Dissolved organic nitrogen removal during water treatment by aluminum sulfate and cationic polymer coagulation

Coagulation of three surface waters was conducted with aluminum salt and/or cationic polymer to assess dissolved organic nitrogen (DON) removal. Coagulation with aluminum sulfate removed equal or slightly lower amounts of DON as compared to dissolved organic carbon (DOC). At aluminum sulfate dosages up to 5 mg per mg DOC, the cationic polymer improved DON removal by an additional 15% to 20% over aluminum sulfate alone. At very high aluminum sulfate dosages (>8 mg aluminum sulfate per mg DOC), however, the cationic polymer addition negligibly increased DON removal. Molecular weight fractionation before and after coagulation experiments indicated that cationic polymer addition can increase the removal of all molecular weight fractions of DON with the highest molecular weight fraction (>10,000 Da) being preferentially removed. Results indicated that the DON added as part of the cationic polymer was almost completely removed at optimum aluminum sulfate and polymer doses.     

A review of technologies for the removal of sulfate from drinking water

Because of the current water crisis worldwide, it is of great importance to find alternative sources of drinking water, such as sulfur water. This review analyses laboratory, pilot and industrial-scale technologies available for sulfate removal from water produced for human consumption, from naturally occurring sulfur water and that resulting from human activities. Most of them exceed 90% removal efficiencies. However, the concentrations treated in each study were different; some technologies evaluate concentrations below recommended limits (250 mg L⁻¹), while others evaluate much higher concentrations but require previous treatments. The technologies with higher energy requirements such as reverse osmosis and ion exchange have better removal efficiencies but require larger initial investments and have higher operational costs. Biological treatments, on the other hand, with lower energy and material requirements, are less expensive but require long retention times and depend on the season of the year and/or environmental conditions. Lastly, adsorption removal technologies fall in the middle, especially for energy requirements and operational costs and retention times. This review shows that although there are a variety of sulfate removal technologies suitable for use, there is still room for a novel methodology that removes sulfates from a wider range of concentrations more economically, more effectively and in less time than what is currently available.     

Enhanced arsenite removal from water by Ti(SO4)2 coagulation

Coagulation with the conventional coagulants such as ferric and aluminum salts is not efficient for As(III) removal. In this study Ti(SO₄)₂ was employed for enhanced As(III) removal and Fe₂(SO₄)₃ was used as a reference. The removal efficiencies of As(III) by Ti(SO₄)₂ at pH 4.0–9.0 were greater than that by Fe₂(SO₄)₃ by 7.39–32.8% and 3.14–48.1% for coagulants dosed at 8.0 mg/L and 12.0 mg/L, respectively. The advantage of Ti(SO₄)₂ over Fe₂(SO₄)₃ for As(III) removal was more significant at lower pH, which may be ascribed to the more negatively charged surface of Ti(IV) hydroxides. To reduce As(III) from 0.2 mg/L to 10 μg/L, the necessary dosage of Ti(SO₄)₂ was only ～50% of that of Fe₂(SO₄)₃. The adsorption capacity of As(III) on Ti(IV) hydroxides formed in-situ was greater than that on Fe(III) hydroxides formed in-situ by ～100 mg/g and several times higher than the adsorption capacities of TiO₂ for As(III) reported in the literature. The presence of competing anions, silicate, phosphate and humic acid, did not alter the advantage of Ti(SO₄)₂ over Fe₂(SO₄)₃ for arsenite removal. Replacing partial Ti(SO₄)₂ with Fe₂(SO₄)₃ (same dosage) and applying them sequentially could achieve similar As(III) removal efficiency as single Ti(SO₄)₂, which could thus reduce the chemical cost. The extended X-ray absorption fine structure (EXAFS) spectroscopy indicated that As(III) form bidentate binuclear surface complexes with Ti(IV) hydroxides as evidenced by As(III)-Ti bond distances of 3.33–3.35 Å. This study revealed that Ti(SO₄)₂ may be an alternative coagulant for efficient As(III) removal.     

Organic polyelectrolytes in water treatment

The use of polymers in the production of drinking water is reviewed, with emphasis on the nature of the impurities to be removed, the mechanisms of coagulation and flocculation, and the types of polymers commonly available. There is a focus on polymers for primary coagulation, their use as coagulant aids, in the recycling of filter backwash waters, and in sludge thickening. Practicalities of polymer use are discussed, with particular attention to polymer toxicity, and the presence of residual polymer in the final drinking water. The questions of polymer degradation and the formation of disinfection by-products are also addressed.     

Submicron capsules extracted from rapeseed as novel flocculant agents for the treatment of turbid water

Flocculation is an important step in water treatment as it is responsible for the separation of suspended solids and colloids. The currently used flocculants have certain limitations with respect to environmental impact and disposal as well as potentially being harmful to human health, which has encouraged the study of natural flocculants originating from oleaginous plants. Oil-bodies are individual small organelles in which oleaginous seeds store triacylglycerols reserves. In this article, the flocculant properties of oil-bodies have been investigated. Oil-bodies flocculate at pH 5, 7 and 9 and high ionic strength (100 mM NaCl) and it was demonstrated that their intact structure is necessary for the flocculation activity as treatment with protease K and diethyl ether, that remove the protein coat and the oil-core, respectively, dramatically decreased the flocculation activity. This study shows that oil-bodies have the potential to be novel, natural, sustainable, environmentally friendly and biodegradable flocculant candidates for water treatment.     

硫酸铵在净水工艺中的应用

在原水氨氮含量较低的条件下,采用硫酸铵代替液氨投加在原水中,与氯消毒剂作用形成化合氯消毒,可达到净水工艺要求。硫酸铵的使用提高了系统的安全可靠性,避免了气体泄漏爆炸的危险。     

硫酸铵在净水消毒工艺中的应用

针对液氨在运输及使用过程中存在的安全隐患问题,采用硫酸铵作为加氨剂,考察了其应用在净水工艺中的可行性,并制定了液体硫酸铵的投加标准和要求.结果表明,液体硫酸铵能替代液氨达到净水工艺的要求,同时可消除水厂在氨瓶的运输、使用和存储过程中的氨气泄露风险.     

Virus inactivation by silver doped titanium dioxide nanoparticles for drinking water treatment

Photocatalytic inactivation of viruses and other microorganisms is a promising technology that has been increasingly utilized in recent years. In this study, photocatalytic silver doped titanium dioxide nanoparticles (nAg/TiO₂) were investigated for their capability of inactivating Bacteriophage MS2 in aqueous media. Nano-sized Ag deposits were formed on two commercial TiO₂ nanopowders using a photochemical reduction method. The MS2 inactivation kinetics of nAg/TiO₂ was compared to the base TiO₂ material and silver ions leached from the catalyst. The inactivation rate of MS2 was enhanced by more than 5 fold depending on the base TiO₂ material, and the inactivation efficiency increased with increasing silver content. The increased production of hydroxyl free radicals was found to be responsible for the enhanced viral inactivation.     

贵州村镇供水工程净水技术的选择

分析了贵州村镇供水工程现状及特点,并结合我省供水工程运行经验,提出适用于贵州村镇的净水技术,有利于保障居民饮用水安全、提高供水水质、降低供水成本,保证供水工程能取得良好的社会、经济、环境效益。     

Comparative study of humic acids flocculation with chitosan hydrochloride and chitosan glutamate

Flocculation of dissolved humic acids (HA) and their complexes with metal ions and organic pollutants is a crucial step in drinking water preparation due to significant undesirable effects of humic compounds on water quality. Constant demand for cheap, effective and environmentally friendly flocculants brings about the interest to natural cationic polymers which can be used to neutralize negative charge of humic colloids through polyelectrolyte complexes (PEC) formation. In this work, the interaction of HA with two types of soluble chitosan salts (hydrochloride and glutamate) at different pH and polymer ratios was studied with a focus on electrical charge of PEC formed and effectiveness of color removal in the flocculation process. For both chitosan forms flocculation window was found at pH close to the PEC isoelectric point (pI) in a wide concentration range; however, lower flocculant dose was required when chitosan glutamate was used.     

矿井水中硫酸根去除效果试验研究

针对山西省煤矿矿井水的水质特性,研究通过混凝吸附作用对矿井水中硫酸根的去除效果,通过实验,发现在pH=7～8时,采用Ca（OH）2＋PAC＋少量PAM的药剂投加方式,对矿井水中硫酸根的混凝吸附去除效果较好。     

硫酸盐还原菌在硫酸盐废水处理中的应用

介绍了硫酸盐废水来源、硫酸盐还原菌（SRB）的分类、生理特性及代谢方式,阐述了SRB处理硫酸盐废水的机理,概括了国内外利用SRB处理重金属废水、高浓度硫酸盐有机废水的应用现状,对SRB处理硫酸盐废水的技术前景进行了展望。     

Experimental investigation of a PV solar generator for supplying water treatment process

The paper describes a photovoltaic solar generator to supply a dielectric barrier discharge ozone generator employed for water treatment. This paper reports trials of the equipment and modelling the solar power generation system’s efficiency. The design methodology was used to obtain the optimal set point for the orientation of the solar panel during the passage of clouds which causes the decrease of sunlight and thus reduced ozone production. In Algeria, autumn is characterized by the passage of clouds almost every day which negatively affects the performance of the solar panel. The objective of this paper is to identify the set point and to set the robustness of the process in cloudy weather, by determining the optimal values of the orientation angles (north-south and east-west), in order to maximize the power produced by the solar system. Three ‘centred face-composite’ designs were performed on a laboratory experimental set-up and an optimal point was determined.     

Treatment of cotton textile wastewater using lime and ferrous sulfate

This technical note summarizes the results of a textile wastewater treatment process aiming at the destruction of the wastewater's color by means of coagulation/flocculation techniques using ferrous sulfate and/or lime. All the experiments were run in a pilot plant that simulated an actual industrial wastewater treatment plant. Treatment with lime alone proved to be very effective in removing the color (70-90%) and part of the COD (50-60%) from the textile wastewater. Moreover, the treatment with ferrous sulfate regulating the pH in the range 9.0+/-0.5 using lime was equally effective. Finally, the treatment with lime in the presence of increasing doses of ferrous sulfate was tested successfully, however; it proved to be very costly mainly due to the massive production of solids that precipitated.     

Dispersion of C60 in natural water and removal by conventional drinking water treatment processes

The first objective of this study is to examine the fate of C₆₀ under two disposal scenarios through which pristine C₆₀ is introduced to water containing natural organic matter (NOM). A method based on liquid-liquid extraction and HPLC to quantify nC₆₀ in water containing NOM was also developed. When pristine C₆₀ was added to water either in the form of dry C₆₀ or in organic solvent, it formed water stable aggregates with characteristics similar to nC₆₀ prepared by other methods reported in the literature. The second objective of this study is to examine the fate of the nC₆₀ in water treatment processes, which are the first line of defense against ingestion from potable water - a potential route for direct human consumption. Results obtained from jar tests suggested that these colloidal aggregates of C₆₀ were efficiently removed by a series of alum coagulation, flocculation, sedimentation and filtration processes, while the efficiency of removal dependent on various parameters such as pH, alkalinity, NOM contents and coagulant dosage. Colloidal aggregates of functionalized C₆₀ could be well removed by the conventional water treatment processes but with lesser efficiency compared to those made of pristine C₆₀.     

红泥塑料沼气工程在水葫芦治理上的中试研究——古田县水口镇朝天桥红泥塑料水葫芦处理示范沼气工程

本文介绍了新型三段式红泥塑料沼气工程工艺,该工艺对古田县水口镇朝天桥村的水葫芦进行了厌氧消化中试研究。研究结果发现,该沼气工程年处理水葫芦超过540吨,经过厌氧消化后年产沼气1.08万立方米,沼液460.8吨和沼渣57.6吨。其中沼液和沼渣用于周边农田、林地、果园和鱼塘施肥,获得了良好的环境、社会和经济效益。采用红泥塑料厌氧工艺,可以解决福建省乃至全国水葫芦污染和能源化利用问题。     

A regulatory robust conditional approach to measuring the efficiency of wholesale water supply and wastewater treatment services

A benchmarking evaluation instrument was designed with a European Union country regulatory authority for water supply and wastewater treatment services to determine the efficient operating cost of its service providers that operated in the wholesale market segment in the 2017–2021 period. To this end, the non-parametric Data Envelopment Analysis technique was adapted to a robust and conditional approach. The results point to similar mean efficiency scores between water supply and wastewater services in the five-year period, despite the greater heterogeneity in the latter. Furthermore, the estimated potential cost savings for both services ranged from about 2% to 3%.     

Membrane coagulation bioreactor (MCBR) for drinking water treatment

In this paper, a novel submerged ultrafiltration (UF) membrane coagulation bioreactor (MCBR) process was evaluated for drinking water treatment at a hydraulic retention time (HRT) as short as 0.5h. The MCBR performed well not only in the elimination of particulates and microorganisms, but also in almost complete nitrification and phosphate removal. As compared to membrane bioreactor (MBR), MCBR achieved much higher removal efficiencies of organic matter in terms of total organic carbon (TOC), permanganate index (COD(Mn)), dissolved organic carbon (DOC) and UV absorbance at 254nm (UV(254)), as well as corresponding trihalomethanes formation potential (THMFP) and haloacetic acids formation potential (HAAFP), due to polyaluminium chloride (PACl) coagulation in the bioreactor. However, the reduction of biodegradable dissolved organic carbon (BDOC) and assimilable organic carbon (AOC) by MCBR was only 8.2% and 10.1% higher than that by MBR, indicating that biodegradable organic matter (BOM) was mainly removed through biodegradation. On the other hand, the trans-membrane pressure (TMP) of MCBR developed much lower than that of MBR, which implies that coagulation in the bioreactor could mitigate membrane fouling. It was also identified that the removal of organic matter was accomplished through the combination of three unit effects: rejection by UF, biodegradation by microorganism and coagulation by PACl. During filtration operation, a fouling layer was formed on the membranes surface of both MCBR and MBR, which functioned as a second membrane for further separating organic matter.     

An autopsy study of a fouled reverse osmosis membrane element used in a brackish water treatment plant

The fouling of a spiral wound reverse osmosis (RO) membrane after nearly 1 year of service in a brackish water treatment plant was investigated using optical and electron microscopic methods, Fourier transform infrared spectroscopy (FTIR) and inductively coupled plasma atomic emission spectrometry (ICP-AES). Both the top surface and the cross-section of the fouled membrane were analysed to monitor the development of the fouling layer. It has been found that the extent of fouling was uneven across the membrane surface with regions underneath or in the vicinity of the strands of the feed spacer being more severely affected. Fouling appeared to have developed through different stages. In particular, it consisted of an initial thin fouling layer of an amorphous matrix with embedded particulate matter. The amorphous matrix comprised organic-Al-P complexes and the particulate matter was mostly aluminium silicates. Subsequently, as the fouling layer reached a thickness of about 5-7microm, further amorphous material, which is suggested to include extracellular polymeric substances such as polysaccharides, started to deposit on top of the existing fouling layer. This secondary amorphous material did not seem to contain any particulate matter nor any inorganic elements within it, but acted as a substrate upon which aluminium silicate crystals grew exclusively in the absence of other foulants, including natural organic matter (NOM).     

Solar disinfection (SODIS): simulation of solar radiation for global assessment and application for point-of-use water treatment in Haiti

Haiti and other developing countries do not have sufficient meteorological data to evaluate if they meet the solar disinfection (SODIS) threshold of 3-5 h of solar radiation above 500 W/m2, which is required for adequate microbial inactivation in drinking water. We have developed a mathematical model based on satellite-derived daily total energies to simulate monthly mean, minimum, and maximum 5-h averaged peak solar radiation intensities. This model can be used to assess if SODIS technology would be applicable anywhere in the world. Field measurements were made in Haiti during January 2001 to evaluate the model and test SODIS efficacy as a point-of-use treatment option. Using the total energy from a measured solar radiation intensity profile, the model recreated the intensity profile with 99% agreement. NASA satellite data were then used to simulate the mean, minimum, and maximum 5-h averaged peak intensities for Haiti in January, which were within 98.5%, 62.5%, and 86.0% agreement with the measured values, respectively. Most of the discrepancy was attributed to the heterogeneous nature of Haiti's terrain and the spatial resolution of the NASA data. Additional model simulations suggest that SODIS should be effective year-round in Haiti. Actual SODIS efficacy in January was tested by the inactivation of total coliform, E. coli, and H2S-producing bacteria. Exposure period proved critical. One-day exposure achieved complete bacterial inactivation 52% of the time, while a 2-day exposure period achieved complete microbial inactivation 100% of the time. A practical way of providing people with cold water every morning that has undergone a 2-day exposure would be to rotate three groups of bottles every morning, so two groups are out in the sun and one is being used for consumption.