Enhancement of Dissolved Organic Matter Bioavailability by Sunlight and Its Role in the Carbon Cycle of Lakes Superior and Michigan

The degree to which sunlight and microbes interact in the cycling of dissolved organic matter (DOM) of natural waters is unclear. During 1999 and 2000, the effects of sunlight on the lability of DOM in two of the Laurentian Great Lakes were examined. Bacteria-free (< 0.2 μm) water samples collected in Lake Superior and Lake Michigan were exposed to ambient sunlight for several days and subsequently inoculated (1:10) with < 1.0 μm lake water containing natural bacteria and assayed for bacterial growth rates (³H-leucine incorporation into protein) in the dark. Exposure of water collected from offshore surface layers to sunlight caused a net reduction of DOM bioavailability (bacterial growth ∼20 to 30% of dark control), whereas both exposure of deep water and river water to sunlight resulted in a net enhancement of DOM bioavailability (bacterial growth ∼150 to 260% of dark control). Irradiated water from nearshore exhibited an intermediate response in terms of changes in DOM bioavailability (bacterial growth ∼75 to 115% of dark control). Despite the reduction of DOM bioavailability in surface waters by sunlight exposure in the short-term (relative to dark control), subsequent incubation of these waters in the dark increased bacterial production rates relative to in situ rates, suggesting that the net effect of exposure to sunlight, even in surface waters, was to increase DOM bioavailability. Rapid and sustained photochemical alterations of DOM bioavailability occurring in the euphotic zone of natural waters should accelerate the turnover of surface water, older deep water, and refractory terrigenous carbon.     

管网水细菌再生长限制因子的特性与比较

管网水细菌再生长的研究是近年来水处理领域的研究热点。分析了管网中细菌再生长机制及其影响因素,系统论述和比较了可同化有机碳(AOC)、磷与细菌再生长间的关系,简述了细菌再生长潜力(BRP)测定方法与特性,并就管网水细菌再生长的评价和制水工艺优化提出了建议。     

On-site greywater treatment and reuse in multi-storey buildings.

The paper presents a study of a pilot plant treating light greywater for seven flats. The pilot plant combines biological treatment (RBC) with physicochemical treatment (sand filtration and disinfection). The pilot plant produced effluent of excellent quality, meeting the urban reuse quality regulations, and was very efficient in TSS turbidity and BOD removal: 82%, 98% and 96%, respectively. COD removal was somewhat lower (70-75%) indicating that the greywater may contain slowly-biodegradable organics. The RBC (attached growth biological system) was able to retain most of the solids as a result of bioflocculation; further it was proven to have very stable and reliable performance. Faecal coliforms and heterotrophic reductions were very high (100% and 99.99%, respectively) producing effluent that also met drinking water standards. The combination of low organic matter, nutrients and microbial indicators reduces the regrowth and fouling potentials in the reuse system, thus ensuring safe reuse of the treated greywater for toilet flushing.     

Dissolved Organic Matter in the Great Lakes: Role and Nature of Allochthonous Material

Dissolved organic matter (DOM) quality and the modifying influence of light on DOM bioavailability were investigated along a natural gradient of allochthonous influence in the lower Great Lakes. Using parallel factor analysis (PARAFAC), three DOM fluorophores were identified. One fluorophore, previously identified as peak C, was of allochthonous (component 1) origin and two previously uncharacterized fluorophores were identified as autochthonous (components 2 and 3). Component 1 was photoreactive and the dominant form in creek water samples while components 2 and 3 were dominant in Hamilton Harbour and lake water samples. Components 2 and 3 showed limited photoreactivity. Exposure to full spectrum irradiance decreased the average molecular weight of DOM (i.e., increased the absorbance ratio (a254:a365)) for all water samples. DOM bioavailability was lowest in creek and highest in lake water samples and was inversely related to DOM average molecular weight. Photomodification of DOM resulted in higher bacterial activity although these differences were not significantly different. This suggests that light plays a significant role in the cycling of terrestrially-derived DOM and to a certain extent autochthonous DOM, potentially increasing metabolism of both terrestrially and microbially derived DOM in the Great Lakes aquatic ecosystems.     

Evaluating the potential of biofilm control in water supply systems by removal of phosphorus from drinking water.

Effect of microbially available phosphorus (MAP) on biofilm development in drinking water systems was investigated at the pilot-scale experiments over 3 years. Completely mixed biofilm reactors Propella (water detention time 24 h, flow rate 0.25 m s(-1), PVC pipe coupons) were used as water distribution network models. Four experimental runs were carried out with water containing different levels of phosphorus which was limiting nutrient for bacterial growth. Positive correlation between MAP in the inlet water and heterotrophic plate count (correlation coefficient 0.95) in biofilm, as well as for the total bacteria number (correlation coefficient 0.71), was observed. However, our experiments showed that removal of phosphorus down to very low levels (below detection limits of chemical method and MAP < 1 microg L(-1) was not an efficient strategy to eliminate bacterial regrowth and biofilm formation (< 51,00,000 cells/cm2) in drinking water supply systems.     

饮用水生物稳定性控制指标探讨

结合给水管网中饮用水微生物再生长现象,分析了AOC作为反映饮用水生物稳定性的替代参数所存在的问题。根据饮用水处理系统中微生物营养的种类及特点,以及磷在微生物生长和代谢过程中的关键作用,提出同时检测和控制磷含量来保证饮用水生物稳定性的观点,并对磷和AOC共同作为饮用水生物稳定性控制指标的可行性进行了探讨。     

溶解性有机质对低影响开发设施运行影响的研究进展

低影响开发(LID)设施在治理城市内涝和径流污染中发挥重要作用，在我国海绵城市建设中应用广泛。溶解性有机质(DOM)是一类具有较强的吸附、络合作用的溶解态物质，其质量占比高达径流污染物的50%以上。为阐明DOM对LID设施运行的影响，结合国内外研究现状及进展，综述DOM自身性质及其对LID设施中重金属(HMs)、持久性有机物(POPs)的归趋以及对微生物环境的影响，指出DOM会通过吸附、络合与HMs、POPs作用，造成LID设施填料吸附位点饱和、填料堵塞、微生物相对丰度(RAs)改变等。本研究旨在为LID设施设计和运行优化提供参考。     

Membrane fouling and selectivity mechanisms in effluent ultrafiltration coupled with flocculation.

Membrane filtration is adequate for producing disinfected clear water suitable for various kinds of applications. However, fouling of membranes is the main limitation. The scope of the present study is to examine the effect of iron coagulation of primary wastewater effluent on membrane filtration, in parallel to fouling characterization of the iron itself. The fouling of ultrafiltration membranes by colloidal iron hydroxide-oxide has been studied by measuring the pore streaming potential of PES UF membrane. pH 5.5 (charge neutralization zone) provided better removal and lower fouling intensity than pH 7.8 (sweep coagulation zone), but the internal clogging at acidic pH was higher. Fouling of the membrane as measured by flux reduction was usually accompanied by a positive change in zeta potential and iso-electric point (IEP) of the membrane. An initially large change in zeta potential (without charge reversal) was seen even after relatively small amounts of iron solution were filtered through the membrane. A control experiment showed this is not due to iron adsorption equilibrium, but should probably be attributed to fouling. Change in zeta potential, can be used as an indicator for commencement of fouling even for small flux reductions. UF membrane critical flux after iron filtration can be evaluated more accurately by zeta potential than pressure drop or change in iron concentration.     

组合工艺控制有机物及消毒副产物前体物的特性研究

通过XAD-8树脂将水中有机物分成疏水性、亲水性两部分,对传统常规处理工艺(混凝气浮、过滤)和深度处理工艺(臭氧氧化、生物活性炭)出水的DOC,UV254THMFP,HAAFP指标以及疏水、亲水有机物去除率进行了检测分析。结果表明,生物活性炭(BAC)单元工艺能同时去除疏水性和亲水性两种有机物,且两者去除率均为最高。其次去除效果较好的是传统的常规工艺。臭氧工艺具有将天然的疏水性有机物氧化成可生化降解的亲水性小分子有机物的特点,在预臭氧+常规以及O3-BAC组合工艺中,起到了强化去除有机物和消毒副产物前体物的效果。     

Concentration of nutrients from urine and reject water from anaerobically digested sludge.

Experiments with concentration of nutrients from source separated urine and reject water from digestion of sludge in sewage treatment plants (STP) have been performed in laboratory and pilot scale. The methods tested were membrane filtration with reverse osmosis (RO), evaporation, and precipitation of phosphorus and distillation of ammonia. In membrane filtration, pre-filtration with particle separation at 5-10 microm was enough to avoid clogging of the membranes. Separation of phosphorus (P), potassium (K) and sulphur (S) was almost 100%, while separation of nitrogen (N) was dependent on pH. The capacity of flux increased with temperature and pressure. In evaporation, all P, K and S were still in the concentrate, while pH had to be decreased to 4.5 to avoid significant loss of N. In precipitation and distillation, about 90% of P could be recovered from urine as magnesium ammonium phosphate (MAP) just by adding MgO. For the reject water pH was first increased by aeration to remove CO2. Ammonium can be distilled from the water phase after precipitation of MAP, without further increase of pH. At least 80-90% of N can be distilled in 5-10% of the total volume. The article also discusses the quality of different products, cost of separation, and energy and chemical demand.     

Effect of bacterial growth stage on resistance to chlorine disinfection

The mechanisms and factors that affect microbial resistance to chlorine disinfection have not been fully elucidated. In this study, we investigated the impact of the cell growth stage on chlorine disinfection efficiency. Specifically, we evaluated the impact of the growth stage on chlorination resistance by comparing the inactivation efficiencies of two indicator bacterial strains (Escherichia coli K12 and Escherichia coli O157:H7) obtained from various growth phases, using Chick-Watson kinetic parameters. For both E. coli strains (K12 and O157:H7), the inactivation rate constants are the lowest at stationary phase (0.19 and 0.32) compared to those at initial lag (0.54 and 0.76) and exponential growth phase (0.63 and 0.69), respectively. These results suggested that the abundance of resistant subpopulations increases at stressed stationary conditions and E. coli cells obtained from the stationary growth phase exhibited more resistance and lower inactivation efficiency compared to those from the lag and exponential phases. This implies that microbes in wastewater treatment process with varying solids retention times (SRTs, which indicate growth rates) may show different extents of chlorine resistance. Comparison of the coefficient of dilution (n) values in both E. coli strains for the various growth phases suggest that cells seem to be more sensitive to disinfectant concentration at the stationary-lag phase than that at the exponential stage. Comparing the two E. coli strains, higher inactivation rates were observed for the pathogenic O157:H7 than for K12 at different stages of growth. The strain-to-strain variability in survivability to chlorine exposure has to be considered when selecting indicator microorganisms for water quality monitoring.     

The effect of detachment on biofilm structure and activity: the oscillating pattern of biofilm accumulation.

In our previous papers we have demonstrated that biofilm structure never reaches a steady state in biofilm reactors; in this paper we link this fact to biofilm detachment and to the oscillating pattern of biofilm accumulation. In one respect reactors supporting suspended microbial growth and reactors supporting attached microbial growth (biofilms) are similar: in both the biomass accumulates in the reactor and is disposed of with the effluent. However, while in reactors with suspended microbial growth biomass accumulation and disposal occur simultaneously, in biofilm reactors these two processes are separated in time. Biomass accumulation in biofilm reactors shows a distinct pattern composed of three phases: (1) growth, (2) detachment, (3) regrowth. Despite this distinct pattern of biofilm accumulation observed at the microscale, biofilm reactors do reach a steady state of substrate removal.     

The development of geotextiles incorporating slow-release phosphate beads for the maintenance of oil degrading bacteria in permeable pavements.

The development of a self-fertilising geotextile mat designed to provide a sustained slow-release of required inorganic nutrients for the growth of oil degrading microorganisms in porous pavement systems (PPS) is reported. The system comprises a geotextile spun from polymer fibres containing spherical phosphated polymer beads that release phosphate upon contact with water at a desirable level for microbial growth. Initial results using model PPS have shown that the self-fertilising geotextile system works extremely effectively as increased microbial activity has been observed throughout the experiment, illustrating that the oil-degrading bacteria can effectively utilise this polymer composite as a suitable nutrient source.     

黄河下游某市给水管网水质生物稳定性分析

考察了黄河下游某市给水管网水质的生物稳定性。结果表明:2011年2～7月,生物可同化有机碳AOC在8.7～328.7μg/L,81.3%的检测数据AOC<100μg/L,其值随季节变化、水温升高而升高。AOC P17在AOC组成中占优势,季节变化特征较AOC NOX明显。以引黄水库作为水源、处理工艺不同的两水厂给水管网可生物降解溶解性有机碳BDOC存在差异。黄河下游城市给水管网水质生物稳定性总体水平较好,管网不同取样点细菌再生长限制性因子有差异,AOC、磷及其他无机营养元素均有可能成为限制性因子。     

Characterization of microparticles in raw, treated, and distributed waters by means of elemental and particle size analyses.

The elemental composition and particle size distribution of suspended particles in raw water, treated water, and distributed water were determined to understand the behavior of particles during the water treatment-distribution process. The weight of suspended particles collected on a 0.6-microm filter was 1.1 times (raw water), 1.4 times (treated water), and 1.5 times (distributed water) that collected on a 2.7-microm filter, suggesting that smaller particles may remain after conventional water treatment. Organic suspended particles were removed less efficiently than inorganic suspended particles. After sand filtration, the Al content in the fixed suspended solids (FSS) markedly increased, indicating that either a small percentage of aluminium floc passed through during sand filtration or dissolved aluminum precipitated after sand filtration. The Mn and Fe concentrations increased after chlorination. The percentages of carbon and nitrogen in the volatile suspended solids (VSS) were roughly the same in the raw, treated, and distributed waters. The carbon/nitrogen/phosphate/VSS ratios indicated that the VSS of the suspended particles consisted of organic matter originating from microorganisms. The major constituents of the FSS in the treated and distributed waters were compounds of Fe, Al, Ca, Mg, and Mn, but these compounds accounted for only 16% or less of the FSS in raw water, indicating the existence of Si compounds. In distribution pipes, the total suspended solids concentration, especially the FSS concentration, was higher than that of water just after treatment. The Fe concentration in distributed water increased, probably due to oxidation and rusting of iron pipes.     

Evaluation of the purification capacity of nine portable, small-scale water purification devices.

A test was performed to evaluate the microbial and chemical purification capacity of nine portable, small-scale water purification filter devices with production capacity less than 100 L/h. The devices were tested for simultaneous removal capacity of bacteria (cultured Escherichia coli, Clostridium perfringens, Klebsiella pneumoniae and Enterobacter cloacae), enteric protozoans (formalin-stored Cryptosporidium parvum oocysts), viral markers (F-RNA bacteriophages) and microcystins produced by toxic cyanobacterial cultures. In general, the devices tested were able to remove bacterial contaminants by 3.6-6.9 log10 units from raw water. Those devices based only on filtration through pores 0.2-0.4 microm or larger failed in viral and chemical purification. Only one device, based on reverse osmosis, was capable of removing F-RNA phages at concentrations under the detection limit and microcystins by 2.5 log10. The present study emphasised the need for evaluation tests of water purification devices from the public safety and HACCP (Hazard Analysis and Critical Control Point) points of view. Simultaneous testing for various pathogenic/indicator microbes and microcystins was shown to be a useful and practical way to obtain essential data on actual purification capacity of commercial small-scale drinking-water filters.     

Evaluation of a MF membrane system composed of pre coagulation-sedimentation and chlorination for water reuse.

In this research, we investigated the variation of transmembrane pressure and permeate water quality in pre-coagulation and sedimentation with iron based coagulant, and chlorination of feed water for PVDF (Polyvinylidene fluoride) based MF membrane filtration. NaCIO was fed to the membrane module at a dosage of 0.5 mg/L and maintained during filtration. To observe the effect of raw water, three types of raw and processed waters, including river surface water, coagulated water and coagulated-settled water, were employed. In the case of river surface water, the transmembrane pressure increased abruptly in 500 hours operation. On the contrary, no significant increase in transmembrane pressure was observed for coagulated water and coagulated-settled water for 1200 hours operation. The turbidity of permeate was lower than the detection limit for all applied waters. The removal efficiency for humic substances in coagulated water and coagulated-settled water was approximately ten times higher than that in surface river water. And, the removal efficiency for TOC and DOC was approximately two times higher than that in surface river water. From the results of the operation, it can be observed that it is possible to maintain stable operation at 0.9 m(3)/m(2)-day filtration flux through a combination of pre-coagulation and pre-chlorination. However, the water quality of permeate was the best when the pre-coagulation-sedimentation process was combined with pre-chlorination. With respect to fouling reduction and operation efficiency increase in membrane filtration, the pre-coagulation/sedimentation process is a promising alternative.     

Fluorescence analysis of dissolved organic matter in natural,waste and polluted waters—a review

Dissolved organic matter (DOM) in aquatic systems originates from a range of sources. Some is allochthonous, transported from the surrounding landscape to the water body, and is derived from and influenced by the geology, land use and hydrology of its origin. Some is created in situ through microbial activity, which may provide an independent source of organic matter, or a recycling mechanism for that which has been transported into the water body. The relative contribution of each source depends upon the location and environmental conditions within and without the water body. Human activity is also a source of DOM, much of which is believed to be labile, which can enter the aquatic system through direct point discharges, diffuse leaching and aerial dispersal. Fluorescence spectroscopy can provide an excellent tool to source DOM fractions, and to monitor and understand DOM transformations in aquatic systems, as much DOM has an intrinsic fluorescence. In particular, recent advances in optical technology, enabling rapid investigation of shorter wavelengths, have enabled more detailed characterization of organic material and its reactions in water. In this article, we review the use of fluorescence spectroscopic techniques to measure the intrinsic fluorescence of organic matter and the application of fluorescent DOM analysis in marine waters, freshwaters and wastewaters. Copyright © 2007 John Wiley & Sons, Ltd.     

Variations in microbial community during nitrogen removal by in situ oxygen-enhanced indigenous nitrogen-removal bacteria

In this study, the enclosure system exhibited perfect nitrogen removal performance with in situ oxygen-enhanced indigenous aerobic denitrifying bacteria in an enclosure experiment. We explored changes in the microbial community during the nitrogen removal process using the MiSeq high-throughput sequencing technology. The results revealed a total of 7974 and 33653 operational taxonomic units (OTUs) for water and sediment systems, respectively, with 97% similarity. The OTUs were found to be affiliated with eight main phyla (Proteobacteria, Actinobacteria, Cyanobacteria, Bacteroidetes, Planctomycetes, Chloroflexi, Firmicutes, and Actinobacteria). The diversity of the enhanced system was found to be higher than that of the control system. Principal component analysis (PCA) revealed that significant spatial and temporal differences were exhibited in the microbial community during nitrogen removal in the enclosure experiment. Redundancy analysis (RDA) indicated that physical parameters (temperature, dissolved oxygen, and pH), nitrogen (total nitrogen and nitrate), functional genes (nirK and nirS), and dissolved organic carbon (DOC) were the most important factors affecting bacterial community function and composition. Lastly, the results suggested that the variation in the microbial community could be analyzed through the MiSeq high-throughput sequencing technology, which may provide technical support for future field tests.     

Ultrafiltration for environmental safety in shellfish production:A case of bloom emergence

The process of ultrafiltration(UF) of natural seawater often encounters the problems of variation in water quality and coastal blooms. To validate the feasibility of UF in shellfish farms, this study compared the hydraulic performance and pollutant removal efficiency of the UF process with those of the commonly used treatments that combine several filtration steps with ultraviolet(UV) disinfection. The comparison was conducted in the cases of natural seawater and a coastal bloom. Given that the UF process encountered the specific type of pollution, this study evaluated the filtration performance of the UF process and the retention of total suspended solids(TSS), bacteria, phytoplankton, and zooplankton. A real coastal bloom was considered in the case study of an experimental shellfish hatchery/nursery in France. The results show that both treatments were able to eliminate approximately 50% of TSS. However, in contrast with UV treatment combined with filtration, the UF process retained total amounts of phytoplankton, zooplankton, and bacteria in the bloom. Although the hydraulic performance of the UF process was impacted by the coastal bloom, the fouling was eliminated through chemical cleaning conducted at a frequency less than once per 12 h.Despite the severe pollution, this study confirmed the pollution resistance and treatment performance of the UF process, indicating that UF has the potential to enhance the biosecurity level.