RESUMEN
This study aims to investigate the influence of the coexistence of halogen ions (bromide/iodide) and biological source matters on the speciation and yield of trihalomethanes (THMs), haloacetic acids (HAAs), and N-nitrosodimethylamine (NDMA) during the ozonation and subsequent chlorination of water. The results show that the concentrations of brominated THMs and iodinated THMs increased with increasing bromide and iodide concentration. These results may be attributed to the higher reactivity of hypobromous acid and hypoiodous acid generated from the ozonation and subsequent chlorination in the presence of bromide or iodide ions. The presence of bromide increased the species of brominated HAAs. There was a shift from chlorinated HAAs to brominated HAAs after increasing the concentration of bromide. The effect of iodide on HAA formation was more complex than bromide. For most samples, the concentration of total HAAs (T-HAAs) increased to the maximum and then decreased with increasing iodide concentration. The components of the organic precursors also significantly influenced the formation of brominated and iodinated disinfection by-products (Br-DBPs and I-DBPs). Humic acids produced more CHBr3 (596.60 µg/L) than other organic materials. Microcystis aeruginosa cells produced the most tribromoacetic acid (TBAA, 84.16 µg/L). Furthermore, the yield of NDMA decreased with increasing bromide concentration, indicating that the formation of NDMA was inhibited by the high concentration of bromide.
Asunto(s)
Acetatos/química , Bromuros/química , Cloro/química , Dimetilnitrosamina/química , Yoduros/química , Oxidantes/química , Ozono/química , Trihalometanos/química , Biopolímeros , ADN , Desinfección/métodos , Aceites de Pescado , Halogenación , Sustancias Húmicas , Microcystis , Albúmina Sérica Bovina , Almidón , Purificación del Agua/métodosRESUMEN
Water sources are micro-polluted by the increasing range of anthropogenic activities around them. Disinfection byproduct (DBP) precursors in water have gradually expanded from humic acid (HA) and fulvic acid to other important sources of potential organic matter. This study aimed to provide further insights into the effects of microbially derived organic matter as precursors on iodinated trihalomethane (I-THM) speciation and formation during the biological treatment of micro-polluted source water. The occurrence of I-THMs in drinking water treated by biological processes was investigated. The results showed for the first time that CHCl2I and CHBrClI are emerging DBPs in China. Biological pre-treatment and biological activated carbon can increase levels of microbes, which could serve as DBP precursors. Chlorination experiments with bovine serum albumin (BSA), starch, HA, deoxyribonucleic acid (DNA), and fish oil, confirmed the close correlation between the I-THM species identified during the treatment processes and those predicted from the model compounds. The effects of iodide and bromide on the I-THM speciation and formation were related to the biochemical composition of microbially derived organic precursors. Lipids produced up to 16.98µgL(-1) of CHCl2I at an initial iodide concentration of 2mgL(-1). HA and starch produced less CHCl2I at 3.88 and 3.54µgL(-1), respectively, followed by BSA (1.50µgL(-1)) and DNA (1.35µgL(-1)). Only fish oil produced I-THMs when iodide and bromide were both present in solution; the four other model compounds formed brominated species.
Asunto(s)
Bacterias/metabolismo , Halogenación , Trihalometanos/química , Microbiología del Agua , Animales , Bromuros/química , Desinfectantes/química , Agua Potable/química , Agua Potable/microbiología , Yoduros/química , Trihalometanos/análisisRESUMEN
This study describes the change of organic degradation capability and soluble microbial products (SMP) generated in activated sludge under continuous exposure to Zn (II) in a sequencing batch reactor (SBR). In 338 days of operation, the added Zn (II) concentrations were gradually increased from 50 to 100, 200, 400 to 600 and 800 mg/L. Results showed that after adaptation, the activated sludge could endure 400mg/L Zn (II) without showing evident reduction in organic degradation ability (92±1% of chemical oxygen demand (COD) removal in stable state). However, when 600 and 800 mg/L Zn (II) were applied, the effluent water quality significantly deteriorated. Meanwhile, under increasing Zn (II) concentrations, the SMP content in the activated sludge, together with its main biochemical constituents, first increased slightly below 400mg/L of Zn (II), then rose sharply under 600 and 800 mg/L Zn (II). Furthermore, a close correlation was found between SMP content and effluent soluble COD in both the Experimental Reactor and Control Reactor. In addition, the Zn (II) concentrations in the effluent and SMP extraction liquid were further analyzed and discussed to reveal the role that SMP constituents played in defense and resistance to the toxicity of Zn (II).
Asunto(s)
Reactores Biológicos/microbiología , Aguas del Alcantarillado/microbiología , Contaminantes Químicos del Agua/toxicidad , Zinc/toxicidad , Análisis de la Demanda Biológica de Oxígeno , ADN/análisis , Sustancias Húmicas , Polisacáridos/análisis , Proteínas/análisis , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/metabolismo , Zinc/análisisRESUMEN
The effect of different concentrations of nickel ions (Ni(2+), 0, 10, 40 and 80 mg/L) on the anaerobic methane production of water hyacinth were investigated. Under these four concentrations, the methane production in 40 d was 2,275, 2,703, 3,210 and 2,481 mL, respectively. This situation illustrated that the Ni(2+) promoted the growth of hydrogen-producing acetic acid bacteria and methanogenic bacteria, even at high concentrations (i.e. 40-80 mg/L). The highest methane production per unit weight water hyacinth reached 206 mL/gTS with 40 mg/L Ni(2+). Meanwhile, the modified Gompertz and Logistic equations were applied to describe the effect on anaerobic culture of Ni(2+). According to these models, the values of methane production potential (mL) for four concentrations were in the following order: 40 mg/L (3,123.42 ± 60.08) > 10 mg/L (2,541.16 ± 46.94) > 80 mg/L (2,432.36 ± 40.18) > 0 mg/L (2,238.10 ± 31.90). According to the analysis of the digestate, the residual concentration of Ni(2+) was approximately 1.05-4.9 mg/L, which was relatively low compared with the Ni(2+) concentrations in the raw feedstock. The results would provide academic guidance and technical support for treatment of water hyacinth with an accumulation of heavy metals.
Asunto(s)
Eichhornia/efectos de los fármacos , Eichhornia/metabolismo , Gases/metabolismo , Metano/metabolismo , Níquel/toxicidad , Contaminantes Químicos del Agua/toxicidad , Anaerobiosis , Biocombustibles , Relación Dosis-Respuesta a Droga , Fermentación , Metano/química , Modelos Biológicos , Níquel/administración & dosificación , Factores de Tiempo , Contaminantes Químicos del Agua/administración & dosificaciónRESUMEN
INTRODUCTION: Effluent organic matter from biological wastewater treatment plants is composed of degradation products and soluble microbial products (SMP). Protein, polysaccharide, humic acid, and DNA were major biomolecules of SMP. Little is known about the effects of SMP as microbially derived precursors on disinfection byproduct formation and speciation in biologically treated wastewater. In addition, there has never been any attempt to directly chlorinate the major biomolecules of SMP. MATERIALS AND METHODS: In this study, model compounds (bovine serum albumin, starch, DNA, and humic acid) and SMP collected from a sequencing batch reactor (SBR) were chlorinated to verify the trihalomethane and haloacetic acid species that were produced from them. RESULTS AND DISCUSSION: The results showed that chloroform, dichlorobromomethane, dichloroacetic acid, and trichloroacetic acid were generated from the chlorination of SMP in the SBR, and there was a close relationship between the species predicted from the model chemical compounds and those obtained from the SMP.
Asunto(s)
Acetatos/química , Trihalometanos/química , Microbiología del Agua , Contaminantes del Agua/análisis , Purificación del Agua/métodos , Reactores Biológicos , Cloro/química , Desinfección , Contaminantes del Agua/químicaRESUMEN
Static experiments were performed to investigate the adsorption characteristics of ammonium by suspended mineral matters (SPM). Three kinds of suspended mineral matters including montmorillonite, kaolin and the particles separated from the sediments of the Taihu Lake were used as the sorbent. The experiments show that the equation could be gotten within 30 min, and that the ammonium adsorption on mineral particles conformed to Herry isotherm. The parting coefficient of the adsorption about ammonium could reach 548.30, 287.36, 191.27 L/kg in experimental condition that there were 1 000 mg/L mineral particles and 1.0 mg/L ammonium in water with pH 7.00. Some effectors such as temperature, pH and salinity of the water on the adsorption about ammonium were observed. The results show that the quantity of adsorbed ammonium slightly decrease with the increasing of temperature and salinity, and greatly do with increasing of pH. The quantity decrease rapidly also with the increasing of the content of mineral particles below 1 000 mg/L.
Asunto(s)
Bentonita/química , Eutrofización , Nitrógeno/química , Compuestos de Amonio Cuaternario/química , Purificación del Agua/métodos , Adsorción , Caolín/químicaRESUMEN
A novel adsorbent made by cellulose acetate was developed. Preparation method, structure, and adsorbing characterization of the adsorbent were discussed. SEM results showed that the surface of round adsorbent was stable membrane of cellulose acetate, free from obvious cracks, holes, or other defects; while the cross section of the adsorbent was meshy and a lot of cavities were found. The adsorption results of 4 organochlorinated pesticides, such as Dieldrin, Aldrin, Endrin and Heptachlor, show that the adsorbent has higher efficient for organic pollutants, the adsorption rate is about 85% after 12 h. The adsorption rate is faster with the higher lgKow, and the removal efficiency of Heptachlor and Aldrin is up to 99% after 0.5h. The adsorbent can be used to remove persistent organic pollutants effectively.