Biodegradation of mono-. di- and triethylene glycols in river waters under controlled laboratory conditions

The biodegradation of mono-, di- and triethylene glycols has been evaluated in river waters under controlled laboratory conditions. A recently developed method for the direct monitoring of these glycolsat low concentrations indicates that they degrade according to the bacterial state and temperature of the river water. Monoethylene glycol degrades completely at 20°C within 3 days; at normal winter river temperature not exceeding 8°C, monoethylene glycol is degraded partially or completely within 7 days depending on the river. Di- and triethylene glycols will be removed partially or completely within 7 days at 20°C, but for winter conditions of river flow and temperature, degradation will be minimal within this period.     

Biodegradation of nonylphenol polyethoxylates under sulfate-reducing conditions

Biodegradation behavior of nonylphenol polyethoxylates (NPEOs) under sulfate-reducing conditions was investigated. The results showed that NPEOs were readily degraded under sulfate-reducing conditions. These compounds were degraded via sequential removal of ethoxyl units to nonylphenol (NP) without forming carboxylated intermediates under sulfate-reducing conditions. The biodegradation of NPEOs under sulfate-reducing conditions was not inhibited even at very high initial concentrations of NPEOs. The maximum removal rate increased about 1.3 microM d(-1) for each 10 micromol increase in initial concentration. The decrease in temperature caused a sharp decrease in the removal efficiency of NPEOs. The temperature coefficient (Phi) for the biodegradation of NPEOs under sulfate-reducing conditions was 0.008. Severe accumulation of NP and short-chain NPEOs occurred when most NPEOs were removed and this accumulation led to an increase in the estrogenic activity. The highest estrogenic activity appeared on day 21 when the total concentration of these metabolites reached its top (18.03+/-4.73 microM). NP could inhibit the biodegradation of NPEOs under sulfate-reducing conditions only at relatively high concentration. These findings are of major environmental importance in terms of the environmental behavior of NPEO contaminants in natural environment.     

Biodegradation of domestic wastewater under the simulated conditions of Thailand

Serious concerns have been raised about the sustainability of conventional mechanized linear wastewater treatment systems in the developing world. Bangkok in Thailand is no exception to these concerns, and merits closer examination. This paper is aimed at unveiling the fundamental facts and characteristics relating to the organic degradation potentials of domestic wastewater in Bangkok. It is supported by evidence from simple laboratory experiments in which existing local conditions were simulated. The results showed that greywater‐like qualities of domestic wastewater do predominate in Bangkok, most probably as a result of three main factors: (1) continued use of leaching septic tanks, (2) the tradition of using water after defecation, instead of toilet paper, and (3) high organic degradation potentials under tropical monsoon conditions. Considering the small organic content, coupled with high organic degradation rates of the freshly collected greywater‐based sewage in Bangkok, low‐cost and decentralized natural treatment systems could be far more suitable for environmental sustainability in such tropical monsoon areas than the implementation of large‐scale sewage works.     

Biodegradation of three selected benzotriazoles under aerobic and anaerobic conditions

We examined the biodegradability of three benzotriazoles (benzotriazole: BT, 5-methylbenzotriazole: 5-TTri and 5-chlorobenzotriazole: CBT) under aerobic and anaerobic (nitrate, sulfate, and Fe (III) reducing) conditions. All three benzotriazoles were degraded by microorganisms under aerobic and anaerobic conditions. Both the biodegradation efficiency and biodegradation products were dependent on the predominant terminal electron-accepting condition. Among the redox conditions studied, the shortest biodegradation half lives for BT and 5-TTri were 114 days and 14 days, respectively, under aerobic condition. The shortest half-life for CBT was 26 days under Fe (III) reducing condition. The longest biodegradation half lives for BT and CBT were 315 days and 96 days, respectively, under sulfate reducing condition, while that of 5-TTri was 128 days under nitrate reducing condition. These results suggest that aerobic biodegradation is the dominant natural attenuation mechanism for BT and 5-TTri, while the most favorable process for CBT was anaerobic biodegradation. This study demonstrated that different predominant terminal electron-acceptors present in natural environment play a key role on the biodegradation of BT, 5-TTri and CBT, leading to specific biodegradability. This could have significant implications on in-situ biodegradation of the selected benzotriazoles in aerobic and anaerobic waters, soils and sediments.     

Persistence of four s-triazine herbicides in river, sea and groundwater samples exposed to sunlight and darkness under laboratory conditions

The persistence of terbuthylazine, simazine, atrazine and prometryn (s-triazine herbicides) was studied in sea, river and groundwaters during long-term laboratory incubation (127 days) under different laboratory conditions (light-darkness at 20 degrees C). Analysis of herbicides was performed by GC-NPD and their identity was confirmed by GC-MSD. A micro on-line method for the isolation of herbicide residues was used. The results showed that light had little effect on the removal of the four herbicides in riverwater but had a marked effect on their removal from sea and groundwater. Surprisingly, this removal appeared to be inversely proportional to the concentration of dissolved organic materials. In general, the degradation order was similar in sea and riverwaters; simazine was the most readily degraded compound (t(1/2)= 29-49 days), while terbuthylazine was the most persistent with the longest half-lives (76-331 days). In groundwater, terbuthylazine also showed greater persistence but prometryn was the compound with a fastest degradation rate, half-lives ranged from 88 days for prometryn to approximately 100 days for the other three compounds in light conditions and 263-366 days for prometryn and terbuthylazine, respectively, in darkness. Only for terbuthylazine was the remaining percentage at the end of the experiment higher than 50% under light conditions in riverwater, while in the other cases, the remaining percentage varied from 7 to 43% for simazine in seawater and atrazine in groundwater, respectively. Finally, a greater persistence was observed in groundwater for the four compounds.     

Biodegradation of agricultural herbicides in sequencing batch reactors under aerobic or anaerobic conditions

This study investigated the biodegradability of the herbicides isoproturon and 2,4-dichlorophenoxyacetic acid (2,4-D) in sequencing batch reactors (SBRs). Two laboratory-scale (2L liquid volume) SBRs were employed: one reactor performing under aerobic and the other under anaerobic conditions. The aerobic SBR was operated at an ambient temperature (22+/-2 degrees C), while the anaerobic SBR was run in the lower mesophilic range (30+/-2 degrees C). Each bioreactor was seeded with a 3:1 mixture (by weight) of fresh sludge and biomass that had been previously exposed to both herbicides. The effect of herbicide concentration on either treatment process was explored at a hydraulic retention time (HRT) of 48 h, using glucose as a supplemental carbon substrate. Although no isoproturon degradation was observed in either system during the study, complete 2,4-D removal occurred after an acclimation period of approximately 30 d (aerobic SBR) and 70 d (anaerobic SBR). The aerobic reactor achieved complete 2,4-D utilization at feed concentrations up to 500 mg/L. A further increase to 700 mg/L, however, proved to be inhibitory since 2,4-D biodegradation was negligible. On the other hand, the anaerobic SBR was able to degrade 120 mg/L of 2,4-D, which corresponds to 40% of the maximum feed concentration applied. Moreover, glucose was consumed first throughout the experiment in a sequential utilization pattern relating to 2,4-D, with biodegradation of both substrates following closely first-order kinetics.     

Reproducing stone monument photosynthetic-based colonization under laboratory conditions

In order to understand the biodeterioration process occurring on stone monuments, we analyzed the microbial communities involved in these processes and studied their ability to colonize stones under controlled laboratory experiments. In this study, a natural green biofilm from a limestone monument was cultivated, inoculated on stone probes of the same lithotype and incubated in a laboratory chamber. This incubation system, which exposes stone samples to intermittently sprinkling water, allowed the development of photosynthetic biofilms similar to those occurring on stone monuments. Denaturing gradient gel electrophoresis (DGGE) analysis was used to evaluate the major microbial components of the laboratory biofilms. Cyanobacteria, green microalgae, bacteria and fungi were identified by DNA-based molecular analysis targeting the 16S and 18S ribosomal RNA genes. The natural green biofilm was mainly composed by the Chlorophyta Chlorella, Stichococcus, and Trebouxia, and by Cyanobacteria belonging to the genera Leptolyngbya and Pleurocapsa. A number of bacteria belonging to Alphaproteobacteria, Bacteroidetes and Verrucomicrobia were identified, as well as fungi from the Ascomycota. The laboratory colonization experiment on stone probes showed a colonization pattern similar to that occurring on stone monuments. The methodology described in this paper allowed to reproduce a colonization equivalent to the natural biodeteriorating process.     

实验室条件下淡水藻类生长影响因素研究

为研究淡水藻类生长的最适环境条件和各种环境因素对藻类生长的影响,进行了以水体营养盐、水温和光照为影响因素,以叶绿素a含量为评价指标的正交试验.结果表明,在试验所设定的水平范围内,营养盐浓度、水体温度对淡水藻类生长的影响不显著,光照对淡水藻类生长影响显著;三因素对淡水藻类生长的影响大小排序依次为光照>温度>营养盐浓度;在富营养化水平下,水体营养盐浓度在TN＞1.4 mg/L,TP＞0.1 mg/L的条件下,水体营养盐将不是藻类生长的限制性因素.     

Loss of infectivity of poliovirus 1 in river water under simulated field conditions

The effects of light, virus concentration, and turbidity on the rate of loss of infectivity (LOI) of poliovirus 1 were investigated in two test systems, which utilized flowing river water. Two levels of each variable were used in a 2³ confounded factorial design. The seeded systems were sampled at regular intervals to establish LOI rates. Virus infectivity was measured by plaque assay. Loss of infectivity followed a two-component curve; an initial, rapid phase followed by a second, slower component. The slopes of the two components were examined by the analysis of variance to determine the potential influence of each variable. Both light and turbidity exerted a significant influence on the LOI rate in the second component of the LOI curve and also in the transition period between the two components; however, during the initial, rapid phase none of the variables influenced the LOI rate (at the 0.05 significance level). This research demonstrates the significance of light as a virucidal component in the aquatic environment.     

Determination of cationic surfactants in waste- and river waters

Three analytical methods were used to determine the concentration of ditallow dimethyl ammonium chloride (DTDMAC), a cationic surfactant in river water, sewage influent and sewage effluent. The methods consist of (a) high performance liquid chromatography (HPLC) coupled with conductimetric detection, (b) a colorimetric procedure commonly referred to as disulfine blue active substance (DBAS) and (c) a combination of DBAS and thin-layer chromatography (TLC).The results from this comparison showed that the DBAS procedure was less specific and sensitive than either DBAS-TLC or HPLC and therefore tended to overestimate the concentration of DTDMAC in environmental samples. It also showed DBAS-TLC and HPLC to be comparable in specificity although HPLC is more sensitive and requires significantly less time to perform than either DBAS or DBAS-TLC. The overall advantages of the HPLC procedure make it an attractive analytical technique to accurately measure the concentration of DTDMAC in the environment.     

Silver complexation in river waters of central New York

The dissolved component of the apparent silver complexation capacity was determined for Susquehanna and Chenango River water samples collected over a 3-month period in the vicinity of Binghamton, New York. Silver ion activities detected by the Ag⁺/S^2? ion selective electrode during potentiometric titration of the river water with AgNO₃ were lower than Ag⁺ activities calculated with an inorganic equilibrium speciation model. The maximum difference in Ag⁺ activity, which ranged from 1.5 × 10^?8 to 8.4 × 10^?8, was attributed to the presence of a constituent or constituents in the river water which strongly bind Ag, perhaps dissolved organic matter and/or colloidal material. Variation in apparent complexation capacity between river water samples was explained by different concentrations of the ligands complexing Ag. A tentative extrapolation of the dissolved Ag speciation to Ag concentrations in natural river water suggested that most of the Ag would be complexed by Cl^? and an unidentified constituent or constituents.     

Gaseous elemental mercury emissions and CO2 respiration rates in terrestrial soils under controlled aerobic and anaerobic laboratory conditions

Mercury (Hg) levels in terrestrial soils are linked to the presence of organic carbon (C). Carbon pools are highly dynamic and subject to mineralization processes, but little is known about the fate of Hg during decomposition. This study evaluated relationships between gaseous Hg emissions from soils and carbon dioxide (CO₂) respiration under controlled laboratory conditions to assess potential losses of Hg to the atmosphere during C mineralization. Results showed a linear correlation (r² = 0.49) between Hg and CO₂ emissions in 41 soil samples, an effect unlikely to be caused by temperature, radiation, different Hg contents, or soil moisture. Stoichiometric comparisons of Hg/C ratios of emissions and underlying soil substrates suggest that 3% of soil Hg was subject to evasion. Even minute emissions of Hg upon mineralization, however, may be important on a global scale given the large Hg pools sequestered in terrestrial soils and C stocks.We induced changes in CO₂ respiration rates and observed Hg flux responses, including inducement of anaerobic conditions by changing chamber air supply from N₂/O₂ (80% and 20%, respectively) to pure N₂. Unexpectedly, Hg emissions almost quadrupled after O₂ deprivation while oxidative mineralization (i.e., CO₂ emissions) was greatly reduced. This Hg flux response to anaerobic conditions was lacking when repeated with sterilized soils, possibly due to involvement of microbial reduction of Hg²⁺ by anaerobes or indirect abiotic effects such as alterations in soil redox conditions. This study provides experimental evidence that Hg volatilization, and possibly Hg²⁺ reduction, is related to O₂ availability in soils from two Sierra Nevada forests. If this result is confirmed in soils from other areas, the implication is that Hg volatilization from terrestrial soils is partially controlled by soil aeration and that low soil O₂ levels and possibly low soil redox potentials lead to increased Hg volatilization from soils.     

Organically-bound copper in lake and river waters in Japan

Organically-bound copper, organic matter concentrations and molecular weight of the organic matter in lake and river waters at Hokkaido in Japan were measured. The interaction between copper and the organic matter was also investigated by using Sephadex gel. The ratio of organicallybound copper to total copper was 10–70%. There was no relationship between the copper complex and the organic matter. From thermodynamic calculation, it was concluded that the variation of the ratio from 10 to 70% depended on the variation of stability constant of copper with the organic matter. The organic matter has molecular weight of 300–700 which resembles fulvic acid originating in river water.     

Biodeterioration of sandstone under the influence of different humidity levels in laboratory conditions

Excessive moisture in building materials supports microbial growth. It has been referred that relative humidity more than 55% promotes the microbial growth. To test the effect of different relative humidity tropical chamber test was set up at 52%, 76%, 85% and 96% RH and maximum diversity of fungi was found at 85% and 96% RH. Two fungi Aspergillus sydowi and Aspergillus flavipes were present throughout the course of study from moderate to highly abundant form. It was observed that Fusarium moniliforme, Cephalosporium acremonium, Papulospora sp. proliferated at higher relative humidity (i.e. at 85% and 96.6% RH) and Fusarium roseum, Fusarium oxysporum only at 96% RH level. The relative humidity level lower than 62%, i.e. at 52% level exhibited no fungal growth on sandstone surface during two-year observations. During the study pattern it was noticed that diversity decreased gradually and dominance of particular species increased with the time factor. Analysis of sandstone after fungal colonization by X-ray diffraction and SEM showed the formation of newly formed biomineral.     

Particulate forms of radium and barium in uranium mine waste waters and receiving river waters

A method of selective dissolution was used for analysis of particulate forms of radium and barium in a system consisting of uranium mine waste waters purified by coprecipitation with barium sulphate and of adjacent river waters. Four particulate forms of both the elements were distinguished: “loosely bound”, “acid soluble”, Ba(Ra)SO₄ and “in crystalline detritus”. It was found that the distribution of radium and barium between dissolved and particulate forms in waste waters depended on the time interval elapsing between the sampling and membrane filtration of the waters. No such dependence occurred in river water. The main particulate form of radium and barium in the system was Ba(Ra)SO₄. River water upstream of the mine water discharge contained radium mainly in “acid soluble” form or “in crystalline detritus” and barium as BaSO₄ or “crystalline detritus”. In unpurified mine effluents, a large part of radium and barium was present as “crystalline detritus”. Abundance of the “loosely bound” form was very low in all the samples analyzed. The bond of radium in bottom sediments was approximately the same as that in the solids suspended in waste waters. Suitability and accuracy of the selective dissolution method for analysis of surface and waste waters has been demonstrated by the analysis of the results and by radiotracer experiments.     

Partitioning of copper onto suspended particulate matter in river waters

Suspended particles and river water from the Susquehanna River, White Clay Creek and the Delaware River were collected to experimentally study the partitioning of copper. The effects of many factors that may influence the partitioning coefficient (Kd) including pH, total suspended solids (TSS), total copper concentration ([Cu]T), dissolved organic matter (DOM), particulate organic matter (POM), hardness, and ionic strength were investigated by performing batch adsorption experiments. The results implied that organic matter binding sites in both the aqueous and solid phases play the most important role in controlling copper partitioning. Other major factors governing the partitioning are pH and TSS. Kd increases with pH in the pH range 3-8. TSS increases caused decreases in Kd values, which may be attributed to the decrease in the quantity of available binding sites caused by interparticle interactions, rather than by the redistribution of organic matter between solid and solution phases with the variation of TSS. Kd decreases slightly when total Cu concentration increases; however, Kd can be considered to be independent of Cu concentration when TSS is high. The effects of calcium competition and ionic strength on partitioning are small.     

Acid-stimulated phosphate uptake by activated sludge microorganisms under aerobic laboratory conditions

Activated sludge inocula taken from five different wastewater treatment plants were grown aerobically under laboratory conditions on mineral salts medium containing either glucose or skimmed milk powder as carbon source. Cultures showed increases of between 50% and 143% in levels of phosphate uptake from the medium when the growth pH was 5.5 rather than 7.5. Of 100 individual sludge microbial isolates studied, 34 demonstrated such acid-stimulated luxury phosphate uptake; the optimum pH for the process was shown to lie between 5.0 and 6.5. Enhanced phosphate removal by these isolates was accompanied by increases of between 2 and 10.5-fold in their polyphosphate content; this was visualised as intracellular inclusions. Acid-stimulated luxury phosphate uptake by environmental microorganisms is a previously-unrecognised phenomenon that may have application in novel technologies for nutrient removal from wastewaters.     

Determination of smoldering time and thermal characteristics of firebrands under laboratory conditions

The laboratory experiment was conducted to simulate the transfer of smouldering particles produced in forest wildfires by a heated gas flow. The pine bark pieces with the linear dimensions L=(15; 20; 30) mm and a thickness of h=(4−5) mm were selected as model particles. The rate and temperature of the incident flow varied in the range of 1–3 m/s and 80–85 °C, respectively. The temperature of the samples was recorded using a thermal imager. To determine the minimum smouldering temperature of pine bark, the thermal analysis was conducted. The minimum smouldering temperature of pine bark was found to be 190 °C. This temperature will cause thermal decomposition of bark only at the first stage (oxidation of resinous components). In the study the smouldering time, the temperature and the weight of samples were obtained and analyzed under various experimental conditions. The data analysis shows that the increase in the particle size leads to the decrease in their mass loss, and the rate change of the incident flow does not practically influence the mass change. For particles with the linear dimensions of 10 mm and 20 mm, the mass varies from 6% to 25%. The maximum mass loss is observed for the flows with a rate of 1 and 2 m/s. The results have shown that the increase in the particle size leads to the increase in the smouldering time. The position of the particle plays an important role, the effect of which increases with increasing the particle size. The calculations showed that the smouldering time of bark samples is long enough for the particles to serve as new sources of spot fires. The particles were found to be transported to a distance of 218 m from the fire line which can certainly influence the propagation of the fire front.     

Mutagenic potential of laboratory chlorinated river water

Sample water was taken from a river and chlorinated at a concentration of 5 mg 1(-1) chlorine for 20 h in the laboratory in order to examine the effect of chlorination on the mutagenic potential of organic extracts that were recovered using XAD-2 resin and diethyl ether. It was found that the XAD extracts recovered from the river water showed per se strong mutagenic activity, in the presence of S-9 mix, towards Salmonella typhimurium TA 1538. When the mutagenic activity of the XAD extracts was related to the initial water volume, chlorination increased both the direct-acting and the S-9 dependent mutagenic activity. This suggests that chlorination produced de novo direct-acting and S-9 dependent mutagens and/or increased pre-existing mutagenic activities. In addition, in this study XAD extracts recovered from chlorinated and unchlorinated river water were divided into a neutral, basic and acidic fraction respectively. When the mutagenic activity of each fraction was related to the initial water volume, the neutral fraction showed the most marked increase in mutagenic activity with, and without, the S-9 mix in the chlorinated river water.     

Arsenic speciation in river and estuarine waters from southwest Spain

An arsenic speciation survey was carried out in water samples from the Tinto and Odiel Rivers (southwest of Spain), as well as their common estuary. Both rivers are affected by acid mine drainage (AMD) and represent an input of heavy metals into the estuary, which also suffers from industrial water discharges. Samples were taken in December 2000 and July 2001. The arsenic species considered were arsenite (As(III)), arsenate (As(V)), monomethylarsonic (MMA) and dimethylarsinic (DMA) ions using coupled high-performance liquid chromatography-hydride generation-inductively coupled plasma-mass spectrometry (HPLC-HG-ICP-MS) for their determination. Parameters such as pH, salinity, redox potential and dissolved O2 were also measured. The results revealed that the acid mine drainage originating mainly during winter along the upper part of the Tinto River course causes high inorganic concentrations of dissolved arsenic, up to 600 microg l(-1) of As(III) and 200 microg l(-1) of As(V). In summer, As(III) levels decreased due to the diminution of the input from acid mine drainage and also because of oxidation, with a corresponding increase of As(V) level. Furthermore, the extreme acidic conditions of this river (pH 2.3-2-6) do not allow biological activity sufficient to produce significant concentrations of methylated arsenic species. The arsenic concentrations in the nearby Odiel River were always 5-10 times lower than in the Tinto River, with arsenic levels usually below 100 microg l(-1), dominated by As(V), indicating that it is less affected by acid mine drainage. The highest inorganic arsenic species concentrations were found where the river crosses a mining site, which corresponds to the highest As(III) values. Significant biological activity in this river produced methylated species that were detected along the water-course, with the highest concentrations at the lower course of the river, accounting for up to 53-61% of the total dissolved arsenic. At the common estuary formed by both rivers, only arsenate was detected in most samples at lower concentrations than in the riverine water samples. The tidal cycle showed a similar pattern of dilution of the arsenate when seawater comes into the estuary. Methylated species were not found either in summer or winter, at least at the 0.1 microg l(-1) level, possibly because of the high turbidity of the waters, producing an inhibition of the phytoplankton activity. In addition to the riverine inputs into the common estuary, industrial activity also represents an important source of arsenic as the discharge from a Cu smelter produced the highest arsenate level of all samples in estuary and also the only sample with significant arsenite concentration. Furthermore, the underlying iron-oxide-rich sediments represent an importance source of arsenic into the water column. In three nearby estuaries not affected by industrial activity or acid mine drainage, arsenic levels remained below detection limits.