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Drinking water treatment plants automation becomes more sophisticated, more on-line monitoring systems become available and integration of modeling environments with control systems becomes easier. This gives possibilities for model-based optimization. In operation of drinking water treatment plants, the processes are usually optimized individually on the basis of "rules of thumb" and operator knowledge and experience. However, changes in operational conditions of individual processes can affect subsequent processes and an optimal operation, which can include a number of water quality parameters, costs and environmental impact is different for every operator. Improvement of the operation of a drinking water treatment plant is possible by using an integrated model of the entire water treatment plant as an instrument for operational support and for process control. For this purpose, it is important that explicit objectives are defined for the operation. From the research it is concluded that the objective for integrated optimization of the operation of drinking water treatment should be the improvement of water quality and not a priori reduction of environmental impact or costs. In the research an integrated model for ozonation, including ozone decay, bromate formation, assimilable organic carbon (AOC) formation, E. coli disinfection, CT and decrease in UV absorbance at 254 nm (UVA254) is developed. With the model, different control strategies for ozonation are assessed. The research also describes a newly developed design for ozone installations, the dissolved ozone plug flow reactor, (DOPFR) and the effect of character and removal of natural organic matter (NOM) prior to ozonation. The research was carried out as part of the project Promicit, a cooperation of Waternet, Delft University of Technology, DHV B.V. and ABB B.V. and was subsidized by SenterNovem, agency of the Dutch Ministry of Economic Affairs. Part of the experiments was performed in cooperation with Kiwa Water Research.

In the water distribution network water quality process take place influenced by de flow velocity and residence time of the water in the network. In order to understand how the water quality changes in the water distribution network, a good understanding of hydraulics is required. Specifically in the periphery of the network, where customers are connected, the hydraulics can change rapidly. During the night time the water is almost stagnant and the residence time increases. In the morning, when everybody gets up and flushes the toilet and takes a shower, high flow velocities can occur. During the remainder of the day flow velocities are low. The stochastic model SIMDEUM was developed to simulate water use in small time scales (1 s) and small spatial scales (per fixture). The model SIMDEUM and its applications in several hydraulic and water quality models in water distribution networks were tested against measurements within these networks. SIMDEUM enables a good model of flow velocities, residence times and the connected water quality processes in the water distribution network.

The wastewater system in the Netherlands comprises approximately 100,000 km of sewer pipes and more than 350 wastewater treatment plants (wwtp). The system collects and treats the majority of domestic and industrial wastewater. A small amount of untreated wastewater, however, is occasionally discharged to rivers and lakes, often resulting in a deterioration of surface water quality. Responsible authorities (water boards and municipalities) attempt to reduce these discharges to abide by new European regulations. In the search for effective measures knowledge is required on the principle in-sewer processes. Knowledge on hydrodynamics is readily available; knowledge on water quality processes is as yet insufficient. This dissertation considers two novel monitoring techniques that can be applied in sewer systems and that measure water quality parameters. The first technique (UV/VIS spectroscopy) has been applied to study the wastewater arriving at the wwtp in Eindhoven. Results show a large variation in the amount of pollutants originating from the sewer system and arriving at the treatment plant. Especially during large storm events after a long dry period (the occurrence of which might increase according to climate change scenarios) an extreme amount of pollutants can cause a disruption of wwtp operation. The second technique (fiber-optic DTS) measures wastewater temperatures along a sewer section. It has been successfully applied to locate illicit connections in a stormwater system. The application in combined sewer systems allows a detailed study of any process that influences in-sewer temperatures such as discharges of wastewater from house-connections and the inflow of stormwater run-off.

This research deals with tertiary treatment techniques used for the removal of phosphorus from wastewater treatment plant (WWTP) effluent. The main objective of this research is to obtain ultra low total phosphorus (<0.15 mg total phosphorus/L) concentrations by coagulation, flocculation and filtration of wastewater treatment plant effluent. Knowledge of the different phosphorus forms in WWTP effluent is essential to reach ultra low concentrations in the WWTP effluent. The TU Delft phosphorus distribution has been developed to have an easy and quick method to determine orthophosphorus, metal-bound phosphorus, dissolved “organic” phosphorus and particulate organic phosphorus. The phosphorus distributions make it possible to compare the phosphorus removal of different filter concepts but it can also be used to compare different settings, for example flocculation time, initial mixing energy and filtration rates. Pilot-plant investigations were conducted at the Horstermeer WWTP and the Leiden Zuidwest WWTP. Results showed that the initial mixing energy has no influence on the phosphorus size fractionation and phosphorus distribution in the upper water layer of a fixed bed filter. This means that the initial mixing energy of 300 s-1 is already sufficient. During the filtration experiments, results showed that an increasing total phosphorus concentration in the feed water results in increased total phosphorus concentrations in the filtrate water. The coagulant dosage is a major influence on the filter runtime. With increasing coagulant dosage, the filter runtime decreases. For continuous sand filtration, an increase in the total phosphorus concentration in the feed water does not lead to higher total phosphorus concentrations in the filtrate water. 1-STEP® filtration reaches higher removal efficiencies compared to dual media filtration. It is to be concluded that phosphorus removal to an ultra low concentration can be achieved, but knowledge about the different phosphorus forms and their behaviour is of major importance.

Arsenic contamination of shallow tube well drinking water is an urgent health problem in Bangladesh. Current arsenic mitigation solutions, including (household) arsenic removal options, do not always provide a sustainable alternative for safe drinking water. A novel technology, Subsurface Arsenic Removal, relies on the existing technology of Subsurface Iron Removal. The principle of this technology is that aerated water is periodically injected into an anoxic or anaerobic aquifer through a tube well. The injection water partially displaces the original iron and arsenic containing groundwater. The oxygen-rich injection water oxidized adsorbed iron on the soil grains around the tube well. Once the flow direction is reversed, the oxidized iron (precipitated as iron (oxy)hydroxides) provides adsorption sites for soluble iron and arsenic. Subsequently groundwater with reduced iron and arsenic concentrations can be abstracted. This technology has the potential to be an affordable, robust and chemical-free arsenic removal solution for decentralized application. In this PhD study a combination field and laboratory research, in Bangladesh and the Netherlands, has resulted in better understanding of the subsurface processes determining the sustainable operation in diverse geochemical settings.

Ultrafiltration (UF) is a proven technology in water treatment nowadays. However, fouling remains a major challenge in the operation of UF, especially in regard to colloidal NOM fouling. In general, a number of colloidal NOM fouling mechanisms may occur, such as adsorption, gel formation. Colloidal NOM fouling is influenced by multivalent cations, ionic strength and pH. In order to control membrane fouling, different pretreatments such as powder activated carbon adsorption, lime softening, ion exchange, conventional media filtration and coagulation with inorganic and polymeric coagulant have been investigated. In-line coagulation is the most commonly used pretreatment for UF of surface water. However, the problem with in-line coagulation is that a large amount of backwash-derived waste sludge containing dosed coagulants is produced. Since the backwash waste sludge with coagulant has to be treated before its discharge (in especially Western Europe), this option creates additional cost for the membrane treatment plant (up to 20% of the total cost of the whole plant). This dissertation investigates the technical possibility of controlling the UF fouling by backwashing with low ionic strength water (demineralized water in the Netherlands), in order to reduce the ionic strength and the amount of multivalent cations and thus reduce NOM fouling. Chapter 1 briefly introduces this dissertation. The effectiveness of deminerlaized water backwashing is generally investigated on a pilot scale (with a 2.4m2 membrane) in Chapter 2. Results show that regarding the removal of NOM foulants via hydraulic backwashes, demineralized water is better than UF and NF permeate. That is probably due to the absence of cations, reducing the charge screening effect and/or Ca-bridging effect between the negatively charged membrane and NOM, leading to a restoration of repulsion force and consequently an easy removal of fouling layer. However, it is not clear which components in backwash water lead to the low foulant removal in this chapter. Therefore, Chapter 3 investigates the influence of backwash water composition on fouling control. Different amount of CaCl2 and NaCl was dosed in demineralized water to test their effect on fouling control. It became clear that the presence of monovalent and divalent cations in backwash water reduces the fouling control efficiency. Moreover, by isolating the organic matter in UF permeate for backwashing, it is found that the organic matter in UF permeate itself does not cause fouling problems when they are in backwash water. In terms of the influence of monovalent and divalent cations, both the elimination of the charge screening effect and the breakdown of the calcium bridging effect are possible mechanisms to explain this improvement. Therefore, these two effects are presumed to be the mechanisms of demineralized water backwashing. The investigation of the hypotheses of demineralized water backwashing is reported in Chapter 4, including the charge screening and the calcium bridging effects. By determining the zeta potential of the membranes and the colloidal NOM compounds at different conditions, the impact of pH and electrolyte valence and concentration on their charge was assessed. Furthermore, the adsorption of calcium on the membranes and the NOM compounds was also illustrated. Results showed that a membrane became less negatively charged when the pH decreased and the concentration of electrolyte increased, proving the presence of the charge screening effect. Furthermore, divalent cation has a much stronger effect on the increase of membrane zeta potential than monovalent cations which is generally in consistent with the DLVO theory. Calcium ions indeed adsorbed on either new or fouled membranes, and bridged NOM and membranes afterwards. However, the interaction of calcium with fouled membranes is more substantial than with new membranes. However, the charge screening effect played a dominant role in the membrane fouling and fouling control by demineralized water backwashing. Most of the fouling caused by calcium bridging is difficult to remove even with a demineralized water backwash. Chapter 5 illustrates the effectiveness of demineralized water backwashing on ultrafiltration fouling of different fractions of NOM. Results of natural waters show the same fouling removal via demineralized water backwashing as the previous chapters. Furthermore, LC-OCD analysis of Schie Canal water showed that biopolymers can be flushed away by hydraulic backwashes of either demineralized water or UF permeate. Compared to almost zero removal of humics and LMW substances by UF permeate backwashes, demineralized water backwashing was able to remove a substantial amount of humics, and a small amount of LMW substances. Fouling of sodium alginate model compound showed a high reversibility no matter what kind of backwash water was used. This is also consistent with the LC-OCD analysis of Schie Canal water. However, not all biopolymers were removed by hydraulic backwashes. A low fouling reversibility was observed for BSA fouling, but BSA may be in the part of unremoved biopolymers with demineralized water. No improvement in fouling control for fouling of Suwannee River humic acid (SRHA) was observed as well when demineralized water was used for the backwash. This is probably because the calcium bridging via carboxyl functional groups is the main mechanism for SRHA fouling, which is difficult to break down. Since the charge screening effect is the main mechanism of demineralized water backwashing, theoretically speaking, its application on seawater treatment is also possible. Chapter 6 demonstrates that demineralized water backwashing can substantially improve seawater UF fouling control, similar to the previous findings in surface canal water. However, the duration of a successful demineralized water backwash should be extended from one to two minutes. This is due to the high salinity of seawater and thus more demineralized water was required to dilute the seawater and limit a higher dispersion effect of seawater than surface water. Monovalent cations in backwash water showed their impact on the fouling control efficiency, indicating the existence of a charge screening effect. Furthermore, the different UF membrane fouling behaviors in winter and spring indicated the impact of a seasonal influence on UF membrane fouling. In spring, the membrane showed more fouling probably due to the algae bloom which is widely considered an important fouling factor. The results of the long-term experiment reconfirmed the effectiveness of backwashing with SWRO permeate (similar quality as demineralized water) on the fouling control of seawater UF. Since it is very easy to access SWRO permeate in a UF-RO desalination plant, this approach can be implemented easily. In order to apply this technique in industry, optimization work was conducted on a pilot scale with a standard membrane element (40 m2) and reported in Chapter 7. Results show that SWRO permeate (having similar qualities as demineralized water) backwashing substantially improved the seawater UF fouling control, consistent with the previous studies with small-scale membrane modules. The effectiveness of SWRO permeate backwashing on UF fouling control was observed at a recovery rate up to 95.8% during a low fouling period. Furthermore, the results of the DEMIFLUSH pilot were similar to the Evides desalination plant having the same operational settings, suggesting that the results obtained from the DEMIFLUSH pilot are applicable to full-scale plants. However, the results of high fouling period are missing. If the optimization results can be repeated in high fouling period as well, the application of SWRO permeate is also economically feasible due to the low consumption of SWRO permeate. Optimization work should be continued to reduce the consumption of SWRO permeate or demineralized water, since the usage of these water is expensive.

The objective of this research is to limit the risks of fully automated operation of drinking water treatment plants and to improve their operation by using an integrated system of process models and emulated process automation software. This thesis contains the design of such an integrated system. The use of the system is investigated in the three identified applications, i) optimization of process control, ii) training of operation supervisors and iii) virtual commissioning of process automation software.

Ethanol production, as a renewable energy source and fuel additive, form starch based grains such as corn and wheat has increased rapidly in recent years to mitigate green-house gas emissions due to the extensive usage of fossil fuels and to regulate the instabilities in global fuel supply (Gao et al., 2011, Wilkie et al., 2000). However, bio-ethanol manufacturing is a water and energy intensive process that generates a high amount of concentrated wastewater called stillage and requires a high amount of energy input for downstream stillage management with centrifuges, evaporators and dryers. Therefore, its overall environmental benefit is still questionable. The only by-product of bio-ethanol production facilities is called dry distillers grains with solubles (DDGS) and it is produced through a series of energy intensive processes for concentrating the effluent coming from the main distillation process. DDGS, rich with proteins, carbohydrates, lipids and nutrients, has a high nutritional value and it is valorized in animal feed market to compensate the operation costs and to improve the overall feasibility of the process (Eskicioglu et al., 2011).

Congresbundel ‘De Watercyclus; daar zit wat in!’ van de 65ste Vakantiecursus Drinkwater en Afvalwater (VC2013), gehouden op 11 januari 2013 te Delft. Uitgave van de Sectie Sanitary Engineering van de Faculteit Civiele Techniek en Geowetenschappen van de TU Delft.

The objective of this research was to decrease membrane fouling of a ceramic microfiltration system and at the same time increase the recovery. A conventional operation in micro- and ultrafiltration is an in-line coagulation and a frequent hydraulic backwash. The idea about these frequent backwashes is to limit the accumulation of fouling on the membrane. But the cake layer of iron or alum flocks can also protect the membrane for pore blocking and a frequent backwash can expose the membrane for particles that cause pore blocking. The frequent backwash is also using a lot of permeate. In this way the net flux is lower than the actual flux and the recovery can be as low as 60 to 70%. In this research it was hypothesized that this cake layer worked as a membrane protecting layer and was accumulating on the top of membrane by long filtration backwash intervals (>6 hours). Also a layer of powdered activated carbon was put on the membrane at the start of a filtration cycle (pre-coat) and combined with an iron coagulation.

Drinkwaterbehandeling bestaat uit verschillende stappen, afhankelijk van de kwaliteit van het ruw water. De aanwezigheid van natuurlijk organisch materiaal (NOM) kan problemen veroorzaken in de behandeling en in de distributie van drinkwater. NOM veroorzaakt een hoge coagulantdosering, hoge ozondosering en korte looptijden van actieve kool (GAC) filters. NOM kan een bron zijn voor nagroei in het distributiesysteem en kan de biologische stabiliteit van het drinkwater verminderen. Wanneer het ruw water hoge NOM concentraties bevat, dan moet dit in de drinkwaterzuivering worden verwijderd.

Het drinkwater wordt vanaf de waterzuiveringen naar de onze huizen en bedrijven verpompt via de distributie netwerken. Deze netwerken zijn zeer uitgebreide systemen: naast elke straat en naast veel wegen en door veel weilanden liggen leidingen waardoor het water stroomt. De leeftijd van deze leidingen is divers: in jonge steden of in nieuwe woonwijken zijn de leidingen nog vrij nieuw, maar in de oude stadcentra zijn de leidingen veel ouder, tot soms wel meer dan 100 jaar oud. Het (hoofd) leidingnetwerk in Nederland heeft een totale lengte van circa 120.000 km, ofwel 3 rondjes om de aarde.

Conventional anaerobic digestion is a commonly used technology worldwide and external biogas upgrading is well documented (Wellinger and Lindberg, 2001). Biogas generated in waste (water) treatment facilities is increasingly regarded as an important source of renewable energy. However, generally, the CH4 content in biogas ranges between 55-70%, depending waste(water) composition, and cannot be applied directly for high grade applications such as gas grid injection or vehicle fuel. Conventional biogas upgrading technologies are only cost-efficient when treating biogas flows exceeding 100 Nm3/h. Therefore, cost-effective external biogas upgrading, to remove H2O, CO2, H2S and other trace impurities, was assumed to pose a major challenge for the further dissemination of small-scale decentralized anaerobic digestion technology.

Let’s start with the United Nations Millennium Development Goals Report 2012. Remember the target? Halve, by 2015, the proportion of the population without sustainable access to safe drinking water and basic sanitation. Thanks to China and India the world has met the drinking water target in 2010, but the work is not done yet. The poorest lag behind, especially in Sub-Saharan Africa (Figure 1). Over 40 per cent of all people without improved drinking water live in sub-Saharan Africa. The gap between urban and rural areas still remains wide, with the number of people in rural areas without an improved water source five times greater than in urban areas. Ruralurban disparities in access to sanitation are even more pronounced than for access to drinking water. The number of people forced to resort to open defecation remains a widespread health hazard and a global scandal. Nearly 60 per cent of those practicing open defecation live in India. In sub-Saharan Africa, 75 per cent of the households have to collect water from some distance. The time and energy devoted to this manner of water collection is considerable. For 25 sub-Saharan countries combined, it is estimated that 26 million hours are spend per day, which equals the working hours of the lifetimes of 300 people. An important note: water quality is not accounted for in United Nations report – so results may well be overestimated. But isn’t that what it’s all about? Providing improved water sources, not just any source.

Reclamation and reuse of wastewater for various purposes such as landscape and agricultural irrigation are increasingly recognized as essential strategies in the world, especially for the areas suffering from water scarcity. Wastewater treatment and reuse have two major advantages including the reduction of the environment contamination and hence the health risks and saving of the huge freshwater amounts.

The activated sludge process is the most used process to remove organic carbon, nutrients and other pollutants from sewage and also from many industrial waste waters. The organic fraction of waste water is aerobically respired and partly converted into biomass. The surplus biomass is a by-product of this process and is called excess activated sludge. The main constituents of activated sludge are biomass, organic matter and water. In general, this sludge stream is partly converted in biogas upon anaerobic digestion and partly processed e.g. dewatered and incinerated. One of the drawbacks of the activated sludge technology, is the cost for processing and disposal of the large amounts of excess sludge.

Sewerage and urban drainage systems are capital intensive infrastructures characterised by process and structure complexity. For instance, in the Netherlands (2009), the municipalities spent around €1,2 billion on sewerage (or €151/per household/annum) (Walder, 2011). Proper operation and maintenance of such systems together with rehabilitation will ensure long life of the infrastructures while meeting serviceability requirements. Therefore, insight in the actual status of the assets is a prerequisite for adequate sewer asset management.