Protozoan Mimics

Of the worlds liquid freshwater resources, 97% is stored as groundwater. For millennia, humans have used this resource to provide water for domestic use, agriculture and industry. The water quality of groundwater for drinking water, specifically, is important to human health and therefore the health of society. Access to clean drinking water is a basic human right. The focus of this project is the microbial water quality of groundwater intended for drinking water consumption. Specifically, the microorganism Cryptosporidium parvum is investigated because it occurs in drinking water supplies and is difficult to remove in water treatment plants. C. parvum causes severe gastrointestinal illness and even death in immuno-compromised persons. In order to model the transport of C. parvum in groundwater, a novel surrogate, consisting of glycoprotein- coated microspheres, has been recently developed. A surrogate is needed due to the fact that the real pathogenic microorganism cannot be used in field tests to protect public health, but we need to understand how C. parvum behaves in the natural environment. The proposed project will test the surrogate under various chemical conditions and upscale results from small-scale (30 cm long) and meso-scale (4 m long) column experiments with both C. parvum and the surrogate to the field, where only the surrogates can be tested. The other unique aspect of this project is that the column and field tests will be done in gravel material, for which colloidal transport information is lacking. The general hypotheses of the project are that the glycoprotein-coated microspheres will be the best surrogate for C. parvum, when compared to uncoated microspheres and another potential surrogate which is a non-pathogenic bacterium, B. subtilis, and that it will be possible to upscale the results of the small column tests through the meso-scale to the field scale. This means that parameters calculated from the results of the experiments will have a relationship allowing the assumption that the surrogates can represent the pathogenic microorganism in the field with an adjustment of parameters. The use of protein-coated microspheres will revolutionize the field of water policy and the study of colloidal transport because the method can be extended to model other dangerous microorganisms and will allow more realistic risk assessments for safer drinking water.

Of the world's liquid freshwater resources, 97% is stored as groundwater. For millennia, humans have used this resource to provide water for domestic use, agriculture and industry. The water quality of groundwater for drinking water is important to human health and therefore the health of society. Access to clean drinking water is a basic human right. The focus of this project was the microbial water quality of groundwater intended for drinking water consumption. Specifically, the microorganism Cryptosporidium parvum was investigated, because it occurs in drinking water supplies and is difficult to remove during water treatment. C. parvum causes severe gastrointestinal illness and even death in immuno-compromised persons. In order to model the transport of C. parvum in groundwater, a novel surrogate, consisting of glycoprotein-coated microspheres, has been recently developed. A surrogate is needed, due to the fact that the real pathogenic microorganism cannot be used in field tests for public health reasons. The goal of this project was to validate surrogates alongside C. parvum in small soil columns in the laboratory and to use the surrogates at a field site near Vienna, Austria. In order to do this, an upscaling relationship needed to be established so that the transport of the pathogen in groundwater can be estimated at a larger scale. Therefore, a scaling factor between the surrogate in the laboratory and in the field was found. The same scaling factor can then be theoretically applied to the C. parvum and an estimate of its travel distance in the field can be similarly extrapolated, using a computer model. The experiments in the small columns using surrogates with various values of electrical surface charge showed that the transport is controlled by colloid size and surface charge. However, some of the larger particles did not travel through the heterogeneous material at all. This showed that size, even in coarse gravel, is more important than surface charge. It was found that the most important things to consider when trying to model and predict pathogen transport is the type of aquifer material and the degree of heterogeneity or preferential flow. In this regard, the transport distance, or scale of the protection zone being considered (i.e. 10 m or 1000 m), is key. It was possible to establish an upscaling relationship between the small columns with the real aquifer material and the field by finding a relationship between modelled parameters based on the heterogeneity of the material. The upscaling relationship established may influence policymaking. Additionally, the method for modelling and upscaling colloidal transport in heterogeneous porous material may change how consulting companies in private industry model the setback distance for drinking water protection.