Onno Kramer

Waternet · Production

Since the 1980’s in the Netherlands, drinking water softening has focused on robustness. However, in more recent years, significant changes were made in the water softening treatment process. These changes include the type of pellet material, NaOH application, targeted total hardness and the acid addition. Yet, these changes have not led to the des...

Since the 1980’s in the Netherlands, drinking water softening is applied on the basis of robustness. However, in more recent years, significant changes have been made at the drinking water softening location of Weesperkarspel, which is responsible for providing drinking water to Schiphol and Amsterdam. A few of those examples are the exchange of pe...

In drinking water treatment plants, multiphase flows are a frequent phenomenon. Examples of such flows are pellet-softening and filter backwashing where liquid-solid fluidisation is applied. A better grasp of these fluidisation processes is needed to be able to determine optimal hydraulic states. In this research, models were developed, and experim...

Granular activated carbon (GAC) filtration is an important unit operation in drinking water treatment. GAC filtration is widely used for its filtration and adsorption capabilities as a barrier for undesired organic macro- and micro-pollutants. GAC filtration consists of two successive phases: adsorption and filtration, capturing the impurities from...

Liquid-solid fluidisation is frequently encountered in drinking water treatment processes, often to obtain a large liquid-solid interfacial surface area. A large surface area is crucial for optimal seeded crystallisation in full-scale softening reactors. Due to crystallisation, particles grow and migrate to a lower zone in the reactor which leads t...

Liquid-solid fluidisation is frequently encountered in drinking water treatment processes, for instance in seeded crystallisation softening processes. For modest superficial fluid velocities, liquid-solid fluidisation systems are generally considered to be homogeneous, as reported in literature. However, during fluidisation experiments with calcite...

Fluid flow through a bed of solid particles is an important process that occurs in full-scale water treatment operations. The Carman–Kozeny model remains highly popular for estimating the resistance across the bed. It is common practice to use particle shape factors in fixed bed state to match the predicted drag coefficient with experimentally obta...

Natural particles are frequently applied in drinking water treatment processes in fixed bed reactors, fluidised bed reactors, and sedimentation processes to clarify water and to concentrate solids. When particles settle, it has been found that, in terms of hydraulics, natural particles behave differently when compared to perfectly round spheres. To...

Natural particles are frequently applied in drinking water treatment processes in fixed bed reactors, in fluidised bed reactors, and in sedimentation processes to clarify water and to concentrate solids. When particles settle, it has been found that in terms of hydraulics, natural particles behave differently when compared to perfectly round sphere...

In the Netherlands, central softening of drinking water is widely applied for reasons of public health, client comfort, economic and environmental benefits. Currently, the detrimental contributions of softening, in particular the use of chemicals and energy, are taken into account in the carbon footprint of the Dutch drinking water companies. The b...

In full-scale drinking water production plants in the Netherlands, central softening is widely used for reasons related to public health, client comfort, and economic and environmental benefits. Almost 500 million cubic meters of water is softened annually through seeded crystallisation in fluidised bed reactors. The societal call for a circular ec...

A novel effective drag relation for liquid-solid fluidisation is proposed, suitable for application in full-scale installations. This is achieved by presenting new insights related to the influence of the temporal-spatial heterogeneity on the effective hydrodynamic drag for large fluidised systems. While heterogeneous flow behaviour can be predicte...

One of the most popular and frequently used models for describing homogeneous liquid-solid fluidised suspensions is the model developed by Richardson & Zaki in 1954. The superficial fluid velocity and terminal settling velocity together with an index makes it possible to determine the fluid porosity in a straightforward way. The reference point for...

About 50% of the drinking water in the Netherlands is centrally softened by the drinking water companies in a process known as pellet softening. In this process a base and seeding material are mixed in an upflow reactor, where subsequently CaCO3 precipitates on a seed core as pellets. The seeding material is usually sand, but recently CaCO3 was int...

Calcium carbonate pellets are produced as a by-product in the pellet softening process. In the Netherlands, these pellets are applied as a raw material in several industrial and agricultural processes. The sand grain inside the pellet hinders the application in some high-potential market segments such as paper and glass. Substitution of the sand gr...

Softening at drinking water treatment plants is often realised by fluidised bed pellet reactors. Generally, sand is used as seeding material and pellets are produced as a by-product. To improve to sustainability, research has been carried out to replace the seeding material by re-using grained and sieved calcite pellets as seeding material. An expl...

In practice, drinking water technologists use simplified calculation methods for aquatic chemistry calculations. Recently, the database stimela.dat is developed especially for aquatic chemistry for drinking water treatment processes. The database is used in PHREEQC, the standard in geohydrology for calculating chemical equilibria in groundwater. Th...

Poster presentation at the IWA World Water Congress and Exhibition, Lisbon In The Netherlands, 50% of the drinking water is treated with pellet softening for various reasons: i) public health (heavy metal solubility), ii) costs (warm water device maintenance, energy and soap requirement), iii) environmental benefits (energy and soap requirement) an...

Fluidised bed reactors are used for water softening in water treatment plants. Recent research shows that under current operation of reactors the crystallisation of calcium carbonate can be hampered. Until now the operational constraints on the fluidised bed have not been exactly known. Experiments were carried out to investigate the fluidisation b...

Central softening has been utilized by the Dutch water utilities since the late 1970s. It was introduced in the water treatment process as a method to supply water with an optimum water composition to prevent lead and copper release and to prevent excessive scaling. Twenty years of experience show that central softening is beneficial for public hea...

In the Netherlands central softening of drinking water is mainly carried out with pellet reactors. The process is efficient and functions satisfactorily. However, actual operational conditions can be improved and corrective maintenance can be diminished. In the present paper an overview of troubles is given and the approach to tackle them is descri...

Ontharding is een dynamisch proces dat door variaties van debiet en kwaliteit continu bijgeregeld moet worden. Daarom is een model ontwikkeld dat verschillende stuurscenario's kan doorrekenen, waarmee het optimale scenario geselecteerd kan worden. Hierbij spelen de deelstroomverhouding, het aantal reductoren in bedrijf en de bedhoogte een belangrij...

Waterleidingbedrijf Amsterdam wil in de toekomst een verdere verbetering van haar waterkwaliteit realiseren. Daarvoor zal een integrale benadering van het zuiveringsproces noodzakelijk zijn. Processturing zal daarbij plaatsvinden op basis van een integraal sturingsmodel van de zuivering. In het kader van Promocit (PROces Modelling and Intelligent C...