Liquid Chromatography-organic Carbon Detection Research Articles

Assessment of water treatment processes: detailed organic matter characterisation and membrane fouling indices at the Loddon Water Treatment Plant, Victoria, Australia

Recent advances in membrane technology have led to its broad application, and reverse osmosis (RO) systems now represent the fastest growing segment of the desalination market. Its performance is hindered by membrane fouling. In this study pre-treatment methods to reduce RO fouling were investigated including flocculation, adsorption and ion exchange. Detailed organic characterisations were made in terms of florescence spectroscopy excitation emission matrix (EEM), UV254 absorbance and liquid chromatography-organic carbon detection (LCOCD). The different pre-treatment methods were assessed in terms of the fouling potential. This was quantified in terms of the modified fouling index measured using a dead-end cell micro-filtration (MF) unit. The existing pre-treatment of granular activated carbon (GAC) filter led to a good organic removal. Among the pre-treatment methods tested in the laboratory, purolite ion exchange/adsorption was found to be better than FeCl3 flocculation in terms of the amount as well as the wide range of organics removal. A pre-treatment of flocculation with Poly-ferric-silicate (PFSi) as flocculent gave a higher removal of organic matter compared to other pre-treatments tested. DOC was reduced from 11.5 to 4.25 mg/L, and it removed mostly the humic type substances.

New method for urea analysis in surface and tap waters with LC-OCD-OND (liquid chromatography–organic carbon detection–organic nitrogen detection)

Research Article| May 01 2011 New method for urea analysis in surface and tap waters with LC-OCD-OND (liquid chromatography–organic carbon detection–organic nitrogen detection) Stefan A. Huber; Stefan A. Huber 1DOC-LABOR, Eisenbahnstr. 6, 76229 Karlsruhe, Germany E-mail: doc@doc-labor.de Search for other works by this author on: This Site PubMed Google Scholar Andreas Balz; Andreas Balz 1DOC-LABOR, Eisenbahnstr. 6, 76229 Karlsruhe, Germany Search for other works by this author on: This Site PubMed Google Scholar Michael Abert Michael Abert 1DOC-LABOR, Eisenbahnstr. 6, 76229 Karlsruhe, Germany Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2011) 60 (3): 159–166. https://doi.org/10.2166/aqua.2011.016b Article history Received: April 12 2010 Accepted: November 26 2010 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation Stefan A. Huber, Andreas Balz, Michael Abert; New method for urea analysis in surface and tap waters with LC-OCD-OND (liquid chromatography–organic carbon detection–organic nitrogen detection). Journal of Water Supply: Research and Technology-Aqua 1 May 2011; 60 (3): 159–166. doi: https://doi.org/10.2166/aqua.2011.016b Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex A new method for urea detection in surface and tap waters using LC-OCD-OND was developed. It could be shown that urea, ammonia and nitrate could be separated chromatographically from each other and from NOM (natural organic matter). A direct quantification at its specific retention time is possible using custom-made detectors for nitrogen and for organic carbon. Further, urea can be detected indirectly as urea is transformed to ammonia after enzymatic hydrolysis with urease. After sufficient contact time for complete hydrolysis to ammonia (about 320 minutes) urea concentration can be calculated on the basis of the additional ammonia measured by LC-OCD-OND. The limit of detection of urea as mass was determined as 4 ppb for natural waters and 1 ppb for deionised waters. natural organic matter (NOM), organic carbon detection (OCD), organic nitrogen detection (OND), size-exclusion chromatography (SEC), urea This content is only available as a PDF. © IWA Publishing 2011 You do not currently have access to this content.

Pre-coagulation and ultrafiltration of effluent impaired surface water for phosphorus removal and fouling control

The process combination of in-line coagulation and subsequent membrane filtration is a suitable advanced treatment stage to achieve higher quality standards regarding pathogens and phosphorus in biologically treated wastewater prior to its discharge into sensitive water bodies. In this study a membrane pilot installation (capacity of 6 m3/h) was operated in dead-end configuration to investigate phosphorus removal and fouling behaviour depending on FeCl3 dosage. In parallel, effects of in-line coagulation on the filtration behaviour were investigated in lab-scale filtration experiments. The coagulation leads to the predominant reduction of dissolved organic macromolecular substances which are detected as biopolymer fraction by liquid chromatography-organic carbon detection. Besides the removal of dissolved organic molecules, the resulting filter cake plays a major role for the performance of ultrafiltration. In lab-scale filtration experiments the in-line coagulation results in positive effects on the filtration stability. In contrast, high coagulant doses lead to the loss of filtration performance during the pilot operation. The installed in-line coagulation, however, successfully reduced the orthophosphate concentration in permeate to values below 30 μgP/L when operated at a fixed molar ratio of FeCl3 concentration to influent PO4-P concentration of 6 (ßPO4-P-value).

Controlling submicron particle deposition in a side-stream membrane bioreactor: A theoretical hydrodynamic modelling approach incorporating energy consumption

Soluble microbial products (SMP) in the sludge water phase are regarded as the main foulant in MBRs. This study further developed an existing hydrodynamic model by incorporating energy consumption. The focus was on the cost-effectiveness of crossflow (CF) velocity in the control of submicron particle deposition. A sensitivity analysis showed that CF had the greatest impact on both particle backtransport and energy consumption. The other operational variables, i.e., dry solid content (DS), membrane tube dimension ( D and L) and temperature ( T) were generally less influential with respect to particle backtransport and energy consumption. Submicron particles were likely to deposit in side-stream MBRs, and the lowest backtransport velocity was found for particle radii around 0.1 μm and CF below 0.5 m/s. A particle size distribution (PSD) profile of MBR sludge showed a main peak at 40 μm and a second peak at 0.1–1 μm. The abundance of submicron particles at 2000 kDa was confirmed by a Liquid chromatography–Organic Carbon Detection (LC-OCD) analysis. The colloids responsible for the second peak in the PSD received high weighting factors (high filter cake formation potential) in the model optimization. In a lab-scale MBR, this critical crossflow velocity was between 0.75 and 1 m/s at 40 L/(m 2 h).

Natural organic matter (NOM) fouling of ultrafiltration membranes: fractionation of NOM in surface water and characterisation by LC-OCD

Natural organic matter (NOM) plays a significant role in fouling of ultrafiltration membranes in drinking water treatment processes. The aim of this study was to obtain a better understanding of the interactions between the fractional components of NOM and a hydrophilic PES/PVP hollow fiber ultrafiltration membrane (150–200 kDa). NOM was fractionated into hydrophobic, transphilic and hydrophilic acid fractions according to the XAD-8/4 resin method proposed by Aiken et al. [1]. UF filtration tests were performed with diluted NOM fractions (1.5 mg/l DOC) isolated from surface water (Lake Ijssel). From NOM fractionation results, Lake IJssel water comprised about 53–55% hydrophobic, 20–22% hydrophilic and 25% transphilic NOM acids. Filtration of three NOM fractions (hydrophobic, hydrophilic and transphilic) suggested that the fouling potential was in the order: hydrophilic > hydrophobic > transphilic. The reversibility of fouling due to the hydrophilic fraction was very poor, and decreased from ca. 50% in the first cycle to <30% after 6 cycles. LC-OCD (Liquid Chromatography-Organic Carbon Detection) analyses of UF feed and permeate showed almost no rejection of humic acids (20,000∼1,000 Da), IOW molecular weight acids (< 350 Da) or neutrals/amphiphilic compounds (<350 Da). The absence of a polysaccharide peak (Mw>20,000 Da) in the LC-OCD chromatogram of the UF permeate, suggested that polysaccharides (> 20,000 Da) were rejected by the UF membrane and may have contributed to fouling.

Evaluation of the performance of different chemicals for cleaning capillary membranes

Often the evaluation of the best chemical agent to be used in ultrafiltration (UF) and microfiltration (MF) membrane processes is a trial and error process usually derived from pilot plant experiments in half technical scale. This is expensive and time-consuming as the membranes have to be fouled again after the cleaning step. To overcome this problem, a single membrane capillary test unit for testing out-in capillaries was used. The major benefit is the possibility of investigating the performance of different cleaning agents at several capillaries, which were fouled comparably as they were taken out of the same module. Within this study 16 capillaries were cleaned with different cleaning agents of the categories oxidants, bases and acids, alone or in combination with each other at two different temperatures. After each cleaning step the cleaning solution was gathered and analysed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) on inorganic and Liquid Chromatography-Organic Carbon Detection (LC-OCD) on organic eluted foulants to evaluate how the foulants are affected by the different cleaning agents. Additionally, the permeability before and after each elution experiment was measured in order to determine the cleaning efficiency. Based on the results proposals for the use of specific cleaning agents for specific fouling substances are derived.

Towards a better characterisation and understanding of membrane fouling in water treatment

This paper presents two successful case studies where LC-OCD (Liquid Chromatography-Organic Carbon Detection) tool was used to characterise fouling material in membrane processes. It has been demonstrated that this technique combined with other analytical methods is a powerful tool to identify species responsible for fouling, understand membrane fouling mechanisms and therefore provide solutions to prevent or/and minimise fouling.

Natural organic matter removal by nanofiltration: effects of solution chemistry on retention of low molar mass acids versus bulk organic matter

The main emphasis of this study is the difference in behaviour between low molar mass (LMM) acids and bulk natural organics such as humic substances and natural organic matter. Stirred cell experiments were used to investigate charge and size effects in the rejection behaviour of bulk natural organics as well as LMM acids by nanofiltration membranes. To distinguish between size and charge effects thorough characterisation of membrane, natural organics and ionic environment was carried out. Membrane zeta potential was determined as a function of the ionic environment and the intrinsic membrane rejection was measured with dextran, ionic solutions and synthetic surface water. The behaviour of three thin film composite (TFC), and one cellulose acetate (CA) membranes was studied as a function of solution chemistry (pH, ionic composition and strength, calcium concentration, and organic type). Rejections of DOC, UV 254 nm , as well as the cations calcium and sodium were measured. Natural organics in selected feed and permeate samples were also characterised using liquid chromatography organic carbon detection (LC-OCD) which allows the characterisation of the organic fractions in the low concentration permeates and hence give insight into the rejection of low molar mass (LMM) organics. The retention of such LMM compounds is important due to their impact on the microbiological regrowth potential of the product water. The results emphasised that charge and size are both important for cations and low molar mass acids. While the bulk of the natural organics are retained due to size exclusion that is independent on solution chemistry for the membranes investigated, the retention of LMM acids follows different mechanisms. The analysis of organic fraction in the permeates showed that the rejection of low molar mass acids is strongly pH, and thus charge, dependent while this effect of solution chemistry on the LMM acids was masked when only bulk organic rejection was measured.