Kontamination mit coliformen Keimen durch Insektenlarven bei der Aufbereitung von Trinkwasser

Contamination of Drinking Water with Coliform Organisms by the Larves of Gnats in the Water Treatment Plant E. coli and coliform organisms are used to judge the microbial quality of drinking water. The presence of these organisms in water indicates that there is a risk for faecal oral transmitted pathogen organisms. E. coli shows the faecal contamination of men and warm blooded animals (mammalian and birds), coliform organisms may be excreted as well from cold blooded animals. The cold blooded animals normally don’t excrete pathogen organisms relevant for human beings. So coliform organisms don’t have such a high relevance for drinking water microbiology. In this paper an incident is presented with a contamination of drinking water with coliform organisms in the treatment plant by the larves of gnats. The larves of the gnats crawl into the treatment chamber via entrance for ventilation. The larves were kept back on the surface of the filters but they contaminated the water with coliform organisms.     

Quantification of Aquatic Nano Particles after Different Steps of Bodensee Water Purification with Laser‐induced Breakdown Detection (LIBD)

The laser‐induced breakdown detection (LIBD) is a very sensitive method for the direct detection of colloids based on the plasma generation on single particles by a focused, pulsed laser beam and the detection of the produced shock wave or plasma light emission. For the determination of colloid sizes the light emission of single plasmas is detected by a microscope CCD‐camera system. With known mean particle diameter and breakdown probability the particle concentration can be calculated. The application of the LIBD to monitor the change of colloid concentration and size during the purification steps of drinking water at the Bodensee (Lake Constance, Germany) water purification plant is shown. The breakdown probability, correlating to colloid number density, decreases with every purification step. By addition of FeCl₃ as a precipitating agent and with an additional filtration step, not only suspended matter, but also colloids are effectively removed. After this process a remaining particle concentration of 50 ng/L and a mean particle diameter of 27 nm are found.     

The Effects of Nutrients on Natural Organic Matter (NOM) Removal in Biological Activated Carbon (BAC) Filtration

Effective biodegradation of organic compounds is one of the major objectives while optimizing biological drinking water treatment processes. Enhancing the biological activated carbon (BAC) filter performance with nutrient addition was studied using chemically pre-treated and ozonated lake water. Three parallel pilot-scale biofilters were operated: one with phosphorus addition, one with a mixture of inorganic nutrients addition, and one as a reference. The addition of nutrients had no statistically significant influence on the natural organic matter (NOM) removal when monitored by total organic carbon (TOC), UV absorbance, and assimilable organic carbon (AOC). However, the addition of nutrients significantly increased the heterotrophic plate count (HPC) bacteria of the filter effluent, while the adenosine triphosphate (ATP) analysis of the attached bacteria did not show any increase in BAC filters. It seemed that in BAC filters the bacterial growth was limited by phosphorus, but the increased bacteria could not attach themselves during the relatively short acclimatization period.     

Production of Drinking Water from Highly Contaminated Surface Waters: Removal of Organic,Inorganic, and Microbial Contaminants Applying Mobile Membrane Filtration Units

In military out of area missions of the Bundeswehr, it can be necessary to produce drinking water even from highly polluted surface waters containing a variety of organic, inorganic, and microbiological contaminants. Thus, mobile drinking water purification systems must be able to remove such contaminants as far as possible to meet the requirements of the German and European drinking water regulation/directive. Presently, two novel drinking water purification units applying membrane filtration undergo intensive long‐term trials carried out by the Bundeswehr. If these trials positively proof the functionality of these units and their ability to remove all possible contaminants they shall substitute so far available devices which use large amounts of chemicals and charcoal filtration for water purification.In the course of a research project, the functionality of the new devices and their efficacy to remove high amounts of algae, microbes, and organic and inorganic pollutants are additionally tested in “worst‐case” field studies. In September 2000, the first mobile drinking water purification unit was tested at the Teltowkanal in Berlin, Germany.This canal was chosen because it carries high burdens of municipal sewage effluents. The results from the fatigue test confirmed the ability of the water purification unit to reduce the concentrations of all contaminants meeting the maximum tolerance levels set by the German/European drinking water regulation.The pre‐filtration device was very effective in removing algae and solid particles to protect the membranes from clogging and to enable an almost maintenance‐free operation. Residues of pharmaceuticals and some other organic contaminants have almost totally been removed from the surface water where they were detected at individual concentrations up to the μg/L‐level.     

Denitrification and Pesticide Elimination in Drinking Water Treatment with the Biodegradable Polymer Poly(ϵ‐caprolactone) (PCL)

A combination of denitrification and pesticide sorption with the biodegradable polymer poly(?‐caprolactone) (PCL) was examined. The function of PCL is to act as carbon source and carrier for the bacteria and simultaneously as sorbent for the pesticide endosulfan. In a short‐term examination (1 month) the addition of the pesticide endosulfan to a continuous‐flow fixed‐bed reactor resulted in an inhibition of biomass production without reduction of the denitrification performance. However in a long‐term semi‐batch reactor test (6 months) biomass production and partly denitrification rates were affected. No significant differences in microbial composition between the reactors were observed. Regardless of the type of reactor or presence of endosulfan, Acidovorax facilis was the main constituent.     

Zum Einfluß von Sauerstoffkonzentration und pH-Wert bei der heterotrophen Denitrifikation Heterotrophic Denitrification: The Influence of Oxygen and pH Value

A demonstration plant for biological heterotrophic water treatment of nitrate polluted groundwater has been operated in Coswig near Dresden since 1989. In this NEBIO tube reactor process the denitrification is achieved in a downstream fluidized bed with continuous regeneration of sintered polystyrene particles as inert carrier material. A nutrient consisting of ethanol and phosphate is dosed in the reactor influent. In the subsequent treatment stages the denitrified water is aerated, filtered through a multilayer and GAC filter, and is finally disinfected with chlorine gas. The influence of changing raw water quality (oxygen content, pH value) on the process performance was examined. Increasing oxygen concentration lowers the nitrate reduction potential and rises the consumptive ratio ΔC/ΔNO₃. The technology shows a high removal performance of 270 g NO₃ m^?3 h^?1 in the range of pH 6.2 to pH 7.3 which is typical for natural groundwaters. The degradation of nitrate is increasingly inhibited for pH values beyond 7.6. Nitrite production occurs significantly in high pH ranges. The results lead to further insight in the stoichiometry of heterotrophic denitrification. By expressing the stoichiometric equations for nitrate and oxygen respiration as functions of oxygen and pH value it could be shown that the influent water quality has strong effects on the consumption of ethanol. A kinetic model was developed to predict the reactor performance under changing raw water conditions. A two stage kinetic model was designed, regarding two main effects: biochemical degradation of oxygen, nitrate and ethanol and distribution of active biomass due to hydraulic properties of the tube reactor. This model may be helpful for reactor design for sites of various ground water qualities.