxidation process during slipping. In conclusion, dissolved oxygen has the effect of accelerating crack propagation processes.

G0400-3-6 チタン合金Ti-6Al-4Vの0.9wt%食塩水中での疲労き裂進展挙動に及ぼす溶存酸素の影響([G0400-3]機械材料・材料加工部門一般(3):成形性と強度)

The purpose of this research is to observe the effects of oxide films on the surfaces of Ti-6A1-4V alloys to corrosion fatigue characteristics. Ti alloys are widely used in substrates materials of medical implants. Some reports showed the failures of these implants after several year's services. Therefore, authors discuss the crack growth behavior in corrosion environment and observe the fracture mechanism of oxide film in low dissolved oxygen condition. 0.9wt% NaCl corrosion environment accelerates the cycles to crack initiation. Dissolved oxygen has little effects for crack propagation behavior in higher stress level.

Ferrous and Ferric Ion Generation During Iron Electrocoagulation

Our research on arsenate removal by iron electrocoagulation (EC) produced highly variable results, which appeared to be due to Fe2+ generation without subsequent oxidation to Fe3+. Because the environmental technology literature is contradictory with regard to the generation of ferric or ferrous ions during EC, the objective of this research was to establish the iron species generated during EC with iron anodes. Experimental results demonstrated that Fe2+, not Fe3+, was produced at the iron anode. Theoretical current efficiency was attained based on Fe2+ production with a clean iron rod, regardless of current, dissolved-oxygen (DO) level, or pH (6.5-8.5). The Fe2+ remaining after generation and mixing decreased with increasing pH and DO concentration due to rapid oxidation to Fe3+. At pH 8.5, Fe2+ was completely oxidized, which resulted in the desired Fe(OH)3(s)/ FeOOH(s), whereas, at pH 6.5 and 7.5, incomplete oxidation was observed, resulting in a mixture of soluble Fe2+ and insoluble Fe(OH)3(s)/FeOOH(s). When compared with Fe2+ chemical coagulation, a transient pH increase during EC led to faster Fe2+ oxidation. In summary, for EC in the pH 6.5-7.5 range and at low DO conditions, there is a likelihood of soluble Fe2+ species passing through a subsequentfiltration process resulting in secondary contamination and inefficient contaminant removals.

Investigation of river eutrophication as part of a low dissolved oxygen total maximum daily load implementation

In the United States, environmentally impaired rivers are subject to regulation under total maximum daily load (TMDL) regulations that specify watershed wide water quality standards. In California, the setting of TMDL standards is accompanied by the development of scientific and management plans directed at achieving specific water quality objectives. The San Joaquin River (SJR) in the Central Valley of California now has a TMDL for dissolved oxygen (DO). Low DO conditions in the SJR are caused in part by excessive phytoplankton growth (eutrophication) in the shallow, upstream portion of the river that create oxygen demand in the deeper estuary. This paper reports on scientific studies that were conducted to develop a mass balance on nutrients and phytoplankton in the SJR. A mass balance model was developed using WARMF, a model specifically designed for use in TMDL management applications. It was demonstrated that phytoplankton biomass accumulates rapidly in a 88 km reach where plankton from small, slow moving tributaries are diluted and combined with fresh nutrient inputs in faster moving water. The SJR-WARMF model was demonstrated to accurately predict phytoplankton growth in the SJR. Model results suggest that modest reductions in nutrients alone will not limit algal biomass accumulation, but that combined strategies of nutrient reduction and algal control in tributaries may have benefit. The SJR-WARMF model provides stakeholders a practical, scientific tool for setting remediation priorities on a watershed scale.

Nitrogen removal from slaughterhouse wastewater in a sequencing batch reactor under controlled low DO conditions

The aim of this study was to examine nitrogen removal from slaughterhouse wastewater in a laboratory-scale sequencing batch reactor (SBR) operated at low dissolved oxygen (DO) levels under two aeration strategies: intermittent aeration (IA) and continuous aeration (CA). Under the IA strategy, during the aeration periods, the maximum DO was controlled at 10% saturation; under the CA strategy, in the first hour of the react phase, the DO was maintained at 10% saturation, and then it was kept at 2-3% saturation in the remaining react phase. Total nitrogen removals of up to 95 and 91% were achieved under the IA and CA aeration strategies, respectively. It is proposed that in situ measurement of oxygen utilization rates can be used to control the operation of SBRs for nitrogen removal.

Kinetic Modeling of Inhibition of Ammonia Oxidation by Nitrite under Low Dissolved Oxygen Conditions

In recent years the application of partial nitrification techniques has been denoted as very promising. These methods are based on the oxidation of ammonia to nitrite and the inhibition of the nitratation using different strategies. In most cases, this inhibition causes an increase in the concentration of nitrite. However, the effect of high nitrite concentrations under low dissolved oxygen (DO) conditions on the nitrification process is not well understood. In this paper, the effect of ammonia, nitrite, and nitrate concentrations on the nitrification process under low dissolved oxygen concentrations were studied using respirometric techniques. Results showed that the specific oxygen uptake rate (SOUR) followed a Monod-type equation with respect to the DO concentration. The coefficient SOURm was constant with respect to the ammonia, nitrite, and nitrate within the tested concentrations; in addition, KO was constant with respect to ammonia and nitrate but it increased linearly with the nitrite concentratio...

Effects of arsenic speciation and low dissolved oxygen condition on the toxicity of arsenic to a lotic mayfly

The influence of site-specific conditions on contaminant bioavailability and toxicity to benthic invertebrates is a key consideration in the environmental risk assessment process. This is particularly relevant for contaminants with complex speciation chemistries, such as arsenic. The present study addressed uncertainties regarding arsenic toxicity to a mayfly (Baetis tricaudatus) under low dissolved oxygen (DO) conditions characteristic of many contaminated sites. Arsenic toxicity (arsenite, As(III); arsenate, As(V)) to mayfly nymphs was assessed under two DO scenarios (68 and 84% saturation). Arsenic speciation ratios were determined during testing to confirm the nature of arsenic exposure. The present study found that As(III) was more lethal and bioaccumulated to a greater degree in B. tricaudatus compared to As(V), but the sublethal toxicities of the two arsenic species were similar. Nymph growth and development were significantly inhibited after 12 d of exposure to both 1 mg/L of As(III) and As(V). Exposure to arsenic under low DO conditions (6.5 mg/L, 68% saturation) did not significantly affect As(III) or As(V) toxicity and bioaccumulation over 12 d. The DO level of 6.5 mg/L, however, appeared to be marginally lethal to B. tricaudatus. Results indicate that the Canadian arsenic criterion for the protection of aquatic life (5 microg/L) is protective of B. tricaudatus and is low enough to accommodate differences in arsenic toxicity because of the interconversions between As(III) and As(V). These findings provide insight regarding the toxicity and speciation of arsenic under DO conditions considered to be low for this lotic mayfly species and representative of existing conditions at mine sites in northern Canada.

Comparison of wetland and agriculture drainage as sources of biochemical oxygen demand to the San Joaquin River, California

For many years, the San Joaquin River (SJR) has had low dissolved oxygen conditions intermittently during the late summer and early fall. The low dissolved oxygen conditions are impacting critical fish habitat and the SJR is being regulated under a state of California remediation plan that includes the development of a total maximum daily load (TMDL) allocation for oxygen demanding substances. In support of the development of a scientific TMDL allocation, studies are being conducted to characterize water quality in the many tributaries of the SJR. This study identified the sources of biochemical oxygen demand (BOD) in two western tributaries of the SJR, Mud Slough and Salt Slough, and measured the loads of BOD, algae, and ammonia entering the SJR from wetland and agricultural sources. Mud and Salt Sloughs drain the Grassland Watershed. The watershed contains seasonal wetlands, irrigated farmland, and other agricultural lands. This drainage is under close regulatory scrutiny, because it produces a majority of the selenium and boron entering the SJR. In this study, wetland and irrigated agricultural drainage were sampled separately and a comparison was made to determine differences in water quality. In addition, water entering the study area was compared to water exiting the study area to determine the effect of water use in the region on water quality. This study demonstrated that BOD loads from the Grassland Watershed to the SJR were proportional to flow during June–October, the most critical time for dissolved oxygen deficits in the lower SJR. This indicates that Mud and Salt Sloughs are not producing more BOD than other tributaries in the region that are not under close regulatory scrutiny. The BOD concentration of wetland drainage is higher than that of agricultural drainage, but the higher agricultural drainage flows result in a higher mass loading of BOD. Wetland flooding and irrigation of crops both had a negative impact on water quality. Algal growth was identified as the major source of BOD in agricultural drainage and locations where BOD control could potentially be implemented were identified.

Variation in behavioural response to oxygen stress by egg‐tending males of parapatric fluvial and lacustrine populations of a landlocked goby

The behavioural response of egg‐tending males from parapatric fluvial and lacustrine populations of a landlocked goby Rhinogobius sp. (the orange form) to oxygen stress was compared in laboratory experiments. The natural spawning locations of these populations (rapids of tributary rivers and lakeshore of Lake Biwa, respectively) differ in dissolved oxygen concentration and its variability. Males of both populations spent a longer period of time in fanning behaviour under low dissolved oxygen conditions (4·5–5·0 mg l−1), where &gt;90% of eggs without paternal care died before reaching eyed stage, relative to fully saturated dissolved oxygen conditions (8·0–8·5 mg l−1). Lacustrine males, who occasionally encounter oxygen stress (&lt;2 mg l−1) in their natural habitat, fanned eggs for a longer time period than fluvial males. The time difference in fanning behaviour between the two oxygen conditions was greater for lacustrine than fluvial males. Survival rate in the lower oxygen condition was higher for eggs tended by lacustrine males than those tended by fluvial males, probably due to this difference in fanning activity. These results showed that the response to oxygen stress differs between the two populations and, moreover, as both populations behaved adaptively in responding to the reduction in dissolved oxygen, contiguous habitats may have distinct natural selective pressures. It is suggested that regulation of egg fanning activity is strongly favoured by natural selection in unpredictable environments.

Spatio-temporal Fluctuation of Salinity and Dissolved Oxygen in Lake Jusan

This paper presents salinity and dissolved oxygen (DO) variations in the brackish lake, Lake Jusan, Japan, investigated through field measurements and simulation. During 2007 summer, auto-recoding salinity-temperature meters and DO meters were installed at five stations in the lake. The mean retention time of the lake water estimated from inflow river discharge is about three days, so that large fluctuations of salinity were observed in the entire lake, and low DO conditions were observed during mid-summer in spite of the rapid exchange of lake water. Numerical simulation in terms of salinity and DO was conducted using a vertical 1-dimensional model. The result of this simulation revealed that oxygen was consumed in the mid-layer of the lake due to drought river water inflow during the summer.