TThe objective of the current study was to investigate the backwashing behavior of granular media filters used in water treatment under realistic conditions and to develop better models of the backwash process based on both fundamental and practical considerations. The focus of this study was on water only backwash but the applicability of the results to auxiliary backwash systems is discussed. The effects of filter backwash rate, coagulant used, degree of filter clogging and age of filter deposits on backwash behavior and efficiency were investigated in a pilot scale in-line filtration plant treating low turbidity raw water from a large dam. The results of these experiments and their implications both for modeling and managing filter backwash are discussed. The initial stages of backwashing are shown to be dominated by mixing and flow localization effects not accounted for in existing models of backwash. These effects appear to be dependent on both the equipment and the experimental conditions making the development of an accurate model of transient backwash behavior extremely difficult. However, it is shown that the overall efficiency of backwash can be predicted based on data about the filter and backwash design and operation that should be available at any treatment plant. This is an important first step in the development of modeling tool for the design and optimization of the complete filter cycle. A significant finding of this study was that the average age of filter deposits is one of the most important factors determining the ease with which they are detached during backwashing. Deposits become more difficult to remove the longer they remain in the filter. This has important implications for the robust design and operation of filters in applications where optimal backwash cannot be guaranteed. The rate of accumulation of mud in a filter over multiple filter cycles was determined experimentally for one set of backwash conditions and a procedure for estimating the useful life of a filter bed with sub-optimal backwash is proposed.

Esta pesquisa comparou a incorporação de iodeto de propídio (IP) com a avaliação simultânea de corantes indicativos de danificação em membrana e atividade enzimática (Live/Dead Cell Assay®) para a estimar a viabilidade de cistos de Giardia muris e oocistos de Cryptosporidium parvum. Além disso, foram testados métodos de recuperação de (oo)cistos em amostras de lodo e água de lavagem de filtros (ALF) geradas em escala de bancada, simulando tratamento de água por ciclo completo com decantação. Dentre os métodos estudados para a detecção de G. muris e C. parvum inoculados em amostras de lodo, destacou-se a floculação com sulfato férrico, seguida de separação imunomagnética (IMS). Realizou-se, portanto, ensaio de qualidade analítica com ColorSeedTM, para este método, tendo atendido ao requerido pelo Método 1623.1 da USEPA (2012) para Giardia spp. (32,25%; CV=9,00%), mas não tendo sido suficiente para Cryptostoridium spp. (11,00%; CV=47,67%). O teste com ColorSeedTM em amostras de ALF reproduziu o procedimento de filtração em membrana (FM) com raspagem utilizando Tween® 80 (45°C, 0,1%) seguido de IMS, tendo atendido ao Método 1623.1 para Giardia spp. (13,00%, CV=19,61%), mas não tendo sido suficiente para Cryptostoridium spp. (2,00%; CV=93,54%). Optou-se por este procedimento na avaliação de qualidade analítica, pois o inóculo prévio de suspensões comerciais seguido de recuperação por FM sem IMS superou 100% para C. parvum, devido à utilização de fator de multiplicação. O desempenho do Live/Dead Cell Assay® sobre suspensões comerciais de (oo)cistos foi subjetivo, sobretudo para visualização de organismos enzimaticamente ativos, de modo que optou-se pela inclusão de IP como parâmetro para estimar o efeito dos métodos de recuperação sobre a viabilidade. Em função da baixa recuperação e fluorescência de G. muris, a incorporação de IP foi avaliada apenas em C. parvum. Os resultados reiteraram a dificuldade na recuperação de protozoários em lodo e ALF e o fato de que as particularidades destes procedimentos analíticos podem prejudicar a interpretação de dados de viabilidade. / This study compared the incorporation of propidium iodide (PI) with the simultaneous evaluation of dyes that indicate both membrane damage and enzymatic activity (Live/Dead Cell Assay®) to assess the viability of Giardia muris cysts and Cryptosporidium parvum oocysts. In addition, methods of recovering protozoan cysts and oocysts from sludge and filter backwash water (FBW) samples generated on bench scale, simulating conventional water treatment with decantation, were tested. Among the studied methods for detection of G. muris and C. parvum spiked into sludge samples, ferric sulphate flocculation followed by immunomagnetic separation (IMS) lead to higher recoveries. An analytical quality assay was therefore carried out with ColorSeedTM having met the USEPA Method 1623.1 (2012) recommendation for Giardia spp. (32.25%, CV=9.00%) but not for Cryptostoridium spp. (11.00%, CV = 47.67%). The quality assay test for FBW samples replicated the membrane filtration (MF) procedure using Tween® 80 (45 °C, 0.1%) followed by IMS, having complied with Method 1623.1 for Giardia spp. (13.00%, CV=19.61%) but again not for Cryptostoridium spp. (2.00%; CV=93.54%). This procedure was chosen for the analytical quality exam, since the previous inoculum of commercial suspensions followed by MF without IMS exceeded 100% recovery for C. parvum, due to the use of a multiplication factor. The Live/Dead Cell Assay® performance on commercial suspensions of cysts and oocysts was subjective, especially for visualizing enzymatically active organisms, thus PI inclusion was chosen as the parameter to estimate the effect of recovery methods on the organisms\' viability. Due to the low recovery and poor fluorescence of G. muris, IP inclusion was evaluated only in C. parvum. The results reiterated the difficulty in the recovery of protozoa from sludge and FBW and the possibility of these analytical procedures hinder the interpretation of cysts and oocysts viability.

Bei der Aufbereitung von Rohwässern zu Trinkwasser fallen in der Regel unvermeidbare Rückstände an, die den gesetzlichen Bestimmungen entsprechend entsorgt werden müssen. Schlammhaltige Wässer, die den größten Anteil an Wasserwerksrückständen einnehmen, entstehen bei der Spülung von Filtern und enthalten nahezu alle aus dem Rohwasser entfernten Stoffe und nicht im Trinkwasser verbleibende Aufbereitungschemikalien. Während früher in vielen Wasserwerken Teile des schlammhaltigen Filterspülwassers nach einem Sedimentationsvorgang wieder in den Aufbereitungsprozess zurückgeführt wurden, ist dies in Deutschland auf Grund einer möglichen Beeinträchtigung der Trinkwasserqualität bei mikrobiologisch belasteten Wässern (z. B. Oberflächenwasser) ohne eine adäquate Behandlung (z. B. Ultrafiltration) nicht mehr erlaubt. Somit müssen schlammhaltige Filterspülwässer anderweitig entsorgt werden, z. B. durch eine Einleitung in die Kanalisation. Die dabei auftretenden Auswirkungen auf Abwasserbehandlungsanlagen sind noch nicht ausreichend bekannt. In der vorliegenden Arbeit werden unterschiedliche Ultrafiltrationsmodule (Kapillarmembranmodul und getauchtes Modul) hinsichtlich ihrer Eignung zur Aufbereitung aluminiumhaltiger schlammhaltiger Filterspülwässer und damit zur Rückführung des entstehenden Filtrates in den Aufbereitungsprozess untersucht. Die grundsätzliche Eignung beider Modulsysteme wird nachgewiesen. Bei Verwendung von getauchten Modulen kann auf eine vorangehende Sedimentationsanlage verzichtet werden. Als kritisch muss unabhängig vom gewählten Modulkonzept die Entsorgung des anfallenden Retentates angesehen werden, da die gesetzlich vorgeschriebenen Grenzwerte der Indirekteinleitung für mehrere Parameter nicht eingehalten werden. Bilanzierungen der relevanten Schadstoffe ergeben, dass der Schadstoffeintrag überwiegend diffus mit dem Rohwasser in das Wasserwerk erfolgt. Zur Untersuchung von Auswirkungen der Einleitung aluminiumhaltiger schlammhaltiger Filterspülwässer aus der Oberflächenwasseraufbereitung auf die Abwasserbehandlung wurden labortechnische Versuche zur Ermittlung des Phosphatadsorptionspotenzials durchgeführt. Neben der Abhängigkeit der Phosphatadsorptionskapazität vom pH-Wert wurde der Einfluss der Feststoffkonzentration des schlammhaltigen Filterspülwassers in Versuchen mit Modellwasser nachgewiesen. Eine Erhöhung der Feststoffkonzentration wirkt einer möglichst hohen Ausnutzung des Adsorptionspotenzials entgegen. Während für die Ultrafiltrationsbehandlung gegenüber der Indirekteinleitung ein Kostenvorteil ermittelt wird, ist die für die Nutzung des Phosphatadsorptionsanteils verfügbare Schlammmenge für einen alleinigen Einsatz in der Kläranlage bei gleichen Einzugsgebieten nicht ausreichend. / In most water treatment plants (WTPs), during the water purification process, residuals are generated that have to be disposed according to current regulations. Most of the residuals are derived from filter backwash processes (i. e. spent filter backwash water, SFBW) and contain substances that are removed from the raw water. In addition, in the spent filter backwash water, chemicals can be found that are required for the operation of the water treatment process and do not remain in the drinking water. Over recent decades, SFBW has been returned to the beginning of the water treatment plant (WTP) after a sedimentation process in order to reduce the amount of water being discharged. Concerns over the recycling of microorganisms, of heavy metals or precursors for disinfection by-products, have led to a significant reduction of the number of WTPs that directly return filter backwash water to the water treatment process. According to German technical standards, the reuse of SFBW might only be possible after the application of groundwater infiltration or an equivalent technique. Because of an almost complete recovery of particles and microorganisms, ultrafiltration treatment is a proven alternative to groundwater recharge of SFBW. In this work, different ultrafiltration modules for the treatment and reuse of SFBW are compared. Capillary as well as submerged membrane modules are suitable for the treatment of SFBW. If submerged membrane modules are used, no sedimentation period prior to ultrafiltration treatment is necessary. As a consequence of the accumulation of particulate matter including heavy metals and other compounds in the retentate during ultrafiltration treatment, threshold values of several regulations cannot be met, and either the discharge of retentate into the sewer will be charged or alternative disposal options must be considered. Mass balances for an entire WTP showed most of these contaminants to originate from non-point sources in the watershed. Lab-scale experiments are performed for the examination of the phosphate adsorption potential of SFBW derived from surface water treatment using aluminum-based coagulants. Besides a strong influence of the pH-value present in the SFBW, an influence of the TSS-concentration of SFBW on phosphate adsorption capacity could be demonstrated. Elevated TSS-concentrations resulted in a lower phosphate adsorption capacity of the investigated SFBW. While ultrafiltration treatment with subsequent reuse of SFBW might be cheaper than the discharge to the sewer system, the amount of SFBW required for a complete phosphate removal in the wastewater treatment plant is to large and therefore, no economic advantage of phosphate adsorption could be demonstrated

Bei der Aufbereitung von Rohwässern zu Trinkwasser fallen in der Regel unvermeidbare Rückstände an, die den gesetzlichen Bestimmungen entsprechend entsorgt werden müssen. Schlammhaltige Wässer, die den größten Anteil an Wasserwerksrückständen einnehmen, entstehen bei der Spülung von Filtern und enthalten nahezu alle aus dem Rohwasser entfernten Stoffe und nicht im Trinkwasser verbleibende Aufbereitungschemikalien. Während früher in vielen Wasserwerken Teile des schlammhaltigen Filterspülwassers nach einem Sedimentationsvorgang wieder in den Aufbereitungsprozess zurückgeführt wurden, ist dies in Deutschland auf Grund einer möglichen Beeinträchtigung der Trinkwasserqualität bei mikrobiologisch belasteten Wässern (z. B. Oberflächenwasser) ohne eine adäquate Behandlung (z. B. Ultrafiltration) nicht mehr erlaubt. Somit müssen schlammhaltige Filterspülwässer anderweitig entsorgt werden, z. B. durch eine Einleitung in die Kanalisation. Die dabei auftretenden Auswirkungen auf Abwasserbehandlungsanlagen sind noch nicht ausreichend bekannt. In der vorliegenden Arbeit werden unterschiedliche Ultrafiltrationsmodule (Kapillarmembranmodul und getauchtes Modul) hinsichtlich ihrer Eignung zur Aufbereitung aluminiumhaltiger schlammhaltiger Filterspülwässer und damit zur Rückführung des entstehenden Filtrates in den Aufbereitungsprozess untersucht. Die grundsätzliche Eignung beider Modulsysteme wird nachgewiesen. Bei Verwendung von getauchten Modulen kann auf eine vorangehende Sedimentationsanlage verzichtet werden. Als kritisch muss unabhängig vom gewählten Modulkonzept die Entsorgung des anfallenden Retentates angesehen werden, da die gesetzlich vorgeschriebenen Grenzwerte der Indirekteinleitung für mehrere Parameter nicht eingehalten werden. Bilanzierungen der relevanten Schadstoffe ergeben, dass der Schadstoffeintrag überwiegend diffus mit dem Rohwasser in das Wasserwerk erfolgt. Zur Untersuchung von Auswirkungen der Einleitung aluminiumhaltiger schlammhaltiger Filterspülwässer aus der Oberflächenwasseraufbereitung auf die Abwasserbehandlung wurden labortechnische Versuche zur Ermittlung des Phosphatadsorptionspotenzials durchgeführt. Neben der Abhängigkeit der Phosphatadsorptionskapazität vom pH-Wert wurde der Einfluss der Feststoffkonzentration des schlammhaltigen Filterspülwassers in Versuchen mit Modellwasser nachgewiesen. Eine Erhöhung der Feststoffkonzentration wirkt einer möglichst hohen Ausnutzung des Adsorptionspotenzials entgegen. Während für die Ultrafiltrationsbehandlung gegenüber der Indirekteinleitung ein Kostenvorteil ermittelt wird, ist die für die Nutzung des Phosphatadsorptionsanteils verfügbare Schlammmenge für einen alleinigen Einsatz in der Kläranlage bei gleichen Einzugsgebieten nicht ausreichend. / In most water treatment plants (WTPs), during the water purification process, residuals are generated that have to be disposed according to current regulations. Most of the residuals are derived from filter backwash processes (i. e. spent filter backwash water, SFBW) and contain substances that are removed from the raw water. In addition, in the spent filter backwash water, chemicals can be found that are required for the operation of the water treatment process and do not remain in the drinking water. Over recent decades, SFBW has been returned to the beginning of the water treatment plant (WTP) after a sedimentation process in order to reduce the amount of water being discharged. Concerns over the recycling of microorganisms, of heavy metals or precursors for disinfection by-products, have led to a significant reduction of the number of WTPs that directly return filter backwash water to the water treatment process. According to German technical standards, the reuse of SFBW might only be possible after the application of groundwater infiltration or an equivalent technique. Because of an almost complete recovery of particles and microorganisms, ultrafiltration treatment is a proven alternative to groundwater recharge of SFBW. In this work, different ultrafiltration modules for the treatment and reuse of SFBW are compared. Capillary as well as submerged membrane modules are suitable for the treatment of SFBW. If submerged membrane modules are used, no sedimentation period prior to ultrafiltration treatment is necessary. As a consequence of the accumulation of particulate matter including heavy metals and other compounds in the retentate during ultrafiltration treatment, threshold values of several regulations cannot be met, and either the discharge of retentate into the sewer will be charged or alternative disposal options must be considered. Mass balances for an entire WTP showed most of these contaminants to originate from non-point sources in the watershed. Lab-scale experiments are performed for the examination of the phosphate adsorption potential of SFBW derived from surface water treatment using aluminum-based coagulants. Besides a strong influence of the pH-value present in the SFBW, an influence of the TSS-concentration of SFBW on phosphate adsorption capacity could be demonstrated. Elevated TSS-concentrations resulted in a lower phosphate adsorption capacity of the investigated SFBW. While ultrafiltration treatment with subsequent reuse of SFBW might be cheaper than the discharge to the sewer system, the amount of SFBW required for a complete phosphate removal in the wastewater treatment plant is to large and therefore, no economic advantage of phosphate adsorption could be demonstrated