Performance Of Water Treatment Processes Research Articles

Optimization of roughing filtration unit for a handwashing wastewater recirculation point-of-use system.

A downward roughing filter unit consisting of silica sand as the filter medium was optimized for performance towards removal of turbidity and suspended solids from handwashing wastewater. Design-Expert software was employed to optimize media particle size, filter depth, and flowrate. Linear and quadratic models were found to best fit the responses of turbidity and suspended solids removal, respectively. Particle size and flow rate were the only parameters with significant effects on removal of turbidity and suspended solids. Optimal conditions were found to be media particle size 0.6 mm, filter depth 12 cm, and flow rate 0.3 Lmin-1, corresponding to removal efficiencies of 62 and 67% for turbidity and total suspended solids (TSS), respectively, as predicted by the model. Validation of model at optimal conditions resulted in turbidity and TSS removal of 55 and 53%, respectively. Additionally, removal efficiencies of the roughing filter towards apparent colour, true colour, biochemical oxygen demand (BOD5), and chemical oxygen demand (COD) from handwashing wastewater were 56, 20, 32, and 5%, respectively. Overall, although turbidity of filtered water was >50 NTU, the reduction achieved by roughing filtration is a significant step in enhancing the performance of water treatment processes downstream, including filtration and adsorption by slow sand filters and activated carbon, respectively.

Biodiversity of organisms inhabiting the water supply network of Wroclaw. Detection of pathogenic organisms constituting a threat for drinking water recipients

The objective of the article was to present the diversity of organisms inhabiting the water supply network with particular consideration of pathogenic organisms that can cause an epidemiological threat, with the application of high throughput sequencing (HTS). The study material was water sampled from 15 points in the water supply system. High species diversity of bacteria was evidenced, as well as the presence of microorganisms from genus Clostridium and family Enterobacteriaceae. No presence of bacteria Clostridium perfringens was recorded, which suggests proper performance of water treatment processes. Owing to advanced techniques of molecular biology, the article also presents species very similar to pathogenic bacteria the detection of which is not possible by means of standard water analysis (plate culture). Based on literature data and very high similarity of the genome of the bacteria to that of pathogenic bacteria, the species are considered to potentially show the same negative character towards the recipient, and cause a serious epidemiological threat. Therefore, the performed analyses show that classic methods of assessment of sanitary quality of water are not fully sufficient, and HTS analysis should be performed as an auxiliary tool to provide the complete image of the community in the existing network.

Removal of natural organic matter from water using chemically activated coffee husk

The presence of natural organic matter (NOM) in source water has posed many challenges for conventional water treatment facilities. Small organic acids, such as humic acid, present in NOM, have a high potential to influence the performance of water treatment processes. Uncontrolled application of agricultural chemicals leads to the simultaneous presence of toxic substances. In this work, batch adsorption experiments were conducted to examine the biosorption of HA onto chemically activated coffee husk. The biosorption process was studied as a function of operating conditions, such as contact time, pH of the solution, HA concentration, adsorbent dose and agitation speed parameters. Experimental results showed that the adsorption has an equilibrium time of 60 min with a maximum adsorption of 93.7%. The optimum pH for maximum HA adsorption was found to be 5.5, with a maximum adsorption of 94.3%. . As the dose of adsorbent increased from 1 to 25 g/L, the concentration of HA was observed to reduce from 10 to 1.67 mg/L which is below the WHO (World Health Organization) guideline value of 2 mg/L. The amount of HA adsorbed increased with increasing the initial adsorbent concentration from 0.5 to 20 mg/L. The adsorption kinetics well fitted the pseudo-second order model with the correlation coefficient R2 = 0.997 and Ks = 0.078. The experimental sorption equilibrium can be represented by the Langmuir isotherm (R2 = 0.998, SSE = 0.006). An average desorption capacity of 87.3% was observed. The study shows that chemically activated coffee husk can be a potential candidate to be used as a biosorbent in the removal of NOM from aqueous solutions.

Tracking changes in composition and amount of dissolved organic matter throughout drinking water treatment plants by comprehensive two-dimensional gas chromatography–quadrupole mass spectrometry

Dissolved organic matter (DOM) can affect the performance of water treatment processes and produce undesirable disinfection by-products during disinfection. Several studies have been undertaken on the structural characterization of DOM, but its fate during drinking water treatment processes is still not fully understood. In this work, the nontargeted screening method of comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC×GC-qMS) was used to reveal the detailed changes of different chemical classes of compounds in DOM during conventional and advanced drinking water treatment processes at three drinking water treatment plants in China. The results showed that when the dissolved organic carbon removal was low, shifts in the DOM composition could not be detected with the specific ultraviolet absorbance at 254nm, but the changes were clear in the three-dimensional fluorescence excitation-emission matrix or GC×GC-qMS analyses. Coagulation-sedimentation processes selectively removed 37–59% of the nitrogenous compounds, alcohols and aromatic hydrocarbons but increased the concentrations of halogen-containing compounds by 17–26% because of the contact time with chlorine in this step. Filtration was less efficient at removing DOM but preferentially removed 21–60% of the acids. However, other organic matter would be released from the filter (e.g., nitrogenous compounds, acids, and aromatic hydrocarbons). Biological activated carbon (BAC) treatment removed most of the compounds produced from ozonation, particularly ketones, alcohols, halogen-containing compounds and acids. However, it should be noted that certain highly polar or high molecular weight compounds not identified in this study might be released from the BAC bed. After the whole treatment processes, the concentrations of nitrogenous compounds, alcohols, alkenes, aromatic hydrocarbons and ketones were decreased more by the advanced treatment processes than by the conventional treatment processes. Alcohol and ketone removals were probably related to the reduction in protein-like materials. Alkane removal was probably related to the reduction in fulvic acid-like and humic acid-like materials.

Competitive adsorption of fluoride and natural organic matter onto activated alumina

ABSTRACTNatural organic matter (NOM) is a major water constituent that affects the performance of water treatment processes. Several studies have shown that NOM can be adsorbed on the surface of oxides and may compete with other ions. The overall goal of this study was essentially to investigate the competitive adsorption between fluoride and NOM on activated alumina (AA). For this purpose, a humic acid (HA) was used as a model compound for NOM. The interaction of NOM with fluoride, the simultaneous competitive adsorption, and the effect of preloading AA with NOM were investigated. The specific absorbance of HA was determined at 254 nm. Size-exclusion chromatography measurements confirmed the adsorption of aromatic fractions of NOM onto AA. The presence of HA in the system inhibited fluoride sorption onto AA and the removal yield using fresh AA decreased from 70.4 % to 51.0 % in the presence of HA. The decrease was more pronounced using AA preloaded with HA, reaching 37.7 %. The interference of coexisting ions and their effect on fluoride removal capacity were evaluated, showing a severe impact of the presence of phosphate on the removal capacity unlike nitrates and sulfates, which slightly improved the fluoride sorption.

REMOVAL OF NATURAL ORGANIC MATTER FROM AQUEOUS SOLUTIONS BY ELECTROCOAGULATION

Natural organic matter (NOM) affects some qualitative parameters of water such as color. In addition, it can deteriorate the performance of water treatment process including coagulation, adsorption, and membranes. NOM also reacts with chlorine in the chlorination process and may form disinfection by-products. The present study was carried out in laboratory-scale in a batch system using a cylinder shape reactor with effective volume of 2 l. The initial NOM concentrations during the study period were 10, 25, and 50 mg/l. After specific time intervals, samples were taken from the reactor and filtered. Finally, the NOM removal according to total organic carbon (TOC) content of the samples that were analyzed with a TOC analyzer. The results showed that the highest NOM removal efficiency for three initial concentrations 10, 25, and 50 mg/l were 91, 94, and 82%, respectively. These removal efficiencies were obtained at pH 7, contact time of 20 min, and electrical current of 0.1 A. The electrical energy consumption was 0.08, 0.06, and 0.03 kWh/m 3 , respectively. In this study, the application of electrocoagulation (EC) treatment method using combined Al and Fe electrode was examined to remove NOM from aqueous solution. Based on the obtained results, the EC can be used as an effective method for removing NOM from aqueous solution.

Characterization of low molecular weight dissolved natural organic matter along the treatment trait of a waterworks using Fourier transform ion cyclotron resonance mass spectrometry

Dissolved natural organic matter (DOM), particularly the low molecular weight DOM, can affect the performance of water treatment processes and serve as a main precursor of disinfection by-products (DBPs) during chlorination. In this study, electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) was used to characterize the low molecular weight DOM along the treatment trait of a conventional drinking water treatment plant. The ESI FT-ICR MS data showed that various C, H, O-only class species were the major components in the source water. According to the van Krevelen diagram analysis, lignin- and tannin-like compounds were the most abundant components. Within an isobaric group, the DOM molecules with a high degree of oxidation (high O/C value) were preferentially removed during coagulation, while those with low degree of oxidation were found to be more reactive toward chlorine. In addition, 357 one-chlorine containing products and 199 two-chlorine containing products formed during chlorination were detected in the chlorination effluent sample at a high confidence level. The chlorinated products can be arranged into series, suggesting that they were originated from C, H, O-only precursor compounds, which were in series related by the replacement of CH4 against oxygen. For the first time, this study explored the behavior of low molecular weight DOM along a drinking water treatment trait on the molecular level, and revealed the presence of abundant unknown chlorinated products, which are probably rich in carboxylic and phenolic groups, in drinking water.

Study on Transformation of Natural Organic Matter in Source Water during Chlorination and Its Chlorinated Products using Ultrahigh Resolution Mass Spectrometry

Natural organic matter (NOM) can affect the performance of water treatment processes, and serves as a main precursor for the formation of disinfection byproduct (DBPs) during chlorination. To minimize such undesirable effects, a better understanding of its structural information and reactivity toward chlorine is necessary. In this study, electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) was used to study the molecular composition of NOM in source water. More than four thousand NOM components were resolved in the sample. NOM molecules with a low degree of oxidation (low O/C ratio) were found to be more reactive toward chlorine than those with high O/C ratio. Totally, 659 one-chlorine containing products and 348 two-chlorine containing products were detected in the chlorinated sample at a high confidence level. The chlorinated products can be arranged into series, which indicate they were originated from precursor compounds in series related by the replacement of CH(4) against oxygen. Of the 1007 chlorine-containing products observed in this study, only 7 molecular formulas can be found in previous studies, showing the distinct difference from previous studies. This study explored the reactivity of NOM toward chlorine on a molecular level, which was previously explained on the level of whole mixtures or fractions of NOM, and the identified chlorinated products may contribute to our knowledge of the unknown total organic halide (TOX).

정수처리공정상 염소소독부산물형성에 미치는 오존의 영향

The effect of ozone on the formation and the removal of disinfection byproducts(DBPs) of chlorination process was studied to elucidate the performance of water treatment process. The samples of raw water, prechlorination process, and preozonation process were analyzed quantitatively according to the Standard Methods for the Examination of drinking water. As a result, most of total trihalomethanes(THMs) which were formed in prechlorine treatment process was not removed in the preozonation process. Most of haloacetic acids(HAAs), haloacetonitriles(HANs), and chloral hydrate(CH) was removed in sedimentation and biological activated carbon(BAC) filtration processes. However, DBPs were increased more or less by postchlorine step. In particular, the formation of THMs and HAAs depends on ozone more than chlorine, but, the formation of HANs and CH depends on chlorine more than ozone. The seasonal variation of DBPs concentration for the year needs to be investigated to study the temperature effect because DBPs strongly depend on temperature among various efficient factors.