Spectrophotometric determination of hydroxylamine in biological wastewater treatment processes

Hydroxylamine, a very important intermediate in nitrification, has a direct relationship with the production of nitrous oxide in biological wastewater treatment processes. The spectrophotometric method taking ferric ammonium sulfate and 1, 10-phenanthroline as the oxidant and the chromogenic agent, respectively, was used to determine the concentration of hydroxylamine in biological wastewater treatment processes. The impacts of nitrite, nitrate, orthophosphate, calcium ion and trace elements on the method were examined. The results indicated that the spectrophotometric method can be used for the determination of hydroxylamine in biological wastewater treatment processes. The correlation was significant in the range of 0.02–1.00 mg N/L (y = 1.5078x ? 0.0132, R ² = 0.9991), and the range varied to 0.05–1.00 mg N/L when nitrite and orthophosphate presented. Nitrate, calcium ion and trace elements did not interfere with the determination of hydroxylamine nitrogen. When the concentrations of nitrite nitrogen in the samples were lower than 15.00 mg/L, nitrite had a minor interference on the method. The impacts of orthophosphate on the method were complex. When the concentrations of hydroxylamine nitrogen were higher than 0.10 mg/L, the interference of orthophosphate on the method can be ignored. However, when the concentrations of hydroxylamine nitrogen in the samples were lower than 0.10 mg/L, orthophosphate had significant impacts on the determination, and a numerical method proposed can eliminate the interference of orthophosphate. The spectrophotometric method can determine the concentration of hydroxylamine in biological wastewater treatment processes quickly and conveniently and was helpful to understand the function of NH₂OH in N₂O production in biological wastewater treatment processes.     

百花湖水体氮的空间分布研究

初步探讨了百花湖水体中氮的空间分布特征,并分析了氮及溶解氧(DO)的相关性。对8个站位的表层、4m、8m及12m水体中总氮、氨氮、硝酸盐氮、亚硝酸盐氮及溶解氧进行了测定。结果表明,百花湖水体中总氮的平均含量为1.18mg/L,氨氮的平均含量为0.144mg/L,硝酸盐氮的平均含量为0.20mg/L,亚硝酸盐氮的平均含量为0.018mg/L。百花湖入湖口附近的1号采样点总氮、氨氮和硝酸盐氮的平均浓度都较其它采样点高。分析表明百花湖中DO浓度与硝酸盐氮和亚硝酸盐氮呈负相关,相关系数分别为-0.629、-0.724。      

Influence of dissolved oxygen concentration and aeration time on nitrite accumulation in partial nitrification process

This study investigated the influence of dissolved oxygen concentration and aeration time on nitrification and nitrite accumulation in an attempt to optimize the recently developed biological-partial-nitritation process for the treatment of strong nitrogen wastewaters. Investigation of dissolved oxygen concentration on ammonium and nitrite oxidation was carried out in a batch reactor. The dissolved oxygen concentration of 0.5 mg O₂/L inhibited both ammonium as well as nitrite oxidation, while increase of dissolved oxygen concentration to ～1 mg O₂/L increased the ammonium oxidation rate and was comparable to that at higher dissolved oxygen concentrations. Experiments were carried out in a sequencing batch reactor for more than 100 days to investigate the influence of aeration time on nitrite accumulation. The dissolved oxygen concentration was controlled at ～1.0 mg O₂/L (in the range of 0.8–1.5 mg/L) during the aeration stage, and volatile suspended solid was maintained at 2.0 g/L while temperature and pH were 30±1°C and 8.3±0.1, respectively. In a typical cycle, complete nitrification occurred at aeration time longer than 6 h. When the aeration time was reduced to 4 h., ～80 % of partial nitritation was achieved. With a further reduction in aeration time to 3 h., nearly 1:1 nitrite/ammonium ratio was yielded. This result revealed that for the reactor design, aeration time determined by feasibility experiments must be considered based on the nitrogen strength in wastewater and biomass concentration in the reactor with dissolved oxygen concentration of ～1.0 mg O₂/L for satisfactory partial nitrification with subsequent processes such as anaerobic ammonium oxidation.     

Assessment of the impact of industrial effluents on water quality of receiving rivers in urban areas of Malawi

A study was carried out in Malawi to assess the extent of chemical pollution in a receiving river as affected by industrial effluents. Both the effluents and the water at selected points in the river were analysed for pH, dissolved oxygen, biochemical oxygen demand, electrical conductivity, suspended solids, nitrate, alkalinity, hardness, chloride and phosphate in the dry and rainy seasons. The results showed that the effluents were acidic in both the dry season (range: 4.2 ± 0.02–6.5 ± 0.02) and in the rainy season (range: 4.2 ± 0.05–5.6 ± 0.01). While the levels of dissolved oxygen, biological oxygen demand, electrical conductivity, suspended solids, alkalinity and chloride were relatively high in the dry and rainy seasons, the concentration of phosphate and nitrate were low in both seasons. The water upstream was neutral (average pH, 7.40 ± 0.04) with high dissolved oxygen but low in the levels of the other parameters in both seasons. The water after the effluent receiving points was acidic and the levels of the other parameters were high, especially downstream. The results suggested that the water in the river was polluted and not good for human consumption. It is therefore recommended that the careless disposal of the wastes should be discouraged and although the values in some cases were lower than the allowable limits, the continued discharge of the effluents in the river may result in severe accumulation of the contaminants and, unless the authorities implement the laws governing the disposal of wastes, this may affect the lives of the people.     

Pump-and-treat method to remove nitrate from groundwater with liquor as the carbon source

As a common pollutant in groundwater, nitrate poses a significant threat to drinking water safety, especially in rural areas. A feasible solution to this problem must be established. In this study, a simple sand bucket was designed to investigate the capability of denitrification with liquor as the carbon source to remove nitrate from pumped groundwater, and the feasibility of the pump-and-treat method. Results showed that addition of a proper amount of liquor enhanced the growth and metabolism of denitrifying bacteria, efficiently reduced the nitrate content in pumped groundwater, and restricted the accumulation of intermediate products. The removal rate of nitrate exceeded 99% and reached about 16.0 mg/L/day when the carbon-to-nitrogen (C/N) ratio was higher than 0.8. The accumulated concentration of nitrite as an intermediate was less than 1.0 mg/L when the C/N ratio was higher than 1.5. However, acetate accumulation was significant. Considering the accumulation of intermediates, the appropriate range of the C/N ratio should be 1.5–1.8. In addition, onset and maintenance of denitrification were not significantly influenced by dissolved oxygen and pH. The pump-and-treat method can provide a convenient and practical channel for household or collective removal of nitrate from pumped groundwater in rural areas because liquor as a household drink is frequently accessible and inexpensive in many areas.     

Simultaneous application of iron and aluminum anodes for nitrate removal: a comprehensive parametric study

Exposure to high concentration of nitrate through drinking water poses a threat to human health and environment. Electrocoagulation (EC) is an alternative water treatment process that involves electrogeneration of coagulant agents. In the present study, EC was exerted for the nitrate removal in a batch reactor using aluminum and iron anodes simultaneously. The effects of the main parameters including electrical current, initial pH, NaCl dosage, initial nitrate concentration and presence of turbidity on NO₃ ^? removal were investigated. NO₂ ^? as a by-product was monitored during electrolysis, and nitrate–nitrite index was calculated. The results indicated that optimum condition was pH of 5, 300 mA electrical current, 100 mg/L NaCl and electrolysis time of 40 min, under which removal efficiency was 81.5 %. Nitrite anion was generated during electrolysis of nitrate solution which increases nitrate–nitrite index at the first reaction time, and it was eliminated after 20-min electrolysis time. Reaction kinetic of nitrate removal in the absence and presence of turbidity was first-order and zero-order, respectively.     

Characterisation of the physicochemical qualities of a typical rural-based river: ecological and public health implications

The physicochemical qualities of a typical rural-based river were assessed over a 12-month period from August 2010 to July 2011 spanning the spring, summer, autumn and winter seasons. Water samples were collected from six sampling sites along Tyume River and analysed for total nitrogen, orthophosphate, biochemical oxygen demand (BOD), temperature, pH, dissolved oxygen (DO), electrical conductivity (EC), total dissolved solids (TDS) and turbidity. BOD regimes did not differ significantly between seasons and between sampling points and ranged from 0.78 to 2.76 mg/L across seasons and sampling points, while temperature ranged significantly (P < 0.05) between 6 and 28 °C. Turbidity varied significantly (P < 0.05) from 6 to 281 nephelometric turbidity units while TDS (range 24–209 ppm) and conductivity (range 47.6–408 mg/L) also varied significantly (P < 0.05) across sampling points with a remarkable similarity in their trends. Orthophosphate concentrations varied from 0.06 to 2.72 mg/L across seasons and sampling points. Negative correlations were noted between temperature and the nutrients, DO and temperature (r = ?0.56), and TDS and DO (r = ?0.33). Positive correlations were noted between TDS and temperature (r = 0.41), EC and temperature (r = 0.15), and DO and pH (r = 0.55). All nutrients were positively correlated to each other. Most measured parameters were within prescribed safety guidelines. However, the general trend was that water quality tended to deteriorate as the river flows through settlements, moreso in rainy seasons.     

Heavy metal assessment and water quality values in urban stream and rain water

Water quality monitoring in developing countries is inadequate, especially in stream water affected by urban effluents and runoff. The purpose of this study was to investigate heavy metal contaminants in the Nakivubo Stream water in Kampala, Uganda. Water samples Nakivubo Channelized Stream, tributaries and industrial effluents that drain into the stream were collected and analysed for the total elemental concentration using flame atomic absorption spectrophotometer. The results showed that: 1) the wastewater was highly enriched with lead and manganese above the maximum permissible limit; 2) the levels of dissolved oxygen were below the maximum permissible limit, while the biological oxygen demand was above the maximum permissible limit. All industrial effluents/wastewater were classified as strong (> 220 mg/L). Factor analysis results reveal two sources of pollutants; 1) mixed origin or chemical phenomena of industrial and vehicular emissions and 2) multiple origin of lead (vehicular, commercial establishment and industrial). In conclusion, Nakivubo Channelized Stream water is not enriched with heavy metals. These heavy metals (lead, cadmium and zinc) were rapidly removed by co-precipitation with manganese and iron hydroxides and total dissolved solids into stream sediments. This phenomena is controlled by pH in water.     

Hybrid coagulation/ozonation treatment of pharmaceutical wastewater using ferric chloride,polyaluminum chloride and ozone

In recent years, concerns about the occurrence and fate of active pharmaceutical ingredients, solvents, intermediates and raw materials that could be present in pharmaceutical industry effluents have gained increasing attention. Conventional treatment methods, such as activated sludge, are not sufficient enough to remove active pharmaceutical ingredients completely. As a result, complementary treatment methods like coagulation and flocculation are often used and play a critical role in industrial and municipal wastewater treatment. The primary goal of these methods is to destabilize and remove colloidal particles along with other organic/inorganic contaminants. Recently empirical works have considered ozone as the most promising oxidant for the removal of micro-pollutants. The current study examined the effectiveness of coagulation/flocculation process using ferric chloride, polyaluminum chloride, and aluminum sulfate as a reasonable approach to tackle the issue of treating pharmaceutical wastewater. In addition, the results were compared with the process using only ferric chloride that was the coagulant of an actual treatment plant. Then, improvement of the process performance was investigated using ozone as an oxidant. In conclusion, it was found out that polyaluminum chloride presented better performance among two other coagulants and also adding 200 mg/L of polyaluminum chloride can lead to 97–98 % turbidity removal efficiency. Moreover, polyaluminum chloride was capable of reducing most of the environmental parameters such as chemical oxygen demand and total dissolved solid with the removal efficiency of 70 and 68 %, respectively. Additionally, ozonation improved the coagulation process, especially iron ion removal, and dramatically decreased the concentration from 5.68 to 0.19 mg/L.     

Nutrient removal from activated sludge mixed liquor by wastewater protozoa in a laboratory scale batch reactor

The aim of the study was to investigate the nutrient removal rate of three wastewater protozoan isolates. The study was carried out in a laboratory-scale batch reactor for a period of 120 h. in a four batch study. Aliquot samples were withdrawn from the reactor every 24 h. for the analysis of phosphate, nitrate, nitrite, ammonia, chemical oxygen demand, dissolved oxygen and pH, using standard methods. The results obtained in the different batches among the three isolates showed PO₄ ^2? removal rate ranging from 0.04 to 0.52 mg-PO₄ ^2?/L/h. while NO₃ ^? nitrate removal rates ranged from 0.08 to 0.16 mg-NO₃ ^?/L /h. Also NO₂- and NH₃ rates were observed to range between 0.022 and 0.087 mg-NO₂ ^?/L /h. 0.05 and 0.16 mg-NH₃ ^?/L /h, respectively. For the physicochemical parameters, there was no observed COD decrease; rather there was an increase and this was irrespective of isolates and experimental batches. However, dissolved oxygen concentration decreased drastically (below 1 mg/L) at the end of each batch while pH show a decrease after an initial 24 h. period and thereafter increased. This trend was also irrespective of isolates and experimental batches. Overall, the study has been able to show the effect of the test isolates on nutrient removal rates and other physicochemical parameters (COD, DO and pH) in activated sludge mixed liquor.     

Impacts of Human Activities on Groundwater Quality of an Alluvial Aquifer: A Case Study of the Eskişehir Plain, Turkey

Hydrochemical and water-quality (except biological) data obtained through a two-year sampling and analysis program indicate that the highest concentrations of groundwater pollution occur in the central and eastern parts of Eski?ehir city. Groundwater quality degradation outside the urban area results from agricultural activities. The most serious pollution of groundwater in the Eski?ehir plain is from nitrogen compounds (ammonia, nitrite, and nitrate). The concentrations of ammonia, nitrite, and nitrate of the 51 surveyed water wells range from 0.01–1.65 mg/L, 0.01–1.80 mg/L, and 1.1–257.0 mg/L, respectively. Orthophosphate concentrations in groundwater range from 0.01–1.25 mg/L. Considerable seasonal fluctuation in the groundwater quality was observed. In general, the groundwater quality in wet seasons was better than the quality in dry seasons.     

Reciprocal influence of Kürtün Dam and wastewaters from the settlements on water quality in the stream Harşit,NE Turkey

This paper aims to reveal the reciprocal influence of Kürtün Dam and wastewaters from the settlements on the water quality in the stream Har?it, NE Turkey. Several key water-quality indicators were measured: water temperature (T), pH, dissolved oxygen (DO), electrical conductivity, water hardness, chemical oxygen demand (COD), ammonium nitrogen (NH₄ ⁺–N), nitrite nitrogen (NO₂ ^?–N), nitrate nitrogen (NO₃ ^?–N), total Kjeldahl nitrogen (TKN), total nitrogen (TN), orthophosphate phosphorus (PO₄ ^3?–P), and methylene blue active substances (MBAS). The monitoring and sampling studies were conducted every 15 days from March 2009 to February 2010 at two stations selected in the upstream and downstream of the Kürtün Dam. It was concluded that the Kürtün Dam Lake had a high-quality water in terms of T, pH, DO, COD, NH₄ ⁺–N, NO₂ ^?–N and NO₃ ^?–N values, but slightly polluted water with respect to TKN, PO₄ ^3?–P, and MBAS according to the Turkish Water Pollution Control Regulation. The dam improved the stream water quality by increasing the DO concentration, and decreasing the NO₂ ^?–N and PO₄ ^3?–P concentrations thanks to its hydraulic residence time despite the wastewater discharge by the nearby settlements. However, the wastewater discharge deteriorated the stream water quality increasing the COD, NH₄ ⁺–N, NO₃ ^––N, and TN concentrations.     

Trophic status of Vondo and Albasini Dams; impacts on aquatic ecosystems and drinking water

The presence and levels of major nutrients in the water from Vondo and Albasini Dams and their water treatment plants have been assessed to determine trophic status of the dams and impacts on aquatic ecosystems and drinking water. Water quality parameters particularly phosphates and nitrates are critical in assessing the trophic status. Water quality parameters linked to eutrophication and agrochemicals were analyzed. Phosphate was undetectable in both dams. The nitrate levels in Albasini and Vondo Dams which were from 1.16 to 6.65?mg/L and 0.46 to 4.19?mg/L, respectively, were within and above the South African guideline for aquatic ecosystems of 2?mg/L. The raw water pH for Vondo and Albasini Dams were from 6.20 to 7.46 and 6.35 to 8.70, respectively, and were mostly within acceptable guidelines for aquatic ecosystems. The water transparency for Vondo and Albasini Dams were from 0.5 to 4.2?m and 0.4 to 0.9?m, respectively. The levels of all other water quality parameters investigated in both dams and their WTPs mostly indicate low, rarely high and no water quality problems in aquatic ecosystems and drinking water. The low levels of total suspended solids and water transparency, the pH range, low to high electrical conductivity, low to acceptable dissolved oxygen levels, acceptable to high biological oxygen demand and nitrate levels for both dams indicate oligotrophic to eutrophic states. Though oligotrophic state dominates, the mixture of trophic states has been attributed to increase in urbanization and intensive agriculture.     

Determining the genetic origin of nitrate contamination in aquifers of Northern Gujarat,India

Over the past decades, the Gujarat state of India experienced intensive agricultural and industrial activities, fertilizer consumption and abstraction of groundwater, which in turn has degraded the ground water quality. Protection of aquifers from nitrate pollution is a matter of prime concern for the planners and decision-makers. The present study assessed the spatial and temporal variation of groundwater nitrate levels in areas with different land use/land cover activities for both pre- and post-monsoon period. The pre-monsoon nitrate level (1.6–630.7 mg/L) in groundwater was observed to be higher as compared to the post-monsoon level (2.7–131.7 mg/L), possibly due to insufficient recharge and evaporation induced enrichment of agrichemical salts in groundwater. High HCO₃ ^? (200–1,000 mg/L) as well as SO₄ ^2?/Cl^? (0.111–0.992) in post-monsoon period provides a favourable environment for denitrification, and lower the NO₃ levels during the post-monsoon period. The K vs NO₃ scatter plot suggests a common source of these ions when the concentration is <5 mg/L, the relationships between different pollutants and nitrate also suggest that fertilizers and other sources, such as, animal waste, crop residue, septic tanks and effluents from different food processing units present in the area can be attributed to higher nitrate levels in the groundwater. Appropriate agronomic practices such as application of fertilizers based on calibrated soil tests and proper irrigation with respect to crop can minimize the requirement for inorganic fertilizers, which can bring down the cost of cultivation considerably, and also protect groundwater from further degradation.     

污水灌溉土壤及地下水三氮的变化动态分析

取徐州奎河的生活污水进行饱和灌溉实验,由埋设在田间的一对蒸渗仪(地下水位保持在1m)观测,结果表明:污水中含量高达5035mg/L的氨氮进入土壤后,大部分被土壤胶体所吸附,迁移能力差,一般不会直接污染地下水。但污水在下渗时,能淋溶土壤中积存的NO₂-和NO₃-离子,使它们在地下水中的含量迅速增加。污灌以后,随土壤含水量、氧化还原电位和Ph值的变化,氨化作用、硝化作用和反硝化作用依次成为氮素转化的主要机制。污灌10d之内,由于淋溶和硝化作用产生的NO₂-、NO₃-会造成浅层地下水的严重污染。     

Analysis of temporal and spatial variations in groundwater nitrate and development of its pollution plume: a case study in Karaj aquifer

Considering the importance of groundwater resources in water-supply demands in arid and semiarid areas such as Iran, it is essential to investigate the risk of groundwater pollution. Nitrate is one of the main pollutants that penetrate into the groundwater from various sources such as chemical fertilizers, pesticides, and domestic and industrial sewage. Unfortunately currently, nitrate contamination of the aquifers is a serious problem in Iran. The Karaj aquifer is not exempted, and the nitrate pollution zone, with concentrations far beyond the permitted limit (50 mg/L), expands fast. In this paper, the long-term groundwater-quality data (from 2000 to 2013) collected from Alborz Province Water and Wastewater Company were analyzed using ArcGIS10 and statistical software, and the spatial and temporal patterns of nitrate pollution in drinking-water wells in the Karaj plain and effective parameters (such as depth to groundwater level, hydraulic gradient, land use, precipitation, and urban, agricultural and industrial wastewater) were investigated. The authors also investigated the status of nitrate concentration variation using the concepts of geostatistics, based on determinations from 62 to 194 surveyed wells with a suitable distribution across the plain. With respect to the relationship between quality parameters, hydrogeological status of the aquifer and land usage, causes of the increase in the concentration of nitrate in the water and its trend were investigated as well. Results revealed that the nitrate levels in the northern portion of the study area were the highest with maximum concentrations of 181.7 mg/L from 2000 to 2013. Based on nitrate concentration distribution maps, the levels of nitrate increased from 2006 onwards to 26–100 mg/L. Unfortunately from 2008 to 2012, a pollution zone with a nitrate water concentration of 101–150 mg/L has been observed and even a concentration of 180 mg/L has been determined. In 2000, the entire aquifer area has been drinkable but with the increase in nitrate concentration, the area with undrinkable water has expanded to 21% in 2003, 24% in 2005, 33% in 2007, 39% in 2009, 43% in 2011 and 44% in 2013. The results of this study could provide valuable information with on the status of nitrate water concentrations in the Karaj plain which demands proper strategies and qualitative approaches in the future.     

Role of degree of saturation in denitrification of unsaturated sand specimens

Nitrate contamination of groundwater arises from anthropogenic activities, such as, fertilizer and animal manure applications and infiltration of wastewater/leachates. During migration of wastewater and leachates, the vadose zone (zone residing above the groundwater table), is considered to facilitate microbial denitrification. Particle voids in vadose zone are deficient in dissolved oxygen as the voids are partially filled by water and the remainder by air. Discontinuities in liquid phase would also restrict oxygen diffusion and therefore facilitate denitrification in the vadose/unsaturated soil zone. The degree of saturation of soil specimen (S _r) quantifies the relative volume of voids filled with air and water. Unsaturated specimens have S _r values ranging between 0 and 100 %. Earlier studies from naturally occurring nitrate losses in groundwater aquifers in Mulbagal town, Kolar District, Karnataka, showed that the sub-surface soils composed of residually derived sandy soil; hence, natural sand was chosen in the laboratory denitrification experiments. With a view to understand the role of vadose zone in denitrification process, experiments are performed with unsaturated sand specimens (S _r = 73–90 %) whose pore water was spiked with nitrate and ethanol solutions. Experimental results revealed 73 % S _r specimen facilitates nitrate reduction to 45 mg/L in relatively short durations of 5.5–7.5 h using the available natural organic matter (0.41 % on mass basis of sand); consequently, ethanol addition did not impact rate of denitrification. However, at higher S _r values of 81 and 90 %, extraneous ethanol addition (C/N = 0.5–3) was needed to accelerate the denitrification rates.     

石灰岩含水介质中苯系物（BTEX） 生物可降解性判识

    岩溶含水系统遭受石油烃污染的环境问题十分普遍。相对于多孔含水介质,石油烃BTEX在石灰岩含水介质中的生 物可降解性还不确定。为此,本研究开展了BTEX在石灰石和岩溶地下水介质中的静态微元体实验。经过77天的实验检测 分析,结果表明：（1） BTEX化合物在可利用电子受体溶解氧或硝酸盐存在条件下具有生物可降解性;（2） 向系统中补充 电子受体硝酸盐,具有促进生物降解的作用,其对BTEX的去除率可高达94%;（3） 未发现补充硫酸盐能够促进BTEX生物 可降解性;（4） 甲苯和二甲苯容易被生物降解,但苯的去除具有一定的难度。     

Phycoremediation of cyanide from coke–oven wastewater using cyanobacterial consortium

Owing to the presence of several toxic pollutants such as cyanide, phenol, ammonium, coke–oven wastewater is being considered as hazardous stream and needs to be treated properly. In the present study, cyanobacterial consortium of Dinophysis acuminata and Dinophysis caudata, collected from East Kolkata Wetland, was used for the treatment of both synthetic cyanide solution and real coke–oven wastewater. The growth kinetics was studied considering nitrate as substrate. Since consortium showed growth in cyanide solution, a model was proposed considering both nitrate and cyanide as substrates. The simulated data match quite well with experimental ones. Two coke–oven wastewater samples were collected—untreated one from equalization tank and another from secondary clarifier effluent and treated with consortium separately. Lipid was extracted from biomass of native cyanobacterial consortium, biomass treated with raw coke–oven wastewater and biomass treated with secondary clarifier effluents. Fatty acid methyl ester of such lipid samples was analyzed using gas chromatograph.     

Comparison of microbial communities in petroleum-contaminated groundwater using genetic and metabolic profiles at Kyonggi-Do,South Korea

This research has been performed to determine the differences in microbial communities according to physicochemical properties such as concentrations of volatile aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene (BTEX), dissolved oxygen (DO), electron acceptors, etc., in oil-contaminated groundwaters at Kyonggi-Do, South Korea. The properties of bacterial and microbial communities were analyzed by 16S polymerase chain reaction (PCR) denaturing gradient gel electrophoresis (DGGE) fingerprinting method and community-level physiological profiling (CLPP) using Eco-plate, respectively. Based on the DGGE fingerprints, the similarities of bacterial community structures were high with similar DO levels, and low with different DO levels. Whereas the dominant bacterial groups in GW13 (highest BTEX and lowest DO) were acidobacteria, α-proteobacteria, β-proteobacteria, γ-proteobacteria, δ-proteobacteria, and spirochetes, those in GW7 (highest BTEX and highest DO) were actinobacteria, α-proteobacteria, β-proteobacteria, γ-proteobacteria, δ-proteobacteria, and sphingobacteria. Based on the CLPP results, the groundwater samples were roughly divided into three groups: above 4 mg/L in DO (group 1: GW3 and GW7), below 4 mg/L in DO (group 2: GW8, W1, W2, W3, and BH10), and highly contaminated with BTEX (group 3: GW13). Shannon index showed that the microbial diversities and equitabilities were higher in shallower aquifer samples. Overall, this study verified that the greatest influencing factors on microbial/bacterial communities in groundwaters were DO and carbon sources, although BTEX concentration was one of the major factors.