[Reduction of bacteria and viruses in purification plant discharges using microfiltration in a model plant]. / Reduzierung von Bakterien und Viren in Klärwerksabläufen durch Mikrofiltration in einer Modellanlage.

Microfiltration through a membrane matrix of a nominal pore size of 0.2 microns has been applied for advanced treatment of mechanically and biologically treated wastewater. Elimination of bacteria and coliphages as well as the decrease in some chemical constituents were studied at a flow rate of 80 l/h. Microfiltration resulted in a reduction of E. coli, coliform bacteria, fecal streptococci and of coliphages by more than 4 logs in the filtrate. Thus, the quality requirements of EC Directives for bathing water (EC, 76/160) could be maintained. As a result of microfiltration, a 43 +/- 13% removing of the total phosphorous compounds (Pt) in the pre-filtered secondary effluent from 11 +/- 2 mmol/m3 (0.34 +/- 0.06 mg/l) to 6 +/- 2 mmol/m3 (0.19 +/- 0.06 mg/l) was measured. The dosage of FeCl3 (between 30 and 150 mmol/m3) as coagulant before microfiltration improved the reduction of Pt to result in an average value of 75 +/- 16%. After adding FeCl3, orthophosphates (PO4-P) could be efficiently reduced by microfiltration. Thus, PO4-P concentrations in effluent samples were, in most cases, below the detection limit (0.01 mmol/m3).

[Inactivation of bacteria and coliphages in surface water highly polluted by secondary effluent and purified by flocculation and filtration by means of UV irradiation at a pilot plant scale]. / Inaktivierung von Bakterien und Coliphagen in abwasserbelastetem und durch Flockungsfiltration aufbereitetem Oberflächenwasser mittels UV-Bestrahlung in einer halbtechnischen Anlage.

The water of a channel in Berlin which is highly polluted by municipal sewage effluent is treated at the phosphate elimination plant (PEP) Tegel by flocculation and filtration in order to reduce eutrophication in the following Lake Tegel. The elimination of bacteria and coliphages in the effluent of the PEP was investigated in a scale pilot UV irradiation reactor installed at the outlet of the PEP Tegel. The influence of technical parameters such as flow rate and the arrangement of 23 UV lamps in the reactor on the inactivation was tested. The UV irradiation dose was calculated 119 mJ/cm2 and 49 mJ/cm2 at a flow rate of 50 m3/h and 120 m3/h, respectively and for an irradiation zone of 97.5 cm. The colony count of bacteria and concentrations of coliform organisms, E. coli, and feacal streptococci as well as the plaque forming units of coliphages in the influent of the UV reactor were reduced 2-3 lg units by an irradiation dose of 119 mJ/cm2. These elimination was found being only one lg unit at a UV irradiation dose of 49 mJ/cm2. The concentration of E. faecalis and Coliphages f2 seeded into the influent of the UV reactor decreased after UV irradiation by 119 mJ/cm2 by 2-4 lg units and 1-2 power of magnitude, respectively. A UV dose of 49 mJ/cm2 caused only a 90% elimination of E. faecalis and a 75% inactivation of Coliphages f2. Due to heterogenous distribution and the different retention period of the inflowing water in the irradiation zone, the inactivation of E. faecalis and Coliphages f2 was unequal. Both test organisms decreased in the middle of the reactor up to 2 lg units more than at the sides of the reactor. The hygienic-microbiological quality of a secondary effluent from sewage treatment plants can be improved by a combination of flocculation-filtration and UV irradiation due to their additive elimination effect. However, this UV reactor, which was tested under field conditions can only ensure the inactivation of bacteria and coliphages in the pretreated effluent, if more homogenous distribution of the inflowing water can be achieved. Further, the water must be irradiated by a higher UV dose.

[Virus removal from municipal wastewater by biological sewage treatment]. / Virenelimination aus städtischen Abwässern durch biologische Abwasserreinigung.

During a period of ten months, we have determined once a week the amount of viruses in the untreated sewage and in the effluent of two communal sewage treatment plants. Besides, we have compared the virus content of chlorinated and unchlorinated effluent and have determined the amount of viruses in the river in which the effluent is discharged, and in groundwater. In order to concentrate the viruses, the AlCl3-treated samples were filtered through cellulose nitrate filters and the adsorbed viruses eluted with cell culture medium containing 10% fetal calf serum. This medium was used for inoculating cell cultures which were monitored several times weekly for CPE. After the treatment in the plants, the number of viruses was reduced 99.15 and 97.9% respectively. Chlorination of the effluent further reduced the number of viruses by a factor of 5. None of the groundwater samples was viruspositive.