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1.

Recently, the European Food Safety Authority (EFSA) has banned the use of iprodione (IPR), a common hydantoin fungicide and nematicide that was frequently used for the protective treatment of crops and vegetables. In the present study, the treatment of 2 mg/L (6.06 μM) aqueous IPR solution through ultraviolet-C (UV-C)-activated persulfate (PS) advanced oxidation process (UV-C/PS) was investigated. Baseline experiments conducted in distilled water (DW) indicated that complete IPR removal was achieved in 20 min with UV-C/PS treatment at an initial PS concentration of 0.03 mM at pH?=?6.2. IPR degradation was accompanied with rapid dechlorination (followed as Cl? release) and PS consumption. UV-C/PS treatment was also effective in IPR mineralization; 78% dissolved organic carbon (DOC) was removed after 120-min UV-C/PS treatment (PS?=?0.30 mM) compared with UV-C at 0.5 W/L photolysis where no DOC removal occurred. LC analysis confirmed the formation of dichloroaniline, hydroquinone, and acetic and formic acids as the major aromatic and aliphatic degradation products of IPR during UV-C/PS treatment whereas only dichloroaniline was observed for UV-C photolysis under the same reaction conditions. IPR was also subjected to UV-C/PS treatment in simulated tertiary treated urban wastewater (SWW) to examine its oxidation performance and ecotoxicological behavior in a more complex aquatic environment. In SWW, IPR and DOC removal rates were inhibited and PS consumption rates decreased. The originally low acute toxicity (9% relative inhibition towards the photobacterium Vibrio fischeri) decreased to practically non-detectable levels (4%) during UV-C/PS treatment of IPR in SWW.

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2.
The interaction of natural organic matter with phytoplankton communities in freshwater ecosystems is an intensively studied subject matter. Previous studies showed that apparently plant-derived phenols were able to inhibit algal and cyanobacterial growth. Furthermore, it was also assumed that humic substances (HS), which comprise the major part of dissolved organic carbon in freshwater ecosystems, directly interact with freshwater phototrophs. For example, quinoid building blocks of HS were thought to be algicidal. To identify key environmental variable for the toxic action of potential quinone algicides, we tested the toxicity of hydroquinone (HQ) to different eukaryotic and prokaryotic freshwater phototrophs in terms of growth performance and investigated also the effect of HQ oxidation at different pH values on its algicidal potential. It was shown that cyanobacterial species were much more susceptible to hydroquinone than coccal green algal species were, with Microcystis aeruginosa being the most sensitive species by far. In addition, it was obvious that the aging of hydroquinone-stock solution at pH 11 led to polymerization and, by this process, to a total loss of toxicity; whereas the algicidal potential sustained if the polyphenol was kept at pH 7. Since most lakes with heavy blooms of phototrophs possess pH values clearly above 7.0, it is questionable, if polyphenols in general and quinones in particular are the effective chemicals and if litter and straw leachates are applied as means to combat algal and cyanobacterial blooms.  相似文献   

3.
Bioavailability of dissolved organic nitrogen in treated effluents.   总被引:2,自引:0,他引:2  
The research objective was to assess dissolved organic nitrogen (DON) bioavailability in wastewater effluents from a pilot-scale nitrification plant and a laboratory-scale total nitrogen (TN) removal plant. The DON bioavailability was assessed using a 14-day bioassay protocol containing bacterial and algal inocula. Nitrogen species, dissolved organic carbon, chlorophyll a, and biomass (as total suspended solids and culturable cell counts) concentrations were measured to assess DON bioavailability. The results showed an increase in algal chlorophyll a concentration, with a concurrent increase in algal biomass over time; increased bacterial counts and a decrease in DON concentration over time; and increased carbon-to-nitrogen ratio at the end of the 14-day bioassay, indicating effluent DON bioavailability to algae and bacteria. Approximately 18 to 61% of the initial DON in low-total-nitrogen wastewater effluent (TN = 4 to 5 mg/L) sample was bioavailable. The results show that bacteria and algae uptake and release DON during their growth.  相似文献   

4.
Wastewater nutrient removal by Chlorella pyrenoidosa and Scenedesmus sp   总被引:4,自引:0,他引:4  
Two different species of photosynthetic microalgae, Chlorella pyrenoidosa and Scenedesmus sp., were grown in settled and activated sewage filtrates at two different inoculum sizes, aimed to reduce nutrient load from wastewater. Higher growth rates were recorded in cultures with higher inoculum size, and algal cells usually grew better in settled sewage than in activated sewage. As algae started to grow and multiply, both nitrogen and phosphorus content in wastewater decreased significantly. The removal rate was rapid during the first week of growth and more than 2/3 of wastewater N and P was reduced. After the initial period, the removal rate slowed down. At the end of this study, more than 80% of total-P and inorganic N present in settled sewage were reduced but such removal efficiency was lower in activated sewage. In general, high inoculum size of algal cells provided more N and P removal than low inoculum, and Chlorella cells performed better than Scenedesmus. These results suggest that cultivation of Chlorella seems to be one of the feasible methods to reduce the amount of nitrogen and phosphorus entering the nearby coastal water, thus preventing the eutrophication problem. It is also clear that algal ponds with high inoculum size might be more suitable to be installed as a secondary rather than a tertiary treatment process.  相似文献   

5.
The performance of various algal indices to document improvements in water quality across a low nutrient concentration gradient was assessed during 2 years in the St Lawrence River (Quebec, Canada). Water-quality variables and periphyton samples were collected on navigational buoys near Montreal during the spring, summer and fall of 1994 and 1995. Exposure to urban wastewater varied widely within the sector surrounding the island of Montreal, with some areas upstream receiving no direct effluents and areas further downstream receiving treated and untreated wastewater. Faecal coliform concentrations provided a good tracer of effluents and were significantly correlated to nutrient concentrations (r = 0.33-0.72, p < 0.001) and water transparency (r = 0.70, p < 0.001). Despite a strong gradient in faecal coliform concentration (< 2 to > 20 000 UFC/100 ml), algal biomass and diversity did not reflect differences between sites with varying levels of urban wastewater. Taxonomic composition of periphyton communities, particularly the presence of the cyanophyte Plectonema notatum Schmidle, was related (r = 0.48, p = 0.004) to exposure to urban effluents. Variables describing seasonal changes (temperature, Julian day, river discharge, conductivity, NO2-NO3) explained a large fraction of total variance (38-52% of total variance) and thus exerted the predominant influence on algal biomass and species composition in the St Lawrence River. Variables describing the presence of effluents explained 1-22% of the variance in compositional data. Subtle changes in periphyton species composition were the only response to different levels of exposure to urban wastewater in the Montreal area, which represented relatively small differences in comparison to natural seasonal variability.  相似文献   

6.
高效菌藻塘系统对农村污水中磷的强化去除效果研究   总被引:1,自引:1,他引:0  
研究了高效菌藻塘系统处理太湖地区农村生活污水除磷效果及其强化措施。高效菌藻塘和水生生物塘HRT分别为8 d和4 d,进水总磷浓度为1.7~17.1 mg/L,出水总磷浓度全年平均值为3.33 mg/L,高效菌藻塘系统的除磷能力欠佳。通过降低水生生物塘内水深、采用废弃石膏作为填料构建了新型复合水生生物塘,HRT=1.6 d条件下,复合水生生物塘出水总磷可保持在1 mg/L以下,可达到GB18918-2002一级B排放标准。  相似文献   

7.
A unicellular green microalga, Chlorella vulgaris, entrapped in calcium alginate as algal beads were employed to remove nutrients (N and P) from simulated settled domestic wastewater. A significantly higher nutrient reduction was found in bioreactors containing algal beads (at concentrations ranging from 4 to 20 beads ml(-1) wastewater) than the blank alginate beads (without algae). A complete removal of NH(4)(+)-N and around 95% reduction of PO(4)(3-)-P was achieved within 24 h of treatment in bioreactors having the optimal algal bead concentration (12 beads ml(-1), equivalent to 1:3 algal beads:wastewater, v/v). The NH(4)(+)-N removal was significantly lower at low (around 4 beads ml(-1)) and high (>15 beads ml(-1)) algal bead concentrations. On the other hand, the effect of bead concentration on phosphate removal was less obvious, and bead concentrations ranging from 8 to 20 beads ml(-1) showed comparable percentages of phosphate reduction. Algal uptake and adsorption on alginate gels were found to be the major processes involved in the removal of N and phosphate in the present study. In addition, NH(4)(+)-N could be lost via ammonia volatilization while PO(4)(3-)-P was removed by chemical precipitation, as alkaline pH was recorded in the immobilized microalgal treatment system.  相似文献   

8.
The microscopic green alga, Chlorella pyrenoidosa was grown in settled and activated sewage under two different culture systems, batch and semi-continuous. Good growth was obtained in both types of wastewater and the algal production was comparable to and even higher than that found in commercial Bristol medium. The semi-continuous culture supported more growth than the batch system. There was a close relationship between algal growth and the amount of nutrient removed from both settled and activated sewage. A more rapid drop in NH(4)(+)-N was found in settle rather than activated sewage. The NH(4)(+)-N of settled sewage dropped from its initial 27 to 5 mg litre(-1) in both culture systems. On the other hand, the NO(3)(-)-N of activated sewage started to decrease from Day 2 onwards and the final NO(3)(-)-N concentration was less than 1 mg litre(-1) (over 90% removal efficiency). The amount of total inorganic nitrogen being reduced due to algal culture was similar in both types of sewage. The changes of phosphate content followed the same trend in both sewage, the P concentration increased slightly in the first two days then decreased, especially in the semi-continuous cultures. The final ortho-P in the sewage treated by Chlorella in semi-continuous culture was less than 5 mg litre(-1) (about 62% reduction). Such removal efficiency was slightly lower than those reported in previous studies. In general, the semi-continuous algal culture appeared to be a more suitable and efficient way for wastewater treatment than the batch system. With respect to the total reduction of wastewater inorganic N and P by means of Chlorella cells, there was no significant difference between settled and activated sewage.  相似文献   

9.
Environmental Science and Pollution Research - This study evaluated the responses of a mixed culture of two cyanobacterial species (Microcystis aeruginosa and Synechocystis sp.) and two eukaryotic...  相似文献   

10.
Dissolved organic matter (DOM) has been shown to affect phytoplankton species directly. These interactions largely depend on the origin and molecular size of DOM and are different in prokaryotes and eukaryotes. In a preceding study, however, two humic substance preparations did not adversely affect coccal green algae or cyanobacterial growth even at high concentrations of dissolved organic carbon (DOC). These results contradicted previous findings, showing a clear, negative response of different phototrophs to much lower DOC concentrations. To test whether or not at least defined building blocks of humic substances (HSs) are effective algicidal structures, we enriched two humic preparations with hydroquinone and p-benzoquinone, respectively, and exposed two different green algae, Pseudokirchneriella subcapitata and Monoraphidium braunii, and two cyanobacterial species, Synechocystis sp. and Microcystis aeruginosa, to the unmodified and enriched HSs. As response variables, growth rates in terms of biomass increase, chlorophyll-a content, and photosynthetic yield were measured. The highest concentration (4.17 mM DOC) of the modified HSs clearly inhibited growth; the cyanobacterial species were much more sensitive than the green algal species. However, realistic ecological concentrations did not adversely affect growth. Aerating the exposure solution for 24 h strongly reduced the inhibitory effect of the modified HSs. The algicidal effect was obviously caused by monomers and not by polymerised high molecular weight HSs themselves. Furthermore, the maximum quantum yield (Φ PSII max) was stimulated in the green algal species by low and medium DOC concentrations, but reduced in the cyanobacterial species upon exposure to higher HS concentrations. The quinone- and phenol-enriched HSs only showed algicidal activity at high concentrations of 4.17 mM DOC and lost their effects over time, presumably by oxidation and subsequent polymerisation. This study confirms that the applied humic substances themselves are not effective algicides even if enriched in effective structures.  相似文献   

11.
Wen CG  Chen TH  Hsu FH  Lu CH  Lin JB  Chang CH  Chang SP  Lee CS 《Chemosphere》2007,67(8):1588-1600
The objectives of this paper are to determine effects of different grass species and their harvests on pollutant removal, elucidate impacts on soil characteristics and grass constituents, observe grass yield and quantify nutrient uptake by vegetation in an overland flow system (OLFS). Polluted creek water was applied to eight channels in the OLFS, which were planted with Paragrass, Nilegrass, Cattail, and Vetiver, with each two channels being randomly planted with a given grass species. The grass in one channel was harvested while that in the other channel was not. At a high rate of 27.8 m d(-1) hydraulic loading, the removal efficiencies of conventional pollutants such as BOD, COD, suspended solids (SS), and total coliforms in wastewater are not affected by the type of the grasses species, but those of nitrogen and phosphorus are affected by different species. Overall average removal efficiencies of BOD, COD, SS, ammonia, total nitrogen, total phosphorus and total coliforms through the OLFS are 42%, 48%, 78%, 47%, 40%, 33% and 89%, respectively. The concentration of nitrate, however, increases due to nitrification. Soil characteristics in OLFS have been changed significantly; specific conductivity, organic matter, exchangeable magnesium, extractable copper and zinc in soils all increase with time while pHs decrease. During the winter season, there is a significant accumulation of nitrate in grass with the subsequent reduction during the active growing season (Spring). The contents of nitrate and phosphorus in grass tissue are higher than those of grass in general pastureland, probably due to nutrient luxury uptake by grass. The overall grass yield, growth rate and nutrient uptake are quantified and implication of such high rate OLFS discussed.  相似文献   

12.
以养猪场废水作为研究对象,采用序列间歇式活性污泥法SBR,通过实验研究了供气量、pH、排泥量、原水稀释倍数、水力停留时间(HRT)对SBR出水水质的影响。结果表明,供气量为375 L/(min·m3)、pH为8.0,并添加排泥100 mL的操作,可使SBR处理效果明显提高,COD、磷和凯氏氮去除率最高分别可达96.37%、94.14%、99.38%。逐步降低进水稀释倍数有利于培养出处理高浓度有机养猪废水的活性污泥,可将平均COD、磷和凯氏氮含量高达9 161.24、33.41和1 502.77 mg/L的养猪废水处理至出水的490.11、5.35和17.84 mg/L。降低HRT对SBR去除率影响不大。  相似文献   

13.
In this study, a three-factor, three-level Box-Behnken design with response surface methodology were used to maximize the TOC removal and minimize the H2O2 residual in the effluent of the combined UV-C/H2O2-VUV system for the treatment of an actual slaughterhouse wastewater (SWW) collected from one of the meat processing plants in Ontario, Canada. The irradiation time and the initial concentrations of total organic carbon (TOCo) and hydrogen peroxide (H2O2o) were the three predictors, as independent variables, studied in the design of experiments. The multiple response approach was used to obtain desirability response surfaces at the optimum factor settings. Subsequently, the optimum conditions to achieve the maximum percentage TOC removal of 46.19% and minimum H2O2 residual of 1.05% were TOCo of 213 mg L?1, H2O2o of 450 mg L?1, and irradiation time of 9 min. The attained optimal operating conditions were validated with a complementary test. Consequently, the TOC removal of 45.68% and H2O2 residual of 1.03% were achieved experimentally, confirming the statistical model reliability. Three individual processes, VUV alone, VUV/H2O2, and UV-C/H2O2, were also evaluated to compare their performance for the treatment of the actual SWW using the optimum parameters obtained in combined UV-C/H2O2-VUV processes. Results confirmed that an adequate combination of the UV-C/H2O2-VUV processes is essential for an optimized TOC removal and H2O2 residual. Finally, respirometry analyses were also performed to evaluate the biodegradability of the SWW and the BOD removal efficiency of the combined UV-C/H2O2-VUV processes.  相似文献   

14.
Abstract

The Henry’s law constant is important in the gas-liquid mass transfer process. Apparent dimensionless Henry’s law constant, or the gas-liquid partition coefficient (K’ H), for both hydrophilic (methanol, isopropyl alcohol, and acetone) and hydrophobic (toluene and p-xylene) organic compounds in deionized (DI) water, a wastewater with a maximum total dissolved organic carbon (DOC) content of 700 mg/L, and DI water mixed with a maximum activated sludge suspended solid (SS) concentration of 40,000 mg/L were measured using the single equilibrium technique at 293 K.

Experimental results demonstrate that the K’ H of any of the test volatile organic compounds varied among three situations. First, the KH of the hydrophilic compounds in mixed liquor with the maximum SS concentration was 9–21% higher than those in DI water. Second, those for toluene and p-xylene were 77% and 93% lower, respectively, in the mixed liquor with the maximum SS concentration. Third, the KH values of all of the test compounds in the wastewater were only 10% lower than those in DI water.

A model was developed to relate K’ H with wastewater DOC and the SS concentration in the activated sludge using an organic carbon-water partition coefficient and activated sludge-water partition coefficient as model parameters. The model was verified and model parameters for test compounds estimated.  相似文献   

15.
Abstract

The effects of wastewater from olive processing on seed germination and early plant growth of different vegetable species were examined. Three types of wastewater at different concentrations were tested: raw wastewater, wastewater with organic matter removed and deionized wastewater.

Results generally indicate an inhibitory effect on seed germination and early plant growth by all treatments containing any kind of wastewater. Of the three types of effluent, raw wastewater had the greatest depressive effect, followed by deionized wastewater and finally effluent with organic matter removed. Barley showed the least sensitivity to phytotoxic effects while tomato was the plant most affected. The remaining vegetable species showed an intermediate sensitivity.  相似文献   

16.
Zhang Z  Rengel Z  Meney K 《Chemosphere》2008,72(11):1823-1828
The concentrations of nutrients (N and P) in the wastewater and loading rate to the constructed wetlands may influence the nutrient removal from the secondary-treated municipal wastewater using wetland plants. Three loading rates of N (low 5.7, medium 34.3 and high 103 mg N d(-1)) and two of P (low 3.4 and high 17.1 mg P d(-1)) were studied in simulated secondary-treated municipal wastewater using Schoenoplectus validus (Vahl) A. L?ve & D. L?ve in the vertical free surface-flow wetland microcosms. After 70-d growth, there were significant interactive effects of N and P on the total, above-ground and root biomass. The below-ground biomass (rhizome and root) was negatively affected by the high N treatment. The tissue concentrations of N increased with an increase in N additions and decreased with an increase in P applications, whereas the tissue concentrations of P increased with an increase in P additions and decreased with an increase in N applications at the low P treatment, but increased at the high P treatment. Significant interactive effects of N and P loadings were found for the removal efficiencies of NH(4) and P, but not that of NO(x). The plant uptake, substrate storage and other losses (e.g. denitrification and formation of organic film) had similar contribution to N removal when N loading was relatively low. The P storage by substrate was the main contribution to P removal when P loading was high, but plant uptake was the major factor responsible for P removal when P loading was low and N loading was high. The high nutrient availability and optimum ratio of N:P are required to stimulate growth of S. validus, resulting in preferential allocation of resources to the above-ground tissues and enhancing the nutrient removal efficiencies, but the high N concentration in wastewater may hamper the growth of S. validus in constructed wetlands.  相似文献   

17.
Abstract

Nitrogen transformations and their effect on aerobic suspended growth treatment of an industrial wastewater were studied in three parallel bench-scale reactors operated at 5 "C at mean cell residence times (MCRT) of 15, 30, and 60 days. In normal process wastewater, the bulk of influent nitrogen was in organic form, and the fraction transformed was almost totally incorporated into synthesized biomass. Assimilative control by heterotrophs maintained ammonianitrogen levels below permitted effluent levels, and nitrification was not significant. Although volatile suspended solids had a nitrogen content of only 5% to 8%, effective organics removal was maintained, and total organic carbon and filtered daily average five-day biochemical oxygen demand (BODS) were below permitted effluent levels. A marked improvement in settleability and lower effluent total suspended solids was achieved by adding ammonia-nitrogen to the wastewater in excess of stoichiometric growth requirements.

During a batch production cycle of a cationic chemical, the ratio of nitrogen to chemical oxygen demand and the fraction of the total influent nitrogen in soluble form increased in the wastewater. Reactor effluent ammonia levels increased to above permit levels at all three MCRTs during treatment of wastewater containing cationic production effluents. The magnitude of ammonia increase was greater for longer MCRTs, suggesting that synthesis of cell mass was not capable of assimilating the increased ammonia supply under these non-steady conditions. The experimental results suggest several potential strategies for operating the aerobic process at the treatment facility, including adding nitrogen to improve settleability and discontinuing these additions when wastewater contains a high ratio of nitrogen to chemical oxygen demand and an elevated soluble nitrogen fraction  相似文献   

18.
Pollutant-removal efficiency of certain macrophytes and algae, such as Eichhornia crassipes, Microcystis aeruginosa, Scenedesmus falcatus, Chlorella vulgaris and Chlamydomonas mirabilis, has been tested in laboratory conditions to evaluate their potential role in wastewater treatment. Sewage of Varanasi city, mixed with the effluents of about 1200 small-scale industries, was used for the tests. The investigation was performed in three stages i.e. a water hyacinth culture followed by an algal culture, and finally a second water hyacinth culture. For the first water hyacinth culture, 10 water hyacinth plants were grown in a tank of wastewater with 15 days' retention time. In the second stage, algal species were cultured in the treated wastewater for 5 days, whilst in the third stage, water hyacinth plants were again grown for further treatment of the wastewater for 9 days. This three-stage aquaculture resulted in very high reductions of BOD (96.9%), suspended solids (78.1%), total alkalinity (74.6%), PO(4)-P (89.2%), NO(3)-N (81.7%), acidity (73.3%), NH(4)-N (95.1%), COD (77.9%), hardness (68.6%) and coliform bacteria (99.2%). An increase in the concentration of dissolved oxygen (70%) was also observed.  相似文献   

19.
The present study used an eco-ditch system that employed Eichhornia crassipes, Bacillus subtilis, and Bellamya aeruginosa (E–B–B) during the summer and fall (high temperature) seasons and a second eco-ditch system that employed Elodea nuttallii, a compound microbial preparation called “EM bacteria”, and Hypophthalmichthys molitrix (E–E–H) during the winter and spring (low temperature) seasons successively to purify the discharged wastewater produced by Chinese soft-shelled turtle greenhouse cultivation. The wastewater was sampled, and the dynamic changes in the major nutrient pollutant indicators over several months were analysed. After the E–B–B and E–E–H eco-ditch purification systems were operated for nearly 140 days each, the following results were observed: the total nitrogen (TN) removal rates in the wastewater were 75 % and 69 %, respectively; the total phosphorus (TP) removal rates were 82 % and 86 %, respectively; the NH4 +-N removal rates were 91 % and 75 %, respectively; the chemical oxygen demand (CODcr) decreased 54 % and 44 %, respectively; the dissolved oxygen (DO) contents increased nearly 3 to 4 times; and the wastewater was maintained at neutral or alkaline pH values. The wastewater physical traits gradually changed from being yellow, brown, and muddy to being pale yellow, slightly turbid, and odourless. Both eco-ditch systems were observed to have a relatively favourable effect on the purification of Chinese soft-shelled turtle aquaculture wastewater. The continuous use of both eco-ditch systems could result in a year-round purification effect on Chinese soft-shelled turtle greenhouse aquaculture wastewater; therefore, this method has good prospects for promotion and application.  相似文献   

20.

Diversity and rapidly multiplication of the pollutants incite as to improve the conventional treatments wastewater methods. One of the bottlenecks often faced is the presence into wastewater of organic pollutants with complex structures that requests the design of efficient processes. Thus, this work investigates the removal of polyvinylamine sulfonate anthrapyridone (PSA) dye which complex structure makes difficult its degradation by conventional technologies. For that, a heterogeneous oxidative process using pyrite as sustainable catalyst was designed. Initially, the performance of the system BBD-carbon felt as anode and cathode, respectively for the production of H2O2 was determined in comparison with system boron-doped diamond nickel foam. The carbon felt electrode provided the highest oxidant production, and it was selected for the treatment of the polymeric dye. Several oxidative processes were evaluated, and the best degradation levels were obtained by application of electro-Fenton-pyrite process. In addition, it was determined that dye removal followed a kinetic model of pseudo-first-order achieving the highest efficiency by operation at optimum dosage of pyrite 2 g/L and 200 mA of current intensity. Depending on the optimal experimental conditions, these values lead to a nearly complete mineralization (total organic carbon removal of 95%) after 6 h. Furthermore, the reusability of pyrite was evaluated, by removal of PSA in four cycles.

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