High Natural Organic Matter Content Research Articles

Determining Fe concentration and speciation in waters with high natural organic matter content

Valency, solubility and size of Fe are important controls on quality of natural waters. Recent recognition of the ubiquitous influence of natural organic matter on these, means that wider monitoring of Fe species in waters containing organic matter is required. We assess and develop methods that explicitly recognize this need. We show that for water samples prepared by acidification and filtration for inductively coupled plasma – atomic emission spectroscopy (I.C.P.-A.E.S.) analysis, only 50%–80% of Fe was recovered. This was because acidification coagulated the natural organic matter; Fe could then attach to its surface and/or be entrained as it deposited, both processes prevent Fe entering the I.C.P.-A.E.S. We show that this discrepancy in analysis of Fe – which could also occur and be more significant in analysis of trace metals - is likely to be undetected as the coagulate is unlikely to be observed prior to analysis. Accurate Fe analysis was possible, by I.C.P.-A.E.S. if H2O2 and U.V. light were used to remove organic carbon (O.C.), or by use of proprietary Fe chelators that produce colored complexes (e.g. Palintest LR, Palintest, UK). We also show that reliable resolution of Fe(II) concentration into free Fe(II) and Fe(II) bound to O.C. can be achieved by monitoring the time taken for ferrozine color development. This occurs within 2 s for free Fe(II) but up to 3 days for Fe(II) bound to O.C.

Development of a low-cost method for quantifying microplastics in soils and compost using near-infrared spectroscopy

Near-infrared (NIR) spectroscopy is a promising candidate for low-cost, nondestructive, and high-throughput mass quantification of microplastics in environmental samples. Widespread application of the technique is currently hampered mainly by the low sensitivity of NIR spectroscopy compared to thermoanalytical approaches commonly used for this type of analysis. This study shows how the application of NIR spectroscopy for mass quantification of microplastics can be extended to smaller analyte levels by combining it with a simple and rapid microplastic enrichment protocol. For this purpose, the widely used flotation of microplastics in a NaCl solution, accelerated by centrifugation, was chosen which allowed to remove up to 99% of the matrix at recovery rates of 83%–104%. The spectroscopic measurements took place directly on the stainless-steel filters used to collect the extracted particles to reduce sample handling to a minimum. Partial least squares regression models were used to identify and quantify the extracted microplastics in the mass range of 1–10 mg. The simple and fast extraction procedure was systematically optimized to meet the requirements for the quantification of microplastics from common polyethylene-, polypropylene-, and polystyrene-based packaging materials with a particle size <1 mm found in compost or soils with high natural organic matter content (>10% determined by loss on ignition). Microplastics could be detected in model samples at a mass fraction of 1 mg g−1. The detectable microplastic mass fraction is about an order of magnitude lower compared to previous studies using NIR spectroscopy without additional enrichment. To emphasize the cost-effectiveness of the method, it was implemented using some of the cheapest and most compact NIR spectrometers available.

Understanding the natural organic matter removal mechanism from mine and surface water through the electrocoagulation method

Abstract In the present study, the concept of ‘Sample alteration of surface water’ has been employed to improve the efficiency of the aluminum-based electrocoagulation (EC) treatment method for the removal of reactive fractions of natural organic matter (NOM) from chlorinated water. The characteristics of surface water have been slightly modified by adding mine water in different ratios. The process has been optimized using the response surface methodology (RSM) considering pH, current density, mix ratio, and contact time as factors. At the optimized condition, the EC method has significantly reduced total organic carbon, dissolved organic carbon (DOC), and UV254 absorbance values up to 24%, 27%, and 80%, respectively. The cumulative impact of sample alteration and EC method has exhibited outstanding coagulant activity in terms of UV254 abs, DOC, turbidity, phenol, and absorbance slope index (ASI) as well. A decrease in ASI values indicated the reduction of trihalomethane's formation in water-containing chlorine. This was validated by reduced chlorine demand. It can be concluded that mixing mine water with surface water can be a feasible and efficient method for treating water with a high NOM content.

The influence of surface waters on the bioavailability and toxicity of zinc oxide nanoparticles in freshwater mussels

The release of engineered nanoparticles in the aquatic environment could pose a threat to the biota. The purpose of the study was to examine the influence of surface water characteristics on zinc oxide nanoparticles (nZnO) and ZnS04 toxicity to the freshwater mussel Dreissena polymorpha. Mussels were exposed to an equivalent concentration of 25 μg/L Zn as either nZnO or ZnSO4 for 96 h at 15 °C in 4 types of surface waters: green water (high conductivity and pH with low natural organic matter content), brown water (low conductivity and pH with high natural organic matter content), diluted municipal effluent (high conductivity and pH with high urban organic matter content) and aquarium water (treated green water with organic matter removed). After the exposure period, mussels were analyzed for air-time survival, total and labile Zn levels in tissues, lipid metabolism (phospholipase A2, triglycerides levels) and oxidative stress (glutathione S-transferase, arachidonate cyclooxygenase, lipid peroxidation). The data revealed that mussels exposed to ZnSO4 in controlled aquarium water accumulated more total and labile Zn tissues, decreased oxidative stress and triglycerides and increased air time survival. While nZnO had few effects in aquarium water, oxidative stress was enhanced and total Zn in tissues were decreased in brown water and diluted municipal effluent and triglycerides were higher in nZn-exposed mussels in brown water. Air-time survival was decreased in mussels kept in green water and nZnO. It was also decreased in mussels exposed to ZnSO4 in green water and diluted municipal effluent. In conclusion, the fate and toxic effects of Zn could be influenced by both the chemical form (nanoparticles or ionic Zn) and surface water properties in freshwater mussels.

Pilot scale investigation of coagulation combined with ozonation and pH adjustment in treatment of NOM rich water

This paper presents the results of a pilot scale investigation of coagulation using aluminium based coagulants (polyaluminium chloride sulphate (PACL1) and polyaluminium chloride (PACL2)), combined with pre-ozonation and pH adjustment, on natural organic matter (NOM) removal from groundwater. Tests were conducted at a semi-industrial pilot plant, using groundwater with a high content of NOM (5.1 ± 0.8 mg C/L dissolved organic carbon (DOC); 0.211 ± 0.007 cm−1 UV absorbance at 254 nm (UV254)) and trihalomethane formation potential (THMFP (273 ± 73 μg/L)). It was determined that both coagulants showed similar efficacy in reducing DOC (∼50%), UV254 (∼60%) and THMFP (∼65%). Application of pre-ozonation enhanced total coagulation efficiency (up to 61% and 80% for DOC and UV254, respectively), probably due to its microflocculation effect. THMFP in the treated water fluctuated depending on ozone dose, coagulant type and pH. The pre-treatment resulted in NOM oxidation to lower molecular weight hydrophilic organic substances. PACL1 coagulation did not efficiently remove these new THM precursors, whereas PACL2 was able to reduce THMFP to 77 μg/L at a low ozone dose of 0.4 mg O3/mg DOC, suggesting differences in the coagulation mechanism for the two coagulants. This difference confirms the necessity of optimizing the combined treatment depending upon the choice of coagulant applied.

Trends on Natural Organic Matter in Drinking Water Sources and its Treatment

Natural organic matter (NOM) can be defined as a mixture of complex organic compounds that universally present in natural waters. High NOM content in water strongly impact the water quality and treatment in several ways (e.g. causing colour and odour, filter fouling and increase coagulant dose). Besides that, NOM also acts as the main precursor to disinfectant by products (DBPs) produce from the reaction of NOM and disinfectant during water treatment. DBPs are known to be carcinogenic to human and animals. The formation of DBPs is depending on NOM characteristics. Generally, NOM characteristics are differ according to the water sources. In order to understand NOM properties, NOM fractionation is required and therefore different approaches have been proposed for its characterization. Meanwhile several methods of treatment have been developed to remove or reduce the amount of NOM in drinking water sources to prevent DBPs formation. The aim of this paper is to review and discuss the properties and available treatment techniques for NOM.

MS2 removal from high NOM content surface water by coagulation ‐ ceramic microfiltration, for potable water production

AbstractMS2 bacteriophages removal from surface water, characterized by high natural organic matter (NOM) content, was investigated by inline coagulation/flocculation pretreatment followed by ceramic microfiltration (MF). MS2 and DOC removal increased with lower pH and higher coagulant dose. Lowering the coagulant pH from 6.5 to 5.5 for polyaluminum chloride (PACl), and to 5.0 for iron chloride (FeCl), respectively, along with doubling of the coagulant dose from 2 to 4 mg Al/L, and from 4 to 8 mg Fe/L, respectively, maximized the virus removal, resulting in more than six log unit reductions up to complete virus retention. However, high residual metal concentrations were found under such conditions. Comparison of conventional two‐stage coagulation pretreatment with simple inline coagulation did not show any significant performance differences. Both investigated coagulants showed virus inactivation about two log units after 60 min contact time, which is equivalent to a virus inactivation of 99%. This inactivation was only reversible to a small extend by chemical or physical floc destruction. The investigated process combination can comply with modern hygienic barrier standards. © 2011 American Institute of Chemical Engineers AIChE J, 2012

LC-ESI/MS/MS analysis with derivatization applied to polar disinfection by-products in water treatment

Chlorination and ozonation experiments under conditions close to drinking water treatment were carried out with two different tap waters with low DOC content and water from a bog lake with high natural organic matter content. THM formation was low and in the range of 10 μg/L. Derivatization with dinitrophenylhydrazine and HPLC/tandem mass spectrometry were applied to measure carbonyl DBPs by precursor ion scans at m/z 163 for aldehydes and at m/z 182 for dicarbonyls. Formaldehyde, acetaldehyde, glyoxal, and methylglyoxal were formed by chlorination and ozonation. Ozonation produced the highest levels of carbonyls, in particular in the tap water samples. A strategy for structure suggestion and identification of unknown compounds on the basis of collision-induced dissociation (CID) mass spectra (MS) is given. The resulting structures are carbonyls with additional hydroxy and carboxy groups and serve for choice or synthesis of standard compounds for further identification. The possibilities and limits of compound identification are discussed.

Characterization of Oxidation processes: ozonation and the AOP O3/H2O2

The influence of water quality parameters (dissolved organic matter and alkalinity) on the efficiency of the ozone/hydrogen peroxide (O3/H2O2) advanced oxidation process (AOP) relative to the corresponding conventional ozonation process was investigated. In natural waters with a high natural organic matter content (≥3 mg/L), O3 decomposition is controlled by radical‐type chain reactions. Thus, the overall OH radical oxidation capacity is nearly independent if conventional ozonation is replaced by O3/H2O2 AOP. In contrast, when the organic matter content in the natural water is low (≤1 mg/L), the addition of H2O2 considerably enhances the oxidation capacity by OH radicals. A constant ratio between the OH radical and O3 concentration (Rct) was found during both treatments, making it possible to predict the oxidation of micropollutants with O3 and OH radicals if the rate constants of both oxidants are known. The oxidation of atrazine during ozonation and the combined process O3/H2O2 could be accurately predicted in natural waters.