{"id":16570,"date":"2026-08-05T16:25:24","date_gmt":"2026-08-05T14:25:24","guid":{"rendered":"https:\/\/www.proefschriftmaken.nl\/portfolio\/rinnert-schurer\/"},"modified":"2026-08-05T16:25:33","modified_gmt":"2026-08-05T14:25:33","slug":"rinnert-schurer","status":"publish","type":"us_portfolio","link":"https:\/\/www.proefschriftmaken.nl\/en\/portfolio\/rinnert-schurer\/","title":{"rendered":"Rinnert Schurer"},"content":{"rendered":"","protected":true},"excerpt":{"rendered":"","protected":true},"author":7,"featured_media":16571,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"us_portfolio_category":[45],"class_list":["post-16570","us_portfolio","type-us_portfolio","status-publish","post-password-required","hentry","us_portfolio_category-new-template"],"acf":{"naam_van_het_proefschift":"THE SIGNIFICANCE OF HIGH-MOLECULAR WEIGHT ORGANIC CARBON FOR THE BIOLOGICAL STABILITY OF DRINKING WATER","samenvatting":"Dit proefschrift onderzocht het belang van de organische koolstoffractie met een hoog molecuulgewicht (high-MW OC) in drinkwater voor de biologische stabiliteit, de neiging tot biofouling en hergroei van Aeromonas en het heterotroof plaatgetal (HPC). Dit werd onderzocht in desinfectiemiddel-vrij drinkwater dat met directe conventionele zuivering werd geproduceerd uit eutroof oppervlaktewater. High-MW OC wordt hier gedefinieerd als collo\u00efdale en deeltjesvormige biopolymere organische verbindingen met een molecuulgewicht van \u2265 10 kDa (kiloDalton), waaronder polysacchariden, eiwitten, DNA en microbi\u00eble biomassa. De aanleiding voor dit onderzoek was de waarneming van verhoogde concentraties Aeromonas in tapwatermonsters in verschillende drinkwaterdistributiesystemen in het zuidwesten van Nederland nadat de chlorering van het distributienetwerk begin jaren 2000 was be\u00ebindigd.\n\nHet onderzoek toonde aan dat de concentratie high-MW OC in drinkwater equivalent kan worden gekwantificeerd met twee methoden: PHMOC en LC-OCD. De verwijdering van high-MW OC door conventionele zuivering bleek onvolledig en seizoensafhankelijk. De veldstudie liet sterke correlaties zien tussen de concentraties high-MW OC, het totale microbi\u00eble groeipotentieel (BPP-assay) en biologisch afbreekbare biopolymeren (AOC-A3). Hergroei in het distributienet bleek sterker be\u00efnvloed te worden door langzaam biologisch afbreekbare high-MW OC-verbindingen dan door gemakkelijk afbreekbare verbindingen (AOC-P17\/NOX).\n\nEen belangrijk onderdeel van het onderzoek was de beoordeling van ultrafiltratie (UF) als nazuivering. Implementatie van 150 kDa UF in een full-scale systeem leidde tot een verlaging van high-MW OC van 65 naar 30 \u00b5g\/L, wat resulteerde in een aanzienlijke afname van HPC-getallen en Aeromonas-concentraties. Hoewel de biologische stabiliteit verbeterde, werd de streefwaarde voor Aeromonas nog niet volledig gehaald. Dit wijst erop dat voor volledige biologische stabiliteit mogelijk high-MW OC-niveaus onder de 10 \u00b5g\/L nodig zijn. Aanbevolen parameters voor monitoring zijn onder meer high-MW OC, totaal groeipotentieel, biofoulingpotentieel, ijzer in het water en de aanwezigheid van ongewervelden. Geavanceerde technieken zoals nanofiltratie en omgekeerde osmose bieden een robuust alternatief voor conventionele zuivering, omdat ze ook organische microverontreinigingen zoals PFAS effectief verwijderen.","summary":"This thesis investigated the significance of the high-molecular weight organic carbon fraction (high-MW OC) in drinking water for the biological stability, biofouling propensity and regrowth as Aeromonas and heterotrophic plate count (HPC) in disinfectant-free drinking water which has been produced with direct conventional treatment from eutrophic (reservoir) surface water. High-MW OC is defined here as the colloidal and particulate biopolymeric organic compounds with a molecular weight of \u2265 10 kDa (kilo Dalton) comprising polysaccharides, proteins, DNA, and microbial biomass. The driver for this investigation was the observation of increased levels in the tap water samples of the Dutch regulatory technical indicator parameter for regrowth Aeromonas (in some instances exceeding the target level of \u2264 1,000 colony-forming units (CFU) per 100 mL) in several drinking water distribution systems (DWDS) in the southwestern Netherlands after distribution chlorination had been terminated in the early 2000s (Chapters 1 and 3). This signaled the occurrence of biologically unstable conditions in the distributed water, which might eventually evolve into water quality issues such as customer complaints and occurrence of (opportunistic) pathogens. The Aeromonas regrowth persisted despite the levels of easily assimilable organic carbon (AOC-P17\/NOX), which had hitherto been considered as the traditional indicator parameter for biological stability, being appropriately low. The involved drinking water production facilities encompassed the typical succession of coagulation \u2013 sedimentation \u2013 rapid media filtration \u2013 UV (ultraviolet) or ozone disinfection \u2013 BACF (biological activated carbon) filtration. The assessment of ultrafiltration (UF) posttreatment to improve biological stability by reducing the concentrations of high-MW OC in the treated and distributed water was a major aspect of the investigation. The study deployed a suite of then recently available methods for the quantification in drinking water of high-MW OC (as well as its preliminary chemical characterization) with PHMOC (particulate and high-molecular weight organic carbon) and LC-OCD (liquid chromatography \u2013 organic carbon detection), total suspended microbial growth potential (BPP: biomass production potential assay), biodegradable biopolymers (AOC-A3: assimilable organic carbon for the A3 pure bacterial culture), biofouling potential for biomass (BAR: biomass accumulation rate) and iron (FeAR: iron accumulation rate), DWDS network fouling as loose deposits and pipe wall biofilm, and presence of invertebrates with flushing, swabbing followed by chemical and hydrobiological analyses.\n\nThe concentration of high-MW OC in drinking water was demonstrated to be equivalently quantifiable with two available methods namely particulate and high-MW OC (PHMOC; concentration with crossflow ultrafiltration) and as the LC-OCD (liquid chromatography \u2013 organic carbon detection) (Chapter 2). Both methods were suitable for application in biological stability studies. High-MW OC concentrations in the investigated conventionally treated surface waters were typically in the 50 \u2013 150 \u00b5g\/L range, i.e., only a few percent of the total organic carbon (TOC) content of 1.8 \u2013 2.3 mg\/L. High-MW OC removal from ~200 \u2013 500 \u00b5g\/L in the raw (reservoir) water by direct conventional treatment was incomplete and seasonally variable, reflecting temperature-dependent efficacies of the coagulation\/filtration and biological activity in BACF (Chapters 2, 3, 5 and 7). The high-MW OC most likely originated from algae in the raw water based on their concomitant seasonal maximum levels (Chapter 5), the ~50% polysaccharides and 10% proteins make-up of the high-MW OC (Chapter 3), and the seasonal variability of the treated water high-MW OC (Chapter 5), thereby supporting that the high-MW OC fraction comprises slowly biodegradable, biopolymeric compounds.\n\nHigh-MW OC, growth potential and regrowth in full-scale DWDSs\nThe field study of three treatment plants and their DWDSs (Chapters 3 and 5) showed strong correlations between the high-MW OC concentrations, the total suspended growth potential (BPP assay) and biodegradable biopolymers (AOC-A3) across the treatment lines. Moreover, on an average basis these parameters (measured in the BACF filtrate of the three plants) showed a positive correlation with regrowth in the DWDSs as Aeromonas, HPC, coliforms and large invertebrates. Mostly similar results were encountered in the full-scale trial of UF posttreatment (Chapter 6). In contrast, regrowth was absent in a DWDS supplied with dune-infiltration treated water where high-MW OC concentrations were \u2264 10 \u00b5g\/L. For AOC-P17\/NOX no correlation was observed with any of the suspended growth potential or regrowth parameters. Hence, the field data point to regrowth being impacted more by slowly biodegradable, high-MW OC compounds in the treated water than by easily biodegradable compounds.\n\nHigh-MW OC and growth potential\nThe impact of the presence of high-MW OC on suspended growth potential was verified under controlled conditions (Chapters 4, 5 and 6). Addition of indigenous high-MW OC (PHMOC concentrates from BACF-filtrate) increased the total growth potential and biodegradable biopolymers but not AOC-P17\/NOX. Ultrafiltration of BACF filtrate with membranes of 10 kDa, 150 kDa and 0.12 \u00b5m pore size lowered the high-MW OC concentration by ~ 75%, 70% and 35%, respectively (other OC fractions were not removed). Concomitant reductions in total growth potential with 20% \u2013 75% and biodegradable biopolymers (AOC-A3) with 90% (AOC-P17\/NOX was not reduced) were similar for all pore sizes, showing that the growth potential associated with the UF-retainable high-MW OC fraction rejectable resided in the > 0.12 \u00b5m subfraction. The stable or slowly increasing biomass concentrations during the BPP incubations were typical for a slowly biodegradable OC matrix, where consumptions in the order of magnitude of ten micrograms-per-litre suffice for the maintenance of comparatively high stationary biomass levels (rather than biomass growth). Overall, slowly biodegradable high-MW OC contributed to the suspended growth potential of drinking water. However, a significant portion of the total grow potential in the drinking water was thus attributable to (slowly biodegradable) compounds that were not retainable with UF (Chapter 6, 7).\n\nLowering high-MW OC, biofouling and regrowth with UF posttreatment\nThe potential of 150 kDa UF posttreatment to improve biological stability in terms of lowering growth potential, biofouling (loose deposits and pipe wall biofilm), invertebrates and Aeromonas and HPC regrowth by lowering high-MW OC from 65 to 30 \u00b5g\/L in the treated water was investigated in a full-scale DWDS (Chapter 6). For the April \u2013 October period of highest water temperature and maximum regrowth levels, median HPC numbers were reduced by 73% or more to \u2264 25 CFU\/mL (no exceedance of the regulatory standard) and median Aeromonas numbers declined by 60% \u2013 80% to \u2264 470 CFU\/100 mL, corresponding to exceedance of the technical standard being lowered from 25% to 8% (year-round basis). The levels of high-MW OC, growth potential and biofouling potential in the freshly produced UF permeate were lowered by the UF treatment to below or near the literature guideline values to avoid Aeromonas and HPC regrowth. However, growth potential and biofouling potential increased markedly in the downstream DWDS as the result of the concomitant increased presence of iron to the ~7 \u00b5g\/L concentration range.\n\nUF implementation resulted in 50% lower amounts of loose deposits and pipe wall biofilm in the DWDS, which contained most of the total organic carbon, active biomass, iron and Aeromonas in the DWDS. Importantly, these two niches are responsible for regrowth related water quality issues like brown water, opportunistic pathogens and invertebrate abundancy as presented in literature. However, the large invertebrate Asellus aquaticus, which other studies have linked to Aeromonas regrowth, remained abundant in the DWDS. Overall, while the improved biological stability was most likely attributable to the lowered high-MW OC concentration, the remaining Aeromonas exceedance, biofouling potential and growth potential, and A. aquaticus presence showed that biological stability had not yet been attained at the desired level, and high-MW OC levels below 10 \u00b5g\/L may be needed based on the absence of Aeromonas regrowth in DWDSs supplied with dune-infiltration treated water.\n\nRecommendations and outlook\nRecommended parameters for the monitoring of biological stability comprise high-MW OC (LC-OCD and PHMOC), total growth potential (BPP assay), biofouling potential (biofilm monitors), bulk water iron, network fouling (loose deposits and pipe wall characterization) and invertebrate presence (Chapter 6). The respective and combined contributions to biofouling, growth potential, regrowth and invertebrate presence of the high-MW OC fraction not retainable with 150 kDa UF treatment, of the OC fractions of lower MW, and of iron need further study. The presence, origin, and avoidance of iron and large invertebrates in the DWDS warrant specific attention with respect to attaining biological stability. Treatment options for the progressive removal of high-MW OC and other biodegradable organic carbon compounds of lower MW include tighter (< 10 kDa) UF membranes, slow sand filtration, nanofiltration and reverse osmosis. Importantly, the latter two technologies also lower the concentrations in drinking water of organic micropollutants including perfluoro-alkyl compounds (PFAS), which are increasingly emerging as being of toxicological and environmental concern. Nanofiltration and reverse osmosis therefore provide a synergistic and robust alternative to conventional treatment technologies, and will likely see wider application in the production of drinking water from surface water in the near future (Chapters 7 and 8).","auteur":"Rinnert Schurer","auteur_slug":"rinnert-schurer","publicatiedatum":"17 september 2026","taal":"EN","url_flipbook":"https:\/\/ebook.proefschriftmaken.nl\/ebook\/rinnertschurer?iframe=true","url_download_pdf":"https:\/\/ebook.proefschriftmaken.nl\/download\/e2399307-6ce1-415d-8c6b-81907535c083\/optimized","url_epub":"","ordernummer":"19273","isbn":"","doi_nummer":"","naam_universiteit":"Wageningen University","afbeeldingen":16572,"naam_student:":"","binnenwerk":"","universiteit":"Wageningen University","cover":"","afwerking":"","cover_afwerking":"","design":""},"_links":{"self":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/16570","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio"}],"about":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/types\/us_portfolio"}],"author":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/comments?post=16570"}],"version-history":[{"count":1,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/16570\/revisions"}],"predecessor-version":[{"id":16573,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio\/16570\/revisions\/16573"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media\/16571"}],"wp:attachment":[{"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/media?parent=16570"}],"wp:term":[{"taxonomy":"us_portfolio_category","embeddable":true,"href":"https:\/\/www.proefschriftmaken.nl\/en\/wp-json\/wp\/v2\/us_portfolio_category?post=16570"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}