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Berlin Environmental Atlas

02.01 Quality of Surface Waters (Edition 1993)

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Methodology

Environmental Atlas - Methodology

The parameters observed the "Environmental Atlas - Methodology" and are to characterize local and regional surface waters quality. Characterization of waters by the "LAWA Method" (Länderarbeitsgemeinschaft Wasser 1991) proceeds on the basis of a variety of parameters and is summarized for a total evaluation. For this work, however, 5 of the parameters most important for eutrophication of Berlin waters were considered, separately evaluated and presented. They are orthophosphoric-phosphorus, ammonium-nitrogen, the oxygen saturation index, oxygen minimum, and Titer for Escherichia coli. A clear and differentiated presentation of the relatively small investigation area of Berlin can thus be made.

Following the example of water quality maps of the Federal Republic of Germany, classifications were made into 4 quality classes with 3 intermediary levels. Class limits for the 2 oxygen parameters followed water quality mapping classes chosen for use by the LAWA. Concentrations of orthophosphoric-phosphorus and ammonium-nitrogen nutrients are categorized into quality classes so that load levels of the various parameters can be compared. Phosphorus amounts are the limiting factor for algae growth. The eutrophication threshold for dumping up running waters is generally given as 0.01 - 0.03 mg/l. The value 0.01 mg/l is thus the upper limit of quality class 2, "moderately polluted". The classification for ammonium-nitrogen was taken from the Rhine River report of 1978, in which ammonium-nitrogen was classified into 7 categories (IWAR 1978).

Bacteriological parameters of Escherichi coli (E. coli) are observed here in the presentation of water quality for many waters in Berlin used for swimming and water recreation.

Only the most important running waters in Berlin and some running water sections in the state of Brandenburg directly bordering Berlin are included in the appended map. Waters were divided into 99 sections, each usually with a measuring point in the middle of the section. The study results of these measuring sites are considered representative for the entire section.

Values appearing in the summer half-year (1 May to 31 October) were used in order to measure the time-span of biological activity particularly critical for polluted waters. Parameters observed for orthophosphoric-phosphorus, ammonium-nitrogen, and the oxygen-saturation index were mean values of the summer half-year. The most unfavorable single value in this time span is given for oxygen levels and E. coli Titer.

Measuring results are evaluated and depicted in differentiated colors, according to a 7-step scale from "practically unpolluted" to "extremely polluted", similar to earlier presentations of other outflow years in the Environmental Atlas.

Orthophosphate-Phosphorus (PO4-P)

Phosphates exist in water in various forms, but phosphates can only be taken up and used by plants to build up their own physical biomass in the form of dissolved orthophosphoric ions.

The majority of phosphates in Berlin waters come from domestic effluents, particularly from feces. The use of cleaning agents containing phosphates also contributes to phosphate loads.

A large portion of Berlin sewage waters is dephosphorized in sewage treatment plants today by biological phosphate elimination or by chemical phosphate removers.

Figure1
Fig. 1: Concentration of Ammonium-Nitrogen, Nitrate-Nitrogen and Nitrite-Nitrogen in the Teltow Canal for the Outflow Year 1991 (floating medien over 20 days)

Ammonium-Nitrogen (NH4-N)

Nitrogen compounds also highly influence nutrient amounts in water. Nitrogen is present in water in elementary form as well as inorganic and organic compounds.

Organically-bound nitrogen is present in waters as proteins originating from dead organisms. Plants can use the nitrogen needed to build up their own proteins usually only in the form of nitrates and ammonium ions. Nitrogen compounds in water must first be transformed. This is done by micro-organisms that decompose protein substances in water. Other micro-organisms transform the resulting ammonium under aerobic conditions (in the presence of oxygen) first to nitrites and then to nitrates.

During the spring to autumn period of high biogenic activity, the substance transformation process proceeds faster, so that parallel to low ammonium amounts, higher nitrate amounts exist in the waters. Nitrite is only a transitional product in this transformation, so nitrite amounts in waters usually remain low. Figure 1 shows amounts of ammonium, nitrites and nitrates at the Teltow shipyard Schönow measuring station. The depicted substance transformation process in waters at this measuring station were substantially influenced by the discharge pipelines of the sewage treatment plant. Low ammonium loads in summer at this sampling station, behind the Ruhleben sewage treatment plant, are mainly due to the better clarification performance of this treatment plant in summer. The fact that ammonium levels in summer drop more strongly than nitrate levels rise is explainable by the binding conversion (fixing) of nitrates by algae.

The greatest portion of nitrogen compounds in Berlin waters originate from domestic effluents. Sewage treatment plants have particularly negative effects on the oxygen economy of water. They discharge a high proportion of ammonium-nitrogen and the decomposition process to nitrate takes place in the waters themselves. The transformation of 1 mg/l of ammonium-nitrogen to nitrate-nitrogen requires about 4.4 mg/l oxygen.

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