Coagulation and precipitation as post-treatment of anaerobically treated primary municipal wastewater.

The main objective of this study was to investigate the feasibility of coagulation as a post-treatment method of anaerobically treated primary municipal wastewater. Both mesophilic and ambient (20 degrees C) temperature conditions were investigated in a laboratory-scale upflow anaerobic sludge bed (UASB) reactor. In addition, optimization of the coagulant, both in terms of type and dose, was performed. Finally, phosphorus removal by means of aluminum and iron coagulation and phosphorus and ammonia nitrogen removal by means of struvite precipitation were studied. Anaerobic treatment of primary effluent at low hydraulic retention times (less than 15 hours) resulted in mean chemical oxygen demand (COD) removals ranging from 50 to 70%, while, based on the filtered treated effluent, the mean removals increased to 65 to 80%. Alum coagulation of the UASB effluent gave suspended solids removals ranging from approximately 35 to 65%. Turbidity removal reached up to 80%. Remaining COD values after coagulation and settling were below 100 mg/L, while remaining total organic carbon (TOC) levels were below 50 mg/L. Filterable COD levels were generally below 60 mg/L, while filterable TOC levels were below 40 mg/L. All coagulants tested, including prepolymerized aluminum and iron coagulants, demonstrated similar efficiency compared with alum for the removal of suspended solids, COD, and TOC. Regarding struvite precipitation, optimal conditions for phosphorus and nitrogen removal were pH 10 and molar ratio of magnesium: ammonia-nitrogen: phosphate-phosphorus close to the stoichiometric ratio (1:1:1). During struvite precipitation, removal of suspended solids reached 40%, while turbidity removal reached values up to 80%. The removal of COD was approximately 30 to 35%; yet, when removal of organic matter was based on the treated filterable COD, the removal increased to approximately 65%. In addition, nitrogen was removed by approximately 70%, while phosphorus removal ranged between approximately 30 and 45% on the basis of the initial phosphorus concentration. Finally, size fractionation of the organic matter (COD) showed that the various treatment methods were capable of removing different fractions of the organic matter.     

Treatment of landfill leachate by electrochemical oxidation and anaerobic process.

The removal performance of typical refractory organic compounds in landfill leachate was investigated during the electrochemical (EC) oxidation and anaerobic process combined treatment system in this paper. The results indicated that the treatment of landfill leachate by the combined system was highly effective. The toxicity of leachate was notably decreased after the electrochemical oxidation process and the biodegradability was improved. The concentration of the organic acid with low molecular weight in the leachate increased from 28% to 90% based on the biodegradability assays after the EC oxidation process. The anaerobic digestion could further remove the residual organic compounds. At a hydraulic retention time (HRT) of 16 hours and an organic loading rate (OLR) of 8 kg COD/m3 d, the concentration of COD, SS, ALK, VA, N-TKN, N-NH4+ and P-PO4(3)- [corrected] in UASB effluent were 532, 12, 6744, 400, 540, 455 and 11.6 mg/L, respectively, with approximately 90% removal efficiency of COD. The organic compounds in the landfill leachate revealed different degradation characteristics in the combined system. p-chloroaniline, bisphenol A, 6-methyl-2-phenyl-quinoline, dimethylnaphthaline and N'-(2-methyl-4-chlorophenyl)-N-cyclohexyformamidine, classified into the first group in this paper, were completely removed by the EC oxidation and did not reappear in the effluent of the UASB reactor. Phenylacetic acid, 3-methyl-indole and N-cyclohexyl-acetamide, called the second group, were completely removed, but reappeared in the UASB reactor. 4-methyl-phenol, 3,4-dihydroisoquinoline, 2(3H)-benzothiazolone, exo-2-hydroxycineole and benzothiazole, the third group, were degraded little in the EC oxidation process, but extensively removed by the anaerobic process. Benzoic acid, benzenepropanoic acid and 2-cyano-3,5-dimethyl-1-hydroxypyrrole, the fourth group, concentration obviously increased in the EC process, but was completely removed in the UASB reactor. The content of volatile fatty acids (VFAs) markedly increased from 0.68% in the leachate to 16.18% in the effluent from the electrochemical oxidation process (EC(effl)). In addition, the degradation rate of organic compounds from the landfill leachate was different in the EC oxidation and anaerobic process.     

EGSB反应器处理城市生活垃圾沥滤液

采用膨胀颗粒污泥床(EGSB)反应器对城市生活垃圾焚烧厂产生的垃圾沥滤液进行处理。实验结果表明:中温条件下,当COD浓度为55 000 mg/L左右,有机容积负荷(OLR)为22.8 kg COD/(m3.d)时,EGSB对垃圾沥滤液具有较好的的处理效果,COD去除率可达94.2%。当进水COD为72 000 mg/L左右时,为保证反应器的稳定运行,OLR应降低至18.2 kg COD/(m3.d),此时COD去除率可以达到88%左右,出水COD平均为9 103 mg/L。垃圾沥滤液和EGSB处理出水均以小分子量有机物为主,其中<4 kDa的有机物分别占76.5%和74.4%。EGSB对整个分子量区间的溶解性有机物都有较好的处理效果,其中对大分子有机物的处理效率相对更高。     

Transformation of effluent organic matter during subsurface wetland treatment in the Sonoran Desert

The fate of dissolved organic matter (DOM) during subsurface wetland treatment of wastewater effluent in a hot, semi-arid environment was examined. The study objectives were to (1) discern changes in the character of dissolved organics as consequence of wetland treatment (2) establish the nature of wetland-derived organic matter, and (3) investigate the impact of wetland treatment on the formation potential of trihalomethanes (THMs). Subsurface wetland treatment produced little change in DOM polarity (hydrophobic-hydrophilic) distribution. Biodegradation of labile effluent organic matter (EfOM) and internal loading of wetland-derived natural organic matter (NOM) together produced only minor changes in the distribution of carbon moieties in hydrophobic acid (HPO-A) and transphilic acid (TPI-A) isolates of wetland effluent. Aliphatic carbon decreased as a percentage of total carbon during wetland treatment. The ratio of atomic C:N in wetland-derived NOM suggests that its character is determined by microbial activity. Formation of THMs upon chlorination of HPO-A and TPI-A isolates increased as a consequence of wetland treatment. Wetland-derived NOM was more reactive in forming THMs and less biodegradable than EfOM. For both HPO-A and TPI-A fractions, relationships between biodegradability and THM formation potential were similar among EfOM and NOM isolates; the less biodegradable isolates exhibited greater THM formation potential.     

Effectiveness of electrocoagulation process in removing organic compounds from slaughterhouse wastewater using monopolar and bipolar electrolytic cells

Slaughterhouse wastewaters contain varied and high amounts of organic matter (e.g., proteins, blood, fat). In order to produce an effluent suitable for stream discharge, electrochemical techniques have been particularly explored at the laboratory pilot scale for organic compounds removal from poultry slaughterhouse (PS) effluent. Electrocoagulation (EC) process was tested using either mild steel or aluminium electrodes arranged in bipolar (BP) or monopolar configuration system. Results showed that the best performance was obtained using mild steel BP electrode system operated at a current intensity of 0.3A, through 60 or 90 min of treatment. Under these conditions, removals of 86+/-1% and 99+/-1% were measured for BOD and oil and grease, respectively, whereas soluble COD and total COD were removed by 50+/-4% and 82+/-2%, respectively. EC is also efficient for decolorization (red-color) and clarification of the PS effluent. Removals of 89+/-4% and 90+/-4% have been measured for total suspended solids and turbidity, respectively. Electrochemical coagulation operated under the optimal conditions involves a total cost of 0.71 USD $ per cubic meter of treated PS effluent. This cost includes energy and electrode consumptions, chemicals, and sludge disposal.     

Experimental design of Fenton and photo-Fenton reactions for the treatment of cellulose bleaching effluents

Multivariate experimental design was applied to the treatment of a cellulose conventional bleaching effluent in order to evaluate the use of the Fenton reagent under solar light irradiation. The effluent was characterised by the general parameters total organic carbon (TOC), chemical oxygen demand and color, and it was analysed for chlorinated low molecular weight compounds using GC–MS. The main parameters that govern the complex reactive system: Fe(II) and H₂O₂ initial concentration, and temperature were simultaneously studied. Factorial experimental design allowed to assign the weight of each variable in the TOC removal after 15 min of reaction. Temperature had an important effect in the organic matter degradation, especially when the ratio of Fenton reagents was not properly chosen. Fenton reagent under solar irradiation proved to be highly effective for these types of wastewaters. A 90% TOC reduction was achieved in only 15 min of treatment. In addition, the GC–MS analysis showed the elimination of the chlorinated organic compounds initially detected in the studied bleaching effluents.     

Role of organic and black carbon in the chemical composition of atmospheric aerosol at European background sites

The mass concentrations of inorganic ions, water-soluble organic carbon, water-insoluble organic carbon and black carbon were determined in atmospheric aerosol collected at three European background sites: (i) the Jungfraujoch, Switzerland (high-alpine, PM_2.5 aerosol); (ii) K-puszta, Hungary (rural, PM_1.0 aerosol); (iii) Mace Head, Ireland (marine, total particulate matter). At the Jungfraujoch and K-puszta the contribution of carbonaceous compounds to the aerosol mass was higher than that of inorganic ions by 33% and 94%, respectively. At these continental sites about 60% of the organic carbon was water soluble, 55–75% of the total carbon proved to be refractory and a considerable portion of the water soluble, refractory organic matter was composed of humic-like substances. At Mace Head the mass concentration of organic matter was found to be about twice than that of nonsea-salt ions, 40% of the organic carbon was water soluble and the amount of highly refractory carbon was low. Humic-like substances were not detected but instead low molecular weight carboxylic acids were responsible for about one-fifth of the water-soluble organic mass. These results imply that the influence of carbonaceous compounds on aerosol properties (e.g. hygroscopic, optical) might be significant.     

Semiconductor-assisted photodegradation of lignin, dye, and kraft effluent by Ag-doped ZnO

This work reports a preliminary study of semiconductor-assisted photochemical degradation of lignin, Remazol Brilliant Blue R and Kraft E1 paper effluent by using ZnO and Ag-doped ZnO photocatalysts. The doped semiconductor was prepared in the reaction media by photoreduction of silver nitrate. With the use of 100 mg of ZnO and 15 mg of Ag-ZnO, almost total decolorization of the dye and lignin samples in reaction times lower than 60 min were observed. Extending the photochemical reaction up to 120 min, the total organic carbon content (TOC) was reduced in 90%. For the paper effluent, a fast decolorization was obtained for relatively short reaction times. However, de TOC reduction was negligible (near of 10%) up to high reaction times (300 min). By using the Ag-ZnO photocatalyst, the toxicity of lignin and Kraft E1 effluent toward E. Coli was completely removed. For the dye, the formation of transient toxic species was observed.     

聚乙烯醇在超临界水氧化中降解

以H2O2为氧化剂用间歇式超临界水氧化装置对聚乙烯醇(PVA)废水进行降解研究。通过正交实验,考察了反应温度、压力、时间及氧化剂过氧倍数对降解效果的影响,并且采用GC/MS对液相降解产物进行表征推测其可能降解途径。结果表明:PVA在SCWO体系中能完全降解,反应温度440℃、压力28 MPa、氧化剂过氧倍数4、反应40 min时,COD去除率为99.03%,出水COD=89.09 mg/L。PVA在SCWO体系中降解为烯烃、烯酮、醇和羧酸类中间产物、最终降解为小分子的饱和直链烷烃类液相产物。     

Evaluation of ion exchange resins for the removal of dissolved organic matter from biologically treated paper mill effluent

In this study, the efficiency of six ion exchange resins to reduce the dissolved organic matter (DOM) from a biologically treated newsprint mill effluent was evaluated and the dominant removal mechanism of residual organics was established using advanced organic characterisations techniques. Among the resins screened, TAN1 possessed favourable Freundlich parameters, high resin capacity and solute affinity, closely followed by Marathon MSA and Marathon WBA. The removal efficiency of colour and lignin residuals was generally good for the anion exchange resins, greater than 50% and 75% respectively. In terms of the DOM fractions removal measured through liquid chromatography–organic carbon and nitrogen detector (LC–OCND), the resins mainly targeted the removal of humic and fulvic acids of molecular weight ranging between 500 and 1000 g mol^?1, the portion expected to contribute the most to the aromaticity of the effluent. For the anion exchange resins, physical adsorption operated along with ion exchange mechanism assisting to remove neutral and transphilic acid fractions of DOM. The column studies confirmed TAN1 being the best of those screened, exhibited the longest mass transfer zone and maximum treatable volume of effluent. The treatable effluent volume with 50% reduction in dissolved organic carbon (DOC) was 4.8 L for TAN1 followed by Marathon MSA – 3.6 L, Marathon 11 – 2.0 L, 21K-XLT – 1.5 L and Marathon WBA – 1.2 L. The cation exchange resin G26 was not effective in DOM removal as the maximum DOC removal obtained was only 27%. The resin capacity could not be completely restored for any of the resins; however, a maximum restoration up to 74% and 93% was achieved for TAN1 and Marathon WBA resins. While this feasibility study indicates the potential option of using ion exchange resins for the reclamation of paper mill effluent, the need for improving the regeneration protocols to restore the resin efficiency is also identified. Similarly, care should be taken while employing LC–OCND for characterising resin-treated effluents, as the resin degradation is expected to contribute some organic carbon moieties misleading the actual performance of resin.     

Advanced oxidation of a pulp mill bleaching wastewater.

The degradation, by several advanced oxidation reactions, of a pulp mill ECF bleaching effluent, was studied. The initial biodegradability of the organic matter present in the effluent, estimated as the BOD5/COD, was low (0.3). When the effluent was submitted to ozonation and to five different advanced oxidation systems (O3/UV, O3/UV/ZnO, O3/UV/TiO2, O2/UV/ZnO, O2/UV/TiO2), the biodegradability increase significantly. After five minutes of reaction, the O3/UV system appears as the most efficient in to transform the organic matter to more biodegradable forms. A similar effect was observed when the effluent was submitted to an activated sludge treatment. The COD, TOC and toxicity reduction correlated well with the biodegradability enhancement after AOPs treatments.     

BAF+常规工艺中砂滤池净水效果研究

以广州某水厂源水为处理对象,研究在曝气生物滤池(BAF)+常规工艺中砂滤池的净水效果。研究表明,砂滤池出水CODMn、NH4+-N的平均值分别为1.19 mg/L和0.08 mg/L;相对于沉淀池出水,砂滤池对上述指标的平均去除率分别为27.41%和63.86%;砂滤池出水NO2--N几乎检测不出。砂滤池对分子量(10 K的溶解性有机物有较好的去除作用;砂滤池中DO下降了1.80 mg/L,分析表明在砂滤池中发生了完全硝化反应。     

Slaughterhouse wastewater treatment in a full-scale system with constructed wetlands.

This work evaluated the performance of a full-scale system with wetlands for slaughterhouse (abattoir) effluent treatment in the State of Hidalgo, México. The treatment system consisted of a primary sedimentation tank, an anaerobic lagoon, and a constructed subsurface-flow wetland, in series. The wetland accounted for almost 30% of the removal of organic matter. In general, the treatment system achieved satisfactory pollutant removals, but the final effluent could not meet the Mexican environmental regulations for fecal coliform counts, five-day biochemical oxygen demand (BOD5), and total suspended solids (TSS). Overall, removal levels were 91%, 89%, and 85% for BOD5, chemical oxygen demand, and TSS, respectively. However, BOD5 in the final effluent (137 mg/L) was higher than the maximum level of 30 mg/L allowed by the regulatory agency. Although organic nitrogen removal levels were approximately 80%, the nitrogen persisted in oxidation state -3 as ammonia-nitrogen, the removal of which was only 9% in the wetland stage. On average, phosphorus removal was null, and, on occasion, the phosphorus concentration in the treated effluent was higher than that of the influent. Coliform reductions in the overall system were high (on the order of 5 logs on average), whereas the coliform removal in the wetland was between 2 to 3.5 logs. The treatment system was also effective at removing pathogens (Vibrio cholerae, Salmonella, and Shigella). Further laboratory tests with the wetland effluent suggest that post treatment in a sand filter stage followed by disinfection with sodium hypochlorite (NaOCl) could help meet the Mexican discharge regulations, particularly the criteria for coliforms and total BOD5.     

Combined treatment of textile effluent using the sequence Phanerochaete chrysosporium-ozone.

Textile effluents cause a high environmental impact when released into the environment without correct treatment. In this work, we have evaluated the capacity of treatment of a textile effluent using a biological and a chemical method using the sequence Phanerochaete chrysosporium-ozone. The fungal treatment was performed by direct incubation of a fungus spore suspension in textile effluent for nine days. Then, the effluent was ozonized at pH 11 and room temperature. Color, total organic carbon, molecular mass distribution and total phenols were determined. In biological experiments, enzymatic activity (lignin peroxidase, manganese peroxidase and laccase) were also monitored. Toxicity tests were carried out with Scenedesmus subspicatus and with Escherichia coli. Good decoloration, total phenols reduction and textile effluent molecular mass reduction were obtained during the process. No significant total organic carbon reduction was observed. The toxicity of the textile effluent was reduced with both test organisms showing no inhibition at the end of the treatment.     

铁盐和铝盐混凝对印染废水生化出水中溶解性有机污染物的去除特性

以三氯化铁和硫酸铝为混凝剂,印染废水二级生化出水为研究对象,并利用XAD-8/XAD-4吸附树脂联用技术将印染废水生化出水中溶解性有机物分为疏水酸、非酸疏水物质、弱疏水物质及亲水物质4类有机物,通过小试实验探讨了2种混凝剂对生化出水中各类溶解性有机物的去除效果及特点。实验结果表明,对于该印染废水的生化出水,溶解性有机物的主要成分是疏水性物质,以DOC表征时占总DOC的75%,其中疏水酸约占41%,疏水性物质也是引起色度的主要物质,所占比例以ADMI7.6表征时为89%,其中以非酸疏水物质的贡献最大,达到52%,并且非酸疏水物质中不饱和双键或芳香环有机物的含量较高。在三氯化铁和硫酸铝各自最佳的混凝条件下,均能够有效去除由疏水性物质（疏水酸和非酸疏水物质）引起的色度,但三氯化铁对弱疏水性物质以及亲水物质的去除率高于硫酸铝,这使得三氯化铁对印染废水生化出水中的溶解性有机物的去除效果优于硫酸铝。并且三氯化铁和硫酸铝混凝工艺均能明显降低生化出水的毒性。     

Treatment of wastewater effluents with Phillipsite-rich tuffs

The presence of abundant zeolites in association with volcanic pumiceous materials in Tererife (Canary Islands) prompted us to study their properties as a water purifying bed for inorganic contaminants, pathogenic bacteria, and soluble organic matter. The experimental model used was a chemical percolation reactor with a constant flux of solution, where the fixation kinetics were studied by comparing the input and the output solutions. The ammonium and phosphate retention values found after 10 days of constant percolation were 70% and 14%, respectively. In addition, a high reduction of soluble organic matter was observed, as well as the total removal of the bacteria species studied. The N-P-K values of the soluble and exchangeable nutrients indicate the potential capacity of the bed as a slow-release fertilizer.     

Improvement of DOC removal by multi-stage AOP-biological treatment

The single and multi-stages advanced oxidation process (AOP)-biological treatments were evaluated to apply for drinking water treatment, especially for the water containing less susceptible dissolved organic carbon (DOC) to ozone, comparing with the ozonation-biological treatment. Minaga reservoir water and the secondary effluent from a Municipal wastewater treatment plant were used as dissolved organic matter (DOM) solutions. DOC removals after 60 min AOP-biological treatment were 62% and 41% in the Minaga reservoir water and the secondary effluent, respectively, whereas those in the ozonation-biological treatment only 40% and 15% of DOC were removed, respectively. The result indicated that the single-stage AOP-biological treatment could improve DOC removal in comparison with the single-stage ozonation-biological treatment. This is because the AOP mineralized both biodegradable dissolved organic carbon (BDOC) produced in the early stage of oxidation and non-biodegradable dissolved organic carbon (NBDOC), whereas only BDOC was mineralized by further ozonation and NBDOC was not oxidized in the ozonation-biological treatment. The multi-stage treatment could not improve DOC removal in comparison with the single-stage treatment in the ozonation-biological treatment for the secondary effluent containing less susceptible DOC to ozone. However, the multi-stage AOP-biological treatment significantly reduced DOC and achieved 71% of DOC removal by 4 times repetition of 15 min oxidation, whereas DOC removal was 41% in the single-stage AOP-biological treatment for the same oxidation time. The improvement of DOC removal by the multi-stage AOP-biological treatment was due to BDOC removal as a radical scavenger by subsequent biological treatment in the early stage of oxidation and direct mineralization in the latter stage of oxidation.     

Removal of organic compounds during treating printing and dyeing wastewater of different process units

Wastewater in Shaoxing wastewater treatment plant (SWWTP) is composed of more than 90% dyeing and printing wastewater with high pH and sulfate. Through a combination process of anaerobic acidogenic [hydraulic retention time (HRT) of 15h], aerobic (HRT of 20h) and flocculation-precipitation, the total COD removal efficiency was up to 91%. But COD removal efficiency in anaerobic acidogenic unit was only 4%. As a comparison, the COD removal efficiency was up to 35% in the pilot-scale upflow anaerobic sludge bed (UASB) reactor (HRT of 15h). GC-MS analysis showed that the response abundance of these wastewater samples decreased with their removal of COD. A main component of the raw influent was long-chain n-alkanes. The final effluent of SWWTP had only four types of alkanes. After anaerobic unit at SWWTP, the mass percentage of total alkanes to total organic compounds was slightly decreased while its categories increased. But in the UASB, alkanes categories could be removed by 75%. Caffeine as a chemical marker could be detected only in the effluent of the aerobic process. Quantitative analysis was given. These results demonstrated that GC-MS analysis could provide an insight to the measurement of organic compounds removal.     

Biological solids reduction using the Cannibal process.

A laboratory study of the Cannibal process was undertaken to determine if the Cannibal system would generate less sludge compared with a conventional activated sludge system. Side-by-side sequencing batch reactors were operated--one using the Cannibal configuration and the other as conventional activated sludge. It was found that the Cannibal process generated 60% less solids than the conventional activated sludge system, without any negative effect on the effluent quality or the settling characteristics of the activated sludge. The oxygen uptake rate for the centrate from the Cannibal bioreactor showed that readily biodegradable organic matter was released from the recycled biomass in the Cannibal bioreactor. It is proposed that the mechanism for reduced solids from the Cannibal system is that, in the Cannibal bioreactor, iron is reduced, releasing iron-bound organic material into solution. When the Cannibal biomass is recirculated back to the aeration basin, the released organic material is rapidly degraded.     

Uptake of selected PAHs from contaminated soils by rice seedlings (Oryza sativa) and influence of rhizosphere on PAH distribution

The uptake of selected polycyclic aromatic hydrocarbons (PAHs) by rice (Oryza sativa) seedlings from spiked aged soils was investigated. When applied to soils aged for 4 months, naphthalene, phenanthrene, and pyrene exhibited volatilization loss of 98, 95, and 30%, respectively, with the remaining fraction being fixed by soil organic matter and/or degraded by soil microbes. In general, concentrations of the three PAHs in rice roots were greater than those in the shoots. The concentrations of root associated PHN and PYR increased proportionally with both soil solution and rhizosphere concentrations. PAH concentrations in shoots were largely independent of those in soil solution, rice roots, or rhizosphere soil. The relative contributions of plant uptake and plant-promoted rhizosphere microbial biodegradation to the total mass balance were 0.24 and 14%, respectively, based on PYR concentrations in rhizosphere and non-rhizosphere soils, the biomass of rice roots, and the dry soil weight.