Removal of NOM in the different stages of the water treatment process

Natural organic matter (NOM) is abundant in natural waters in Finland and in many ways affects the unit operations in water purification. In this study, the organic matter content in water in different stages of a full-scale treatment process over 1 year was measured. The full-scale treatment sequence, studied at the Rusko water treatment plant in Tampere, Finland, consisted of coagulation, flocculation, clarification by sedimentation or flotation, activated carbon (AC) filtration, and disinfection. High-performance size exclusion chromatography (HPSEC) was used for separation to determine changes in the humic substances content during the purification process. In addition, total organic carbon (TOC), KMnO4-number, and UV-absorbance at wavelength 254 nm (UV254) were measured. High molecular weight (HMW) matter was clearly easier to remove in coagulation and clarification than low molecular weight (LMW) matter. Furthermore, depending on the regeneration of the activated carbon filters, activated carbon filtration was effective to a degree but did not remove most of the lowest molecular weight compounds. Significant correlation was established among HPSEC, KMnO4, UV254 absorbance, and TOC. HPSEC proved to be a fast and relatively easy method to estimate NOM content in water and, in fact, gave more information than traditional methods on the type of NOM in a water sample. It also helped the process performance follow-up.     

Removal of hydrocarbons from Nile water

The need to remove hydrocarbons from water supply sources raises questions on the efficiency of the present water treatment processes in removing hydrocarbons. Therefore, the effectiveness of physicochemical processes involving chlorination, chemical coagulation and sand filtration were investigated. The effect of variable filtration media was also examined. In addition, the use of an activated carbon column was considered, and the effect of different retention times was evaluated. Results of this study showed that chemical coagulation using alum and Nalco removed only 32% of the total hydrocarbons and 80% of turbidity. Use of sand and a mixture of anthracite and sand filters showed additional removal of hydrocarbons and turbidity during the continuous filtration process. Increasing the anthracite depth relative to the total effective filtration depth increases the efficiency of the filter. Adsorption on granular activated carbon was shown to be an effective means for the removal of hydrocarbons. Results obtained indicated that the carbon adsorption capacity increases linearly as the retention time increases.     

Removal of trace organic contaminants from domestic wastewater: A meta-analysis comparison of sewage treatment technologies

Trace organic contaminants (TrOCs), such as endocrine disrupting compounds (EDCs) and pharmaceuticals and personal care products (PPCPs), represent global threats to aquatic animals and ecosystems. A major source of TrOCs in the aquatic environment is via the discharge of treated sewage, so there is an urgent need to evaluate the comparative efficiencies of the most widely used sewage treatment technologies as regards elimination of these compounds from wastewater. To address this need, 976 published articles were compiled focusing on estimates of removal (%) for 20 common environmental TrOCs, from five major sewage treatment technologies: conventional activated sludge (CAS), oxidation ditch (OD), membrane bioreactor (MBR), ponds and constructed wetlands (PCW), and trickling biological filters (TBF). A quantitative meta-analysis was performed to compare standardized relative removal efficiencies (SREs) of the compounds amongst these technologies, and where possible potential sources of heterogeneity were considered (e.g., flow rates and chemical sorption potential). The results indicate that the most widely used CAS treatment and the less common TBF provide comparatively poor overall removal of common organic micropollutants. Membrane bioreactors appear to be capable of achieving the greatest overall removal efficiencies, but the sustainability and economic viability of this option has been questioned. Treatment with OD systems may be more economical while still achieving comparatively high removal efficiencies, and the analysis revealed OD to be the best option for targeting highly potent estrogenic EDCs. This study offers a unique global assessment of TrOC removal via leading sewage treatment technologies, and is an important step in the identification of effective options for treating municipal sewage.     

Removal of copper from water using limestone filtration technique. Determination of mechanism of removal

This paper discusses heavy metal removal from wastewater by batch study and filtration technique through low-cost coarse media. Batch study has indicated that more than 90% copper (Cu) with concentration up to 50 mg/l could be removed from the solution with limestone quantity above 20 ml (equivalent to 56 g), which indicates the importance of limestone media in the removal process. This indicates that the removal of Cu is influenced by the media and not solely by the pH. Batch experiments using limestone and activated carbon indicate that both limestone and activated carbon had similar metal-removal efficiency (about 95%). Results of the laboratory-scale filtration technique using limestone particles indicated that above 90% removal of Cu was achieved at retention time of 2.31 h, surface-loading rate of 4.07 m3/m2 per day and Cu loading of 0.02 kg/m3 per day. Analyses of the limestone media after filtration indicated that adsorption and absorption processes were among the mechanisms involved in the removal processes. This study indicated that limestone can be used as an alternative to replace activated carbon.     

Basic characterization of Norwegian NOM samples — Similarities and differences

NOM (natural organic matter) samples, isolated by reverse osmosis (RO), and nine NOM samples, concentrated by low-pressure, low-temperature evaporation (EVA) from various origin in Norway, were characterized by different methods. The methods included elemental content of the freeze-dried samples (C, H, N, and O), elemental content of the redissolved samples (DOC, Na, Ca, Cu, Fe, and Mn), specific spectral absorbance at λ = 254 nm (A(254 nm)/DOC) and at λ = 436 nm (A(436 nm)/DOC), UV/Vis-spectra, specific fluorescence (excitation and emission spectra), proton capacity, Cu-complexation capacity, and content of hydrolysable amino acids and carbohydrates. In addition, chromatographic characterization by gel chromatography and reversed-phase chromatography was done. Studies on adsorption and flocculation abilities and the formation of trihalomethanes (THM) and organic halogens adsorbable on activated carbon (AOX) upon chlorination were also investigated. Comparison of the results showed that the samples were different according to the origin of the sample, isolation procedure, and time of sampling. The differences are not the same for all parameters used. Standardized procedures have to be applied to redissolve the organic material in water in order to compare data. For the samples investigated, it was shown that parameters like elemental analysis (H/C ratio), the specific spectral absorption in the UV range, proton capacity, complexation capacity and anionic particle charge, amount of hydrolysable amino acids and carbohydrates, adsorption behaviour on activated carbon, and the THM-FP are sensitive parameters to show differences concerning origin and isolation procedure.     

Potential use of solar energy for waste activated sludge treatment

The use of solar energy as a disintegration unit operation for waste activated sludge was tested in a pilot plant. The effect of the treatment process on chemical oxygen demand (COD), total suspended solids (TSS), settling time and filtration index was investigated in single (solar) and sequential processes (solar & biological). Solar oxidation was found to be a good sludge disintegration technology. Available solar photons were utilised to degrade the soluble organic matter and release the cell liquids. The highest COD and TSS removal efficiencies were obtained by the month of June. Sequential process efficiencies were related to accumulate solar photons, aerobic treatment time and operational condition. Sequential process resulted in COD and TSS removal efficiency of 16% and 13%, respectively. Increasing aerobic treatment time and/or mixing the oxidised sludge with fresh sludge improved COD and TSS removal efficiencies to 23% and 27%, respectively. The use of sequential processes improves the settling tendency of sludge by bio-oxidation of the released portions and eliminates protein charge effect on sludge settling.     

Removal of radionuclides at a waterworks

A waterworks with an average production rate of 1.3 m3 s(-1), providing several large cities in the province of Scania with drinking water has been studied regarding its capacity to remove several natural and anthropogenic radionuclides. The raw water is surface water from lake Bolmen which is transported through an 80 km long tunnel in the bedrock before it enters the waterworks. The method used for purification is a combination of coagulation-flocculation and filtration in sand filters. Two different purification lines are currently in use, one using Al2(SO4)3 as a coagulant and one using FeCl3. After coagulation and flocculation the precipitate is removed and the water is passed through two different sand filters (rapid filtration and slow filtration). Water samples were collected at the lake, the inlet to the waterworks, after each of the flocculation basins (Al2(SO4)3 and FeCl3), after rapid filtration and from the municipal distribution network. The samples were analysed with respect to their content of uranium, thorium, polonium, radium, plutonium and caesium. The results show a high removal capacity for uranium (about 85%), thorium (>90%), plutonium (>95%) and polonium (>90% in the coagulation-flocculation process) while caesium, strontium and radium pass through the purification process with almost unchanged activity concentrations. During transportation of the water in the tunnel it was also observed that infiltration of groundwater leads to a change in isotopic ratios and/or activity concentrations for the naturally occurring radionuclides and plutonium.     

Emission modelling and validation of VOCs' source strengths in air-conditioned office premises

An emission model for indoor volatile organic compounds (VOCs) based on mass balance considerations has been presented and validated under steady state conditions. Comparison were made for the measured and predicted concentrations of 37 selected VOCs and TVOC through a case intervention study on the filters of the ventilation system in a new commercial air-conditioned office building. The intervention involved replacing media filters with electronic and carbon filtration. TVOC and 37 compounds selected for their health and comfort impact, representation of major chemical classes that occur in indoor air and their utility as markers of pollution sources were studied. The concentration levels predicted by the model were compared with actual measurements. Twenty-five target compounds and the TVOC were adequately described by the model where the measured concentrations were in agreement with the predicted concentrations. Modeling of the remaining 12 compounds was found to be affected by the emission rates that were occupant related.     

Integrated and comprehensive estimation of greenhouse gas emissions from land systems

Exchanges of carbon and nitrogen between the atmosphere and terrestrial ecosystems involve a complex set of interactions affected by both natural and management processes. Understanding these processes is important for managing ecosystem productivity and sustainability. Management processes also affect the net outcome of exchanges of greenhouse gases between terrestrial ecosystems and the atmosphere. In developing a national carbon accounting system (NCAS) for Australia to account for emissions and removal of greenhouse gases to and from the atmosphere, a carbon:nitrogen mass balance ecosystem model (FullCAM) was developed. The FullCAM model is a hybrid of empirical and process modelling. The approach enables application to a wide range of natural resource management issues, because it is at land-management-relevant spatial and temporal resolution and captures the main process and management drivers. The scenario-prediction capability can be used to determine the emissions consequences of different management activities. Because, in Australia, emissions of greenhouse gases are closely related to the retention of dead organic matter and the availability of nitrogen for plant growth, the carbon and nitrogen cycling as modelled are good indicators of ecosystem productivity and condition. The NCAS also emphasizes the advantages of a comprehensive and integrated approach to developing a continental scale ecosystem-modelling system that has relevance both to estimation of greenhouse gas emissions and sustainable management of natural resources.     

水量衡算条件下人工湿地对有机物的去除

构建了芦苇和无植物人工湿地,在系统水量衡算的基础上比较了两种湿地对生活污水中有机物的去除效果。结果表明,在植物收割后的冬季,有植物湿地对有机物的去除率低于无植物湿地2.2%;在其他季节,芦苇湿地对污水CODCr的去除率比无植物的高出3.2%～4.2%,但对BOD5的去除率却比无植物的低了1.8%～3.4%。有植物湿地对有机物的去除效果比无植物湿地有所改善,但是提高不多。比较了两种系统的氧化还原电位,有植物湿地比无植物湿地高（P<0.05）,这种提高主要集中在湿地水面以下约15 cm的范围,从整体来看,两块湿地内部氧化还原状态大体相同,主要是强还原环境。比较了两块湿地基质中降解有机物的细菌、放线菌和真菌的数量,二者没有明显的差别,但是,有植物湿地的根际效应明显。考察了湿地进水有机负荷与去除量的关系,二者呈现显著的线性相关性(R2>0.96)。      

Environmental occurrence and risk of organic UV filters and stabilizers in multiple matrices in Norway

Eight organic UV filters and stabilizers were quantitatively determined in wastewater sludge and effluent, landfill leachate, sediments, and marine and freshwater biota. Crab, prawn and cod from Oslofjord, and perch, whitefish and burbot from Lake Mjøsa were selected in order to evaluate the potential for trophic accumulation. All of the cod livers analysed were contaminated with at least 1 UV filter, and a maximum concentration of almost 12 μg/g wet weight for octocrylene (OC) was measured in one individual. 80% of the cod livers contained OC, and approximately 50% of cod liver and prawn samples contained benzophenone (BP3). Lower concentrations and detection frequencies were observed in freshwater species and the data of most interest is the 4 individual whitefish that contained both BP3 and ethylhexylmethoxycinnamate (EHMC) with maximum concentrations of almost 200 ng/g wet weight. The data shows a difference in the loads of UV filters entering receiving water dependent on the extent of wastewater treatment. Primary screening alone is insufficient for the removal of selected UV filters (BP3, Padimate, EHMC, OC, UV-234, UV-327, UV-328, UV-329). Likely due in part to the hydrophobic nature of the majority of the UV filters studied, particulate loading and organic carbon content appear to be related to concentrations of UV filters in landfill leachate and an order of magnitude difference in these parameters correlates with an order of magnitude difference in the effluent concentrations of selected UV filters (Fig. 2). From the data, it is possible that under certain low flow conditions selected organic UV filters may pose a risk to surface waters but under the present conditions the risk is low, but some UV filters will potentially accumulate through the trophic food chain.     

Radiocarbon and stable carbon isotope compositions of chemically fractionated soil organic matter in a temperate-zone forest

To better understand the role of soil organic matter in terrestrial carbon cycle, carbon isotope compositions in soil samples from a temperate-zone forest were measured for bulk, acid-insoluble and base-insoluble organic matter fractions separated by a chemical fractionation method. The measurements also made it possible to estimate indirectly radiocarbon ((14)C) abundances of acid- and base-soluble organic matter fractions, through a mass balance of carbon among the fractions. The depth profiles of (14)C abundances showed that (1) bomb-derived (14)C has penetrated the first 16cm mineral soil at least; (2) Delta(14)C values of acid-soluble organic matter fraction are considerably higher than those of other fractions; and (3) a significant amount of the bomb-derived (14)C has been preserved as the base-soluble organic matter around litter-mineral soil boundary. In contrast, no or little bomb-derived (14)C was observed for the base-insoluble fraction in all sampling depths, indicating that this recalcitrant fraction, accounting for approximately 15% of total carbon in this temperate-zone forest soil, plays a role as a long-term sink in the carbon cycle. These results suggest that bulk soil organic matter cannot provide a representative indicator as a source or a sink of carbon in soil, particularly on annual to decadal timescales.     

Simulation of pollution buffering capacity of wetlands fringing the Lake Victoria

Lake Victoria has undergone substantial and most negative changes, especially over the last 30 years. One of the driving factors is nutrient enrichment from human activities in the catchment, which is causing eutrophication. This has been associated with, among others, the rapid proliferation of water hyacinth, alga blooms, and with general disruption of the lake ecosystem. Most of pollution to the lake flow via the natural wetlands. In order to understand how wetlands function within the Lake Victoria ecosystem a wetland model has been developed. The main objective of the model is to establish and simulate the buffering processes and capacity of individual wetlands (that is, their ability to absorb sediments, nutrients and pollutants) within the Lake Victoria basin. It was found that in both seasonal and permanent swamp there is a net export of organic matter produced in the wetlands. Most of the inorganic phosphorous were retained in the wetlands (60% to 90% removal) while there was a negative retention of nitrates probably due to the export of organic matter which associate very much with nitrates.     

Source apportionment of fine carbonaceous particles by positive matrix factorization at Gosan background site in East Asia

Fine particle (aerodynamic diameter <2.5 microm) samples were collected during six intensive measurement periods from November 2001 to August 2003 at Gosan, Jeju Island, Korea, which is one of the representative background sites in East Asia. Chemical composition of these aerosol samples including major ion components, trace elements, organic and elemental carbon (OC and EC), and particulate polycyclic aromatic hydrocarbons (PAHs) were analyzed to study the impact of long-range transport of anthropogenic aerosol. Aerosol chemical composition data were then analyzed using the positive matrix factorization (PMF) technique in order to identify the possible sources and estimate their contribution to particulate matter mass. Fourteen sources were then resolved including soil dust, fresh sea salt, transformed natural source, ammonium sulfate, ammonium nitrate, secondary organic carbon, diesel vehicle, gasoline vehicle, fuel oil combustion, biomass burning, coal combustion, municipal incineration, metallurgical emission source, and volcanic emission. The PMF analysis results of source contributions showed that the natural sources including soil dust, fresh and aged sea salt, and volcanic emission contributed to about 20% of the measured PM(2.5) mass. Other primary anthropogenic sources such as diesel and gasoline vehicle, coal and fuel oil combustion, biomass burning, municipal incineration, metallurgical source contributed about 34% of PM(2.5) mass. Especially, the secondary aerosol mainly involved with sulfate, nitrate, ammonium, and organic carbon contributed to about 39% of the PM(2.5) mass.     

Investigating soils retention ratios and modelling geochemical factors affecting heavy metals retention in soils in a tropical urban watershed

This study aimed at investigating the retention of Pb and Cd in soils and the geochemical factors influencing the adsorption of these pollutants. Soil samples were air-dried and ground to pass through a 2-mm sieve, and different soil extracts were prepared for chemical analysis (organic matter, cation exchange capacity and pH). Total Pb and Cd were extracted with diacid using digestion method and determined by atomic adsorption spectrophotometer (AAS) after filtration. Results revealed that the heavy metals retention ratio (RR) of the Rhodic ferralsol, Xanthic ferralsol and Mollic gleysol (2) were very high for Cd (>80 %) and was relatively low (generally < 60 %) for Pb. In contrast, RRs for the Plinthic gleysol and the Mollic gleysol (1) were relatively low (<60 %), regardless of the heavy metal concerned. Multiple regression equations indicated for Pb and Cd concentrations different linear relationships over simple linear regression, when pH, organic matter, clay percentage and cation exchange capacity (CEC) were used as independent variables. Results indicate that organic matter exerts major influences on the retention of Pb and Cd in soils, while CEC, clay content and pH have a minor influence in this process in the Ntem watershed. From these observations, the application of soil organic matter could be a solution in protecting shallow aquifers from heavy metal pollution and thus insuring that they are not a hazard to public health.     

Organic carbon changes in the surface sediments of the Venice lagoon

The concentrations of total, inorganic and organic carbon in the surface sediment of the central part of the Venice lagoon (31-55 stations) during the month of June in 1987, 1993 and 1998 were recorded. In two stations: San Giuliano and Lido, samples were collected on a monthly basis for 1 year also in different periods. On an average, by considering the whole central lagoon, inorganic carbon (IC) and total carbon (TC) did not show significant changes. In contrast organic carbon (OC) had alternating trends showing a decrease from 1987 to 1993, due to the almost complete disappearance of huge macroalgal biomasses, and a marked increase from 1993 to 1998, because of the high sediment disturbance caused by the catching of the clam Tapes philippinarum Adams & Reeve which had colonised the sediment free of macrophytes. The carbon changes monitored in the two stations studied on a seasonal basis during different years not only confirmed such results, but also enhanced the effects of fishing activities at Lido station and those depending on the disappearance of macroalgae at S. Giuliano. Moreover, this paper underlines the importance of seagrass beds. In fact in the areas colonised by those plants the percentage of fine sediments and organic matter is on the increase, while erosive processes are contrasted.     

Effectiveness of centralized bilge water treatment — a field study

Instrumentation and procedures were developed for gross and detailed characterization of oily wastewaters. The methodology was applied to the assessment of effectiveness of a centralized oily waste treatment facility. Generated data included total, dissolved, and suspended organic content and detailed chemical characteristics of oily water samples.The usefulness of the methodology was demonstrated in a real-life field study involving operation of a centralized oily waste treatment facility operated by the U.S. Army at Fort Eustis, Virginia, in 1976. It was found that the concentration of suspended organics ranged between 5 and 335 ppm and dissolved organics between 14 and 156 ppm in untreated bilge water.Treated bilge waste effluents contained essentially no suspended oil, but rather high (769–1262 ppm) amounts of dissolved organic matter.It was determined that physical methods of waste treatment based on gravity separation and coalescence are effective in removal of suspended petroleum, and that prolonged contact between an oil film and water results in water solubilization of petroleum, leading to very high concentrations of dissolved organic material in the treated effluent.     

A review of occurrences and treatment of polynuclear aromatic hydrocarbons in water

The scope of PAH contamination of raw, finished, and distributed waters is reviewed. The concentrations of PAHs in drinking water sources range from nanogram to microgram-per-liter quantities. Conventional treatment (flocculation, sedimentation, chlorination, and filtration) appears to substantially reduce total PAH concentrations present at higher concentrations in source waters. A major factor in this reduction is the removal of PAHs adsorbed onto particulate matter. The role of chlorination is not clear and reactions of PAHs with chlorine may in fact produce products which themselves are deleterious. Activated carbon can further assist in PAH removal. However, it may be inappropriate for treatment of PAHs present at low concentrations. Water entering the distribution system can become recontaminated via contact with reservoirs and pipes coated with coal-tar or asphalt based products.     

Phosphate removal by activated carbon–silica nanoparticles composite,kaolin, and olive cake

This work aimed to utilize four low-cost materials, namely activated carbon (AC), activated carbon–nanoparticle composite, kaolin, and olive cake, for phosphate removal. Batch mode tests were used to evaluate the performance of the adsorbents. The parameters affecting the adsorption process such as pH, initial concentration, mixing time, dosage, and temperature were studied. The obtained results showed that the removal efficiency of the adsorbents followed the order of: activated carbon–nanosilica > activated carbon > kaolin > olive cake. The addition of silica nanoparticles significantly enhanced the removal efficiency of activated carbon by 18.1% reaching a removal efficiency of 98% at 15wt% nanosilica loading. The adsorption isotherm data fitted well with Langmuir and Redlich–Peterson models with a correlation coefficient of >0.98, which indicates a monolayer homogenous adsorption. The fitness of the kinetic models was ranked as: pseudo-second-order > pseudo-first-order > intraparticle model. The calculated values of ΔH° = 23.4 kJ/mole, ΔS° = 0.11 kJ/mole, and ΔG = ?7.4 to ?11.8 kJ/mole indicated the endothermic and spontaneous nature of adsorption. The positive value of activation energy (17.66 kJ/mole) and the very low value of the sticking probability (2.4 × 10^?4) suggest high indefinite sticking of the phosphate ions to the adsorbent surface. The removal efficiency increased with time, dosage, and temperature, while it decreased with the increase in the initial concentration at an optimum pH of 7. The obtained results buttressed the benefit of using silica nanoparticles to enhance activated carbon capacity for phosphate removal, while kaolin and olive cake provided lower removal.     

鄱阳湖生态区长期施肥对稻田土壤碳汇效应与固碳潜力的影响

在施肥条件下确定平衡状态时,土壤有机碳含量水平对于正确评价土壤的固碳潜力和制定合理的有机物质分配措施具有重要意义。分析了前人研究的江西省有机碳储量数据并采用Jenny模型对长期不同施肥下有机碳动态数据进行模拟。结果表明,鄱阳湖生态区有机碳储量占全省的46%,以鹰潭地区最高,九江地区最低。施肥明显增强了土壤的碳汇作用,单施有机肥或有机无机肥配施（70F+30M、50F+50M、30F+70M、NPKM、NPK+S、NPK+P和NPK+C）处理的土壤有机碳含量明显高于施化肥处理,以南昌县的30F+70M、进贤县的NPKM和余江县的NPK+P处理最高,其平衡时有机碳含量和固碳潜力分别较施化肥处理提高了3061%和6115%、3017%和5496%、3826%和7479%。因此,提高鄱阳湖生态区农田有机碳密度和固碳潜力最有效方法是有机无机肥配施,其配施方式以猪粪配施化肥相对最好,配施比例以70%有机肥配施30%化肥为宜