I. Einleitung : Prof. Dr. R. Braun<br/> II. Die Anlagen für die Auslaugungsversuche : Dipl. Ing. B.M. Novak<br/> III. Die Auswertung der chemischen Untersuchungen : Dr. H. R. Hegi

In the course of the colonization of a seminatural running water biotope by microphytic benthos distinct successioual stages are observed which are characterized by sociological composition and rates of biomass formation. The ratio between photosynthetic activity and accumulation of organic matter vary to a large extent. A high photosynthetic activity is maintained during the phase of vegetational breakdown which is a characteristic phenomenon during the colonization by microphytic benthos. This is of considerable interest in the selection of methods to determine productivity in running water biotopes. Although in macrophytic stands the interpretation of oxygen data with respect to gains in standing crops may be relatively straightforward, great caution is indicated for microphytic communities.

The EAWAG's 'Rheodrom' is a multi-purpose installation, built for hydraulic and ecological experiments, in particular tests with invertebrates in running waters. It is a cyclical system. Approximately 9 m³ water are recirculated through rectangular plexiglass troughs, 6 m in length, 30 cm deep and 15 cm wide. Slope, temperature (4-28 °C) and ground substrate are variable. Light-dark alternations can be produced externally. There is an oxygen saturation of the water at all the time. An increase in heavy metals owing to mechanical attrition cannot be proven.

A new sampling device for the extraction of completely undisturbed samples from lake sediments is described. The core has a diameter of 110 mm and a length of 60 cm or more. Technical prerequisites: sampling tube without interfering structure and with a very sharp end. The valve (to retain the sample) is designed so that water can flow out of the tube when the device is thrust into the sediment but is absolutely tight after sampling. If the sediments is compact (clay-like) sampling can be carried out without closing the tube at the base. There is an automatic closing mechanism for material with a high water content as well as an apparatus for subsequent preparation of the sample.

The application of both a simple rate equation and a novel cross-correlation computational technique to dissolved oxygen records has enabled a determination of the oxygen exchange constant, photosynthesis rate, and rate of respiration for several Swiss rivers. An extension of this method to determine total carbonate dynamics from continuous pH records is also described.<br /> Results for the Aare at Bern (March, 1974) are: 0.38 h^-1 for oxygen exchange constant, 0.6-0.8 mg/(1 h) for respiration rate, and 0.28 mg/(1 h) for mean photosynthesis rate. Moreover the exchange rate for dissolved (but not hydrated or ionized) CO₂ was 0.91 times that for oxygen, and the ratio of O₂ molecules released to CO₂ molecules consumed during photosynthesis was 1.2.

A simplified but realistic model of particulate collection and head-loss buildup in granular media filtration is proposed. In conjunction with a limited number of pilot plant scale experiments, the model should permit estimation of the optimum process conditions for a given filtration problem.<br/> Filtration experiments conducted in small laboratory columns (ID = 10 cm) using glass beads as medium and latex microspheres as model colloids substantiated the assumptions required for model development. Application of the model is illustrated by a hypothetical design problem for a contact filter treating a clay suspension destabilized with a cationic polyelectrolyte.

It was established, on the basis of experiments carried out with pure substances (NaCl, KCl), that the alkali metals Na and K are volatilized in amounts up to 10 mg when subjected to a dry opening-up procedure (ignition at 600° C/3 hours). A decomposition method with nitric acid-perchloric acid is proposed.

Bis vor kurzem war der Vierwaldstättersee mangelhaft erforscht. Genauere Kenntnisse existieren erst seit 1961. Infolge seiner Gliederung in ein System von einzelnen Becken ist der See in verschiedener Hinsicht inhomogen. Die Becken weisen ein unterschiedliches Mischungsverhalten auf (Urnersee mischt alljährlich vollständig durch, Gersauersee und Kreuztrichterbecken mischen unvollständig und von Jahr zu Jahr verschieden tief, das Weggis-Vitznauer-Becken mischt überhaupt nie vollständig). Die Mischungsphase (Zirkulation) ist für jeden See die einzige Möglichkeit der Regeneration (Aufnahme von Sauerstoff, Abgabe gasförmiger Fremdstoffe wie CO₂). Aus diesem Grunde sind tiefe oder windarme Seen mit unvollständiger Mischung auf Verunreinigung bzw. Düngung besonders empfindlich, indem sich hier deren Effekte über Jahre hinweg aufsummieren. Ein typisches Beispiel dafür ist das Becken von Weggis-Vitznau, aber auch der Bodensee. Eine derartige naturgegebene Sensitivität eines Sees erfordert eine besonders sorgfältige Durchführung des Gewässerschutzes.<br/> In einer Reihe von Forschungsarbeiten am Vierwaldstättersee wurden durch die EAWAG grundsätzliche Fragen über Phosphor- und Stickstoffdüngung, über Abbau organischer Stoffe, über Sedimentation und internen Phosphorhaushalt und über die Wirkung des als Phosphatersatzes in Waschmitteln denkbaren NTA bearbeitet. Daneben werden die übrigen Seen der Zentralschweiz im Sinne einer Bestandesaufnahme untersucht.<br/> Der Vierwaldstättersee ist heute schwach gedüngt; sein Phosphatgehalt nimmt jedoch gemäss einer 12jährigen Beobachtungsperiode um rund 7%/Jahr zu. Ein Vergleich mit anderen Seen (Bodensee, Sempachersee, Walensee, Zürichsee, Untersee, Baldeggersee, Hallwilersee, Greifensee) zeigt, dass ein ähnlicher Phosphatanstieg überall vorliegt, mit Zuwachsraten bis zu 20%/Jahr. Bei einzelnen Seen wird der Phosphor-Haushalt zu einem grossen Teil durch periodische Rücklösung aus dem Sediment und Wiedereinbau unterhalten. Die konventionellen Gewässerschutzmassnahmen reichen in solchen Fällen nicht mehr aus; hier muss der zu intensive See-interne Phosphor-Kreislauf durch geeignete Massnahmen direkt unterbrochen werden.

Polycyclic aromatic hydrocarbons from many sources accumulate in soils, recent and ancient sediments, and in many other environmental samples. They occur at low concentrations and in the presence of other extractable materials. We describe an isolation technique utilizing a sequence of gel filtration, adsorption chromatography, and charge transfer complexation. It leads rapidly to aromatic ring-type concentrates that are sufficiently pure for UV, visible, and mass spectrometry. In combination, these techniques resolve adequately very complex mixtures of aromatic hydrocarbons, for instance from fossil fuels, and provide a detailed insight into the hydrocarbon composition, on a milligram to microgram scale. Analyses of some recent near-shore marine sediments demonstrate an unanticipated complexity of the polycyclic aromatic hydrocarbon fraction. The principal hydrocarbon series extends over a wide molecular weight range; minor series are the naphthenologs and thienologs of the major series. The analytical and biochemical implications are discussed.

Aromatic hydrocarbons have long been recognized as ubiquitous pollutants in our environment. It is in general very difficult or even impossible to establish the origin of these compounds. On the one hand their source may be spills of fossil fuels or fallout of incompletely combusted organic material. On the other hand they are widely used as organic intermediates and solvents in trade and industry.<br/> The analytical methods for this class of compounds are discussed. A method based on a combined system of gas chromatography and mass spectrometry is described in detail. The data handling is performed by an on-line coupled, dedicated computer.<br/> Three examples (domestic sewage, diesel fuel, and oil contaminated recent sediment) show the feasibility of the method. An extensive characterization of the aromatic hydrocarbon mixtures in sewage and sediment samples permits conclusions about their origin.

The physical and chemical data of the Rhine waters were studied through the factor analysis technique, the thermodynamic calculations and the geochemical mass balance calculations. The results show that the chemical composition of the Rhine waters are mainly controlled by the ions inputs from the dissolution of rocksalt, carbonate rocks and anhydrite and by NO₃^-, NH₄⁺ and ΣPO₄^3- from fertilizer and sewage. These are subsequently modified by calcite buffering of [Ca²⁺] and [HCO₃^-], the seasonal biological uptake and release of NO₃^- and SiO₂ as well as the in situ formation of chlorite and hydroxyapatite in the river. The average chemical denudation rate of the Rhine drainage area is about 18 mg/cm²yr. The average mechanical denudation rate of the Rhine drainage area below Lake Constance is about 3.2 mg/cm²yr and above Lake Constance about 115 mg/cm²yr. Most of the detritus materials from the alpine area are deposited in the lake.

The effect of domestic sewage effluents after a) mechanical, b) mechanical-biological and c) mechanical-biological-chemical treatment on algal cultures and on natural lake phytoplankton was studied by means of laboratory assays and in situ experiments. The concentrations of phosphorus and nitrogen are almost exclusively responsible for any algal growth. Other constituents which may be present in sewage effluents (e.g. residual amounts of iron originating from the tertiary treatment) do not stimulate substantially the growth of algae.

Model calculations and polarographic investigations show that lead(II) in natural waters is prevalent mainly in the form of PbCO₃° and Pb(OH)₂° species; copper(II) is present primarily as CuCO₃°. Our natural waters are undersaturated with respect to insoluble lead- and copper-phases. The incorporation of these metals into the sediments results from their adsorption on suspended matter.

In view of the chemical composition of the wastes from dairies and cheese factories a complete biological purification should be easily possible. In many instances operation difficulties with aerobic treatment plants due to dominant growth of filamentous organisms with a respective high sludge index was one of the reasons of the restrictive use of such processes. The main reasons for this aberrant microbial composition of activated sludge in such plants have been discussed in the work of Adamse and others.<br /> The present paper gives further information on essential ecological parameters of <em>Sphaerotilus natans</em>, demonstrating that operation conditions for milk waste treatment plants can be stated where the growth of filamentous organisms is more or less completely suppressed and which are readily obtainable in practise. A single biological treatment plant for a small dairy and cheese factory is described and the results of the waste purification and the various operation conditions are summarized.

In einigen Versuchen konnte der Nachweis erbracht werden, daß die Überführung von flüssiger Gülle in einen streufähigen Dünger mit Hilfe biogener Wasserverdampfung möglich ist.

Cast analyses of sludge-pasteurization have been made in six swiss sewage treatment plants. Available dato indicate that specific cost figures will be between sfr. 3,- and 14,- per cubic metre.

A two-box lake model is presented with the subsystems epilimnion (E) and hypolimnion (H) and phosphorus as the limiting nutrient factor. The mean O₂ consumption in H as a function of P loading is calculated and critical P-loading figures above which the lake turns toward eutrophy are given for varying lake mean depth <em>z</em> and hydraulic loading factor <em>q_s</em>. The results agree with an empirical relation between <em>z</em> and P loading given by Vollenweider. In addition, P retention factors are calculated using the model and compared to measured values.

The toxic effect of copper on phytoplankton production is investigated in waters having different complexing capacities. It is demonstrated that a water's complexing capacity does not guarantee that an equivalent amount of copper could be tolerated without adversely affecting algal production. Possible explanations for these findings are offered and discussed.<br /> It is deduced that ionic copper probably is already toxic to planktonic algae at concentrations of about 10^-10 mole/l.

Die Adsorption mittels Aktivkohle ist ein Abwasserreinigungsverfahren, das in den nächsten Jahren sowohl im kommunalen als auch im industriellen Bereich einen wichtigen Platz. erringen wird. Dieses Verfahren eignet sich insbesondere für die Entfernung von gelösten, schlecht abbaubaren organischen Substanzen, die von den herkömmlichen Reinigungsmethoden kaum berührt werden. Die Adsorption ist vor allem dort angebracht, wo das Abwasser hohe Konzentrationen an giftigen oder sonst schlecht abbaubaren Substanzen aufweist, oder wo der Vorfluter im Verhältnis zur Abwasserfracht relativ schwach ist. Diese Bedingungen trifft man an vielen Orten im Schweizer Mittelland an.<br/> Die Adsorption kann als eine Ergänzung der bewährten Reinigungsstufen betrachtet werden. Sie wird sinnvollerweise in Kombinationen eingesetzt, z. B.:<br/> 1. chemische Fällung und Flockung - Elimination von Kolloiden und Ausfüllung von Schwermetallen und Phosphor;<br/> 2. biologische Reinigung - Abbau von gelöstem, organischem Substrat, evtl. auch Elimination von Stickstoff;<br/> 3. Flockungsfiltration - Abscheidung von Restmengen an kolloidaler Substanz;<br/> 4. Adsorption - Entfernung von gelöster, schlecht abbaubarer Substanz.<br/> Auf diese Weise wird kein Reinigungsverfahren überbeansprucht, indem ihm eine Aufgabe gestellt wird, für die es sich nicht eignet. (Beispiele: Abbau von refraktären Substanzen in der biologischen Reinigung; Elimination von ungelöster bzw. gelöster, gut abbaubarer Substanz mittels A-Kohle.)<br/> Bei der Herstellung, Anwendung und Reaktivierung der Aktivkohle stehen bald 50 Jahre Erfahrung in der Industrie zur Verfügung. Die Erfahrung bei der Trinkwasseraufbereitung geht 20 Jahre zurück. Die Erfahrung bei der kommunalen Abwasserreinigung hingegen beschränkt sich auf etwa 10 Jahre in halb-technischen Versuchen und 5 Jahre in technischen Anlagen. Diese Erfahrung ist positiv. Man kann die Adsorption als ein erprobtes Reinigungsverfahren bezeichnen, das nötigenfalls sogar imstande ist, kommunales Abwasser in Trinkwasser umzuwandeln (vgl. Beispiel Windhoek).<br/> Die Adsorption hat sich als ein beständiges Verfahren erwiesen - unempfindlich gegenüber Änderungen in Abwasseranfall, -Zusammensetzung und -Temperatur. Dank dieser Eigenschaften ist sie eine taugliche Ergänzung und gegebenenfalls sogar ein Ersatz für die biologische Reinigung. Im Hinblick auf die Funktionssicherheit lässt sich die Adsorption trotz geringerer Erfahrung sehr wohl mit der biologischen Reinigung vergleichen.<br/> Die Adsorption ist schon heute für den technischen Einsatz bei der kommunalen Reinigung praxisreif. Wir haben zwar keine 50 Jahre Erfahrung, wie das beim Belebtschlammverfahren der Fall ist. Wenn wir aber Jahrzehnte auf ausländische Erfahrung warten sollten, dann bestände die Gefahr, dass viele unserer Gewässer irreversibel veröden würden und nicht mehr für die Trinkwassernutzung verwendet werden könnten.

The drying of sewage sludge, particularly by utilizing energy from solid waste, is examined. In built up areas the odor risk calls for specific measures which often comprise the oxidation of waste gases. It is explained, which additional process cost can be allocated for solutions with odorless flue gases.

The vertical eddy diffusion coefficient in Lake Zürich is a strong function of both depth and season. In the deep lake, the annual oxygen consumptions by the oxidation of organic carbon is balanced out by the equal amount of oxygen supply from above by diffusion.

In den vergangenen Jahren wurden an verschiedenen wissenschaftlichen Instituten Versuche und auf mehreren Kläranlagen Betriebsuntersuchungen zur aeroben Behandlung von Abwasserschlämmen durchgeführt. Die EAWAG unternahm zunächst auf ihrer Versuchsstation Tüffenwies [1] und anschliessend auf der Kläranlage Jona [2] umfangreiche Forschungsarbeiten für die getrennte aerobe Stabilisierung von Kommunalschlämmen. Die Entwicklung dieses Verfahrens bis zur praktischen Einsatzfähigkeit sowie die Abklärung der massgebenden Dimensionierungs- und Betriebsparameter erlaubt nun einen Bezug zum bereits bekannten und bewährten Verfahren der Schlammfaulung, d. h. der anaeroben Stabilisation. Die verfahrenstechnische und kostenmässige Gegenüberstellung dieser beiden Alternativen zur biologischen Schlammbehandlung soll Gegenstand der nachfolgenden Abhandlung sein.

Physical as well as biochemical processes have a significant influence on the material balance of a lake. Mathematical concepts are developed to treat transport phenomena with which a comparison of different lakes under certain systematic aspects becomes possible. A two-box model consisting of the subsystems epilimnion and hypolimnion, for lakes with one specific limiting nutrient factor (e.g., phosphorus) is employed to evaluate eutrophication processes. In particular, a theoretical basis for Vollenweider's [3] empirical relation between specific phosphorus loading and the trophic state is presented. Finally, the inhomogeneous O₂-consumption in the deep part of the lake during summer stagnation is calculated with diffusion theory.

All individuals in the great majority of fish species living in lakes of North and Central Italy, and in Swiss lakes lying north of the Alps, suffer a gill infection caused by a fungus apparently belonging to the genus <I>Branchiomyces</I>. Immunological tests suggest that this organism belongs to the order <I>Saprolegniales</I>.

Presented are hydrocarbon analyses of recent sediments from Lake Zug, Switzerland. The sediments near the densely populated northern shores of the lake contain large amounts of hydrocarbons, predominantly derived from fossil fuels; indigenous hydrocarbons, presumably derived from aquatic organisms, predominate in the middle part of the lake, adjacent to less densely populated areas.

Beim Mischsystem sorgen Entlastungen (Regenüberläufe) dafür, daß die Belastungsspitzen der Kläranlage bei Regen nicht zu stark ansteigen und damit die Wirkung der Anlage unzulässig beeinträchtigen. Seit geraumer Zeit hat man auch eingesehen, daß diese überlaufenden Mischwassermengen dem Vorfluter nicht ohne weiteres zugemutet werden dürfen. Man schreibt deshalb zum Schutz der Vorfluter die Anordnung von Regenbecken vor. Dieser Aufsatz handelt von den möglichen Wegen, die zur Festlegung der Bedingungen führen, die an diese Sonderbauwerke der Kanalisation gestellt werden.

The benthic growth has been investigated during the first 20 days of colonisation in 200 m long river models polluted with 0, 1, 5 and 12% settled domestic sewage. The production of phototrophic and heterotrophic biomass was determined separately at the beginning, the middle and the end of the channels. The distribution of the heterotrophic biomass along the channels may be described by the equation: <em>BZ</em>(<em>w</em>₂) = <em>BZ</em>(<em>w</em>₁) · e^{-<em>k · w</em>} (<em>BZ</em> = heterotrophic biomass production in g · day^-1 · m^-2 surface, <em>w</em> = flow distance in m, <em>k</em> = coefficient for the reduction of heterotrophs along the channels in m^-1). The phototrophs do not significantly contribute to the removal of growth substrates utilized by the heterotrophs. When locations containing identical heterotrophic biomass are compared in two channels treated with different pollution loads, biomass and species composition of phototrophic growth are remarkably different. The concentration change of pollutants in sewage caused by dilution or by biochemical reactions in a selfpurification reach induces clearly different biocenological effects.

The seasonal changes of the biomass production by benthic microphytes have been investigated in outdoor channels (breadth 25 cm, depth 10-20 cm, flow 4 1/sec) for the first 20 days of colonisation. The channels were fed with groundwater to which 0, 1, 5 and 12% settled sewage was added as pollutant. The heterotrophic and the phototrophic portions of the total growth were estimated on the basis of the chlorophyll content of the total biomass. Addition of 12% sewage caused an increase of the heterotrophic biomass at a constant rate during the first 3 to 4 weeks of colonisation. For each season tested the heterotrophic growth is proportional to the sewage concentration within the range from 0 to 12%. At any given sewage concentration the ratio between phototrophic and heterotrophic microphytes undergoes a seasonal variation. Best phototrophic growth occurs in summer in 1 to 5% sewage. Heterotrophic microphytes find better conditions in winter. With an addition of 5% sewage the proportion of phototrophic microphytes in the total biomass is about 10% in winter, and around 70% in summer. At a sewage concentration of 12% the proportion ranges between 2% and 30%. Light incidence represents an important variable for the growth of heterotrophic microphytes.

The daily primary production in lake Lucerne (47° n latitude) was determined at different depths at approximately monthly intervals between 22 July 1969 and 8 May 1970, by summing up series of short term measurements made during each day, using the C₁₄ method. Simultaneously irradiant energy and attenuation of light in the water was measured. It is shown that, considering the photosynthesis-light response the trophogenic layer of the lake can be assumed as homogeneous only from mid October to the end of March. Different known models to estimate daily surface production rates are compared with direct measurements and a new numerical model is described which allows daily production as a function of depth to be calculated. A method is presented which converts the production rate per unit of surface area measured during a standard exposure time to the daily production rate.

Modern technology has introduced a great number of new substances in the natural geochemical cycles and additionally changed the course of existing cycles. The present link between the various systems of the geosphere (land, sea, atmosphere) requires a comprehensive understanding of these interactions. This report attempts to evaluate the natural and material fluxes and the ones introduced by man. The problem concerning in particular the importance of the atmosphere as a medium of transportation and the relationship existing between an atmospheric load by industrial production wastes and the corresponding water contamination is being examined.

Die Ablagerung unbrauchbarer und nicht mehr verarbeitbarer Stoffe ist ein Problem, das weder durch die Intensivierung des Umweltbewusstseins noch durch die Verbesserung der Technologie aus der Welt geschafft wird.

Durch kontinuierliche Waschwasserrückführung in Kieswerken kann eine Abwasserableitung vermieden werden. Wesentlicher Bestandteil dieses Rezirkulationssystems ist das Absetzbecken, das Inhaltsstoffe in dem Maß aus dem Waschwasser entfernt, damit der Waschprozeß nicht beeinträchtigt wird.<br />Bei Betonfabriken und Transportbetonwerken gelingt es, durch die Erstellung und den Betrieb eines Rückhaltebeckens das schädliche und hoch basische Waschwasser, welches bisher Probleme und Kosten zu verursachen pflegte, unschädlich und elegant zu rezirkulieren. Damit lassen sich die erwähnten aufwendigen und schwierigen Ableitungen und Reinigungen umgehen und das Waschwasser wird in den Beton übergeführt, womit eine Beeinträchtigung der Umwelt dahinfällt.<br />Wir bringen es somit fertig, einen kurzen Kreislauf zur sparsamen Betonherstellung uns zunutze zu machen. Damit haben wir einen leider seltenen Fall von Waschwasserverwertung, der gegenüber einer vorschriftsgemäßen Abwasserbehandlung und -ableitung Einsparungen ergibt.

There are several alternative methods for the in situ measurement of light in water. Of the available methods the selenium photo element has been most widely used, largely because of its operational simplicity. The inherent deficiency of this technique, its nonlinear reading, could not be alleviated with the technology available at the time of the method's introduction. It is now possible to achieve perfect linearity with the aid of a modern operation amplifier, owing to the extremely low impedance of the photoelement input. The design of the apparatus is described in detail.