The Fairfax County Water Authority applies copper sulfate as an algaecide in the Occoquan Reservoir to control the growth of taste and odor causing algae. The Occoquan Water Treatment Plant removes water from the reservoir for distribution to portions of Fairfax County. Approximately once a day, the treatment plant backwashes one of its five clarifier/filters and discharges this backwash water directly into the Occoquan River. Concern has risen that the plant may be concentrating this copper during treatment, and therefore may be responsible for violations in the toxicity standards for copper in the Occoquan River below the outfall. This investigation has attempted to define the extent of the mixing zone around the Occoquan Water Treatment Plant. A dynamic computer model has been developed based upon the 1988 version of the Tidal Prism Model. Simulations were run on the "worst case scenarios" in the Occoquan River as an attempt to define the mixing zone. It is our initial conclusion that the treatment plant discharge has a negligible effect upon the concentrations of dissolved copper that may exist in the Occoquan River. The treatment plant appears to be removing copper from the raw water rather than concentrating it as initially assumed. Because both the flow and the background dissolved copper in the Occoquan River seem to be controlled by the Occoquan Reservoir, the definition of a static mixing zone boundary is not practical. A dynamic boundary was proposed as an alternative which incorporates the many variables in this system. / Master of Science

Resumé This diplom work is devoted to the ritual purification of the Hebrew in mikva. Mikva is a Hebrew ritual bath which must fulfull certain religious regulations to be understood as properly religious. All the regulations and order regarding the functioning, construction and water, which is allowed to be used, are stated in Misna in the tractate Mikwa'ot. The basis for the ritual adequacy of mikva is water which should have inflow and outflow. Mikva serves to renew ritual cleanliness of a person who became ritually unclean. This ritual dates back to the times when Desater made a commandment to Sinaji. The first people who practiced the ritual were supposedly priests. Those were impurified after the contact with a dead body, carrion of an animal or a snake; after emission of semen or spermatorrhoea. During the times of the first Church the whole population including children cleaned themselves from different impurities. After the deconstruction of the Church the law regualting cleanliness and impurities changed. Today mikva is visited by women firstly before wedding, then after each menstruation period and after giving birth. Men are no longer obliged to practise the ritual after the deconstruction of the Church however even today orhodox Hebrew and chasids clean themselves before important Hebrew...