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HANDBOOKBIOLOGY/CHEMISTRY

Chemico-physical testingof water quality

30837.22

Reno Graffitti

HandbookChemico-physical testing of water quality

PHYWE – Series of publications Reno Graffitti

PHYWE-Series of publicationsOrder No.: 30837.22

1st EditionAll rights reserved, including those for translations, reprinting in part andphotomechanical reproductionDesktop-Publishing: Hildegard Richard DTP, D-37115 Duderstadt

© PHYWE SYSTEME GMBH, D-37070 Göttingen

Theoretical section1 Introduction2 Measurement methods and parameters2.1 Colorimetry, photometry, conductometry and

depth of transparency acc. to Secchi2.2 Test parameters2.2.1 Temperature2.2.2 Electrical conductivity2.2.3 Depth of transparency2.2.4 Oxygen2.2.5 The BOD5 value2.2.6 Gross primary production2.2.7 Phosphate value2.2.8 Ammonium value2.2.9 Nitrate value2.2.10 Nitrite value2.2.11 pH2.2.12 Alkalinity value (carbonate hardness)2.3 Disposal of the waste from chemical examina-

tions.3 Description of the quality classes of running

waters4 Description of the trophic levels of running waters

Practical section5 Chemico-physical examinations of water in the

various school classes5.1 Years 7-8 (Sec. 1): Observations and measure-

ments of streams and lakesEVALUATION SHEET 1

5.2 Years 9-10 (Sec. 1): Determine the water qualityby means of chemico-physical parameters: A sim-plified procedure for the characterization ofstreams and shore zones of lakesEVALUATION SHEET 2

5.3 Secondary stage 2 (years 11-13)5.3.1 Examination of running water

Determination of the quality of running water acc.to the BACH systemEVALUATION SHEET 3Characterization of the quality according to char-acteristic quantities selected from the LAWA con-ceptEVALUATION SHEET 4

5.3.2 Examination of lakesExaminations for a body of water characterizationof the open water zone of standing water – sur-face water –EVALUATION SHEET 5Examinations for a body of water characterizationof the open water zone of standing water – deepwater –EVALUATION SHEET 6

6 Equipment supplied with the Ecology case

Phywe series of publications • Handbook • Chemico-physical testing of water quality • PHYWE SYSTEME GMBH • D-37070 Göttingen 3

Contents

4 Phywe series of publications • Handbook • Chemico-physical testing of water quality • PHYWE SYSTEME GMBH • D-37070 Göttingen

Examinations of bodies of water and the determination oftheir quality are carried out using various different meth-ods. These include not only macroscopic biological exam-inations, but also chemico-physical and bacteriologicalmeasurements.The environmental agencies or water authorities who areresponsible for such investigations orient themselves tovery different criteria in the measurement methodologythey apply in their routine investigations. Alongside thequestion of the type of water (running water, standingwater or a mixed form such as running water at a dam) andthe associated different procedures and problems of char-acterization, they must also take into consideration whichthe pollution is to expected or has been previously detect-ed, as well as the form of utilization of the water by man.This includes, for example, not only the continuing and dif-ficult to control loading of large rivers with industrial wasteproducts, such as heavy metals, salts and harmful organ-ic substances, the impairment of the water by waste heatfrom nuclear power stations or the general pollution of thewater by nutrients and faecal matter, but also the aspect ofthe use of polluted water for the drinking water supply or asbathing water.

In order to be able to evaluate different aquatic habitats, afundamental knowledge of the communities in their habi-tats is necessary. This is in fact an indispensible prerequi-site for a useful hydrological study trip and practical exam-inations of bodies of water. It requires an acquantaincewith the conditions of the fresh water habitat (standing andrunning water), with the aspects of typing and biocoeno-logical demarcation, just as much as a characterization ofthe trophy and saproby, of the energy flow and of theturnover in the various habitats as well as their practicalsignificance for the methods for determining water quality.The essence of the recognized methods for determiningwater quality, the new guidelines for evaluating standingwater and also the measurement methods and parametersfor chemico-physical examinations will be described. Thecontents are intended to serve on the one hand as back-ground information for the teacher, and on the other handas a basis of the theory of water examination methodolo-gy. The information on the official methods for the qualitydetermination help towards a realistic view against thebackground of the particular technical demands and in theframework of a critical evaluation of the school possibilitiesfor examinations and the results to be obtained.

5

1Introduction

Phywe series of publications • Handbook • Chemico-physical testing of water quality • PHYWE SYSTEME GMBH • D-37070 Göttingen

6

1 Introduction


2.1. Colorimetry, photometry, conductometry and depth of transparency acc. to Secchi

Colorimetric and photometric methods for measur-ing chemical parametersA whole series of parameters which are examined withinthe context of determining the quality of bodies of water(oxygen content, BOD value, pH and values for nitrate,phosphate and ammonium) are measured in practiceusing colorimetric or photometric procedures. Of these twomethods, photometry has without doubt an advantagewhen it comes to the exactness of the measurement.Because it is more accurate, the use of a photometer is inparticular more appropriate for determinations of the para-meters phosphate (e.g. BACH method; measuring rangeof the (PO4

3-) value for the 0-100 index scale: 0.0-5.0 mg/l)and ammonium (0.0-approx. 13 mg/l). On the other hand,colorimetric measurements are considerably morefavourable in terms of the cost involved. In extensive com-parisons of reagent kits with a photometer and corre-sponding round cuvette tests from approx. 400 individualchemical tests, an astonishing agreement between thevalues determined by the two methods was found. Theseresults lead to the conclusion that one can as rule do with-out the use of the more expensive variant when carryingout comparable tests with groups of students.On the procedure: In both colorimetric and photometricanalyses, there is an absorption of light by colouredmedia. When radiation passes through a medium, or isreflected by it, a part of the radiation is absorbed, wherebythe intensity of the radiation is lessened and the spectrumof the radiation is changed. The amount of absorption isdependent both on the medium and on the wavelengths ofthe irradiating light. In this method, a colouration which ispresent in the medium, or must be brought into it, is mea-sured by means of the resulting spectrum. This providesinformation on the concentration of the substance which isto be detected. If the substance itself does not have acolour appropriate to the determination, a coloured com-pound must be formed by means of reagents.Modern examination technology nowadays makes numer-ous selective and highly sensitive detection reagents avail-able for such analytical procedures.They form the basis ofthe substance or anion detection. The working processesand corresponding chemical reactions necessary for ananalytical principle are not explained in detail, and soremain extensively in the dark for teachers and students(black box procedure). This way of doing things must beaccepted by the user, as a tribute to the commercial inter-ests of the manufacturer.In colorimetry, the examining system works in the visibleregion of the spectrum, i.e. between about 400 and700 nm. The concentration can therefore be determinedwith the naked eye by visually comparing the test samplewith colour standards.

Distinctive features of photometric procedures:The preparatory work for producing a colouration, as is fre-quently necessary for the determination of the concentra-tion, corresponds in principle to that for colorimetry (filterphotometer, order no. 35658.00).The advantages of photometry are the higher accuracyand the elimination of sources of error associated with col-orimetric procedures because of the very subjective visu-al judgement of colour.In photometry, only that part of the light spectrum is usedin which the coloured compound absorbs, i.e. the light pro-duced by a tungsten filament lamp, with a spectrum ofrange approx. 370-770 nm, is bundled by a converginglens and then split up prior to measurement by means ofa special coloured glass filter which is inserted in the pho-tometer. This filter is selected according to the substanceto be measured. The analytical result is particularly exactwhen the spectral range available for the measurement isnarrow, and the measurement can be made in the area ofthe absorption maximum of the substance to be mea-sured. The filtered light beam passes through the analyti-cal sample in the cuvette, and the transmitted light is con-verted by the so-called receiver of the photometer intoelectrical current, whose strength can be read off from thedisplay. The extinction measured is usually taken as thebasis for the calculation of the analyical value (in mg/l).The photometer must be set to 0 with a blank test (a sec-ond cuvette with untreated sample) prior to the measure-ment. This eliminates the influence of any loss of lightintensity caused by the filter, the cuvette or its contents. Itensures that the loss of light intensity subsequently mea-sured for the test sample is only that caused by the reac-tion colour of the substance whose concentration is to bedetermined.As in this examination method only very small quantitiesare often worked with, and the students mostly have littleexperience with titration procedures, we strongly recom-mend that repeat measurements be made, and then aver-age values calculated from them.

Conductometric methods for determining electricalconductivityThe presence of ions in water determine its conductivity.This is a measure of the contamination of a body of water.The electrical resistance can be measured with conductiv-ity measuring instruments with a digital display (conductiv-ity meters). Reference values always relate to 20 °C. Theinstruments are designed with automatic temperaturecompensation, so that measurement results are alwaysadjusted to this temperature.

7

2Measurement methods and parameters


8

2 Measurement methods and parameters


The Secchi method for determining transparencyThe depth to which a body of water is transparent is ameasure of the pollution of that water with various sub-stances. The depth of transparency (turbidity) is measuredwith a Secchi disc (order no. 65568.00). This is a heavy,flat, white disc of 25 cm diameter. It is lowered plumb downinto the water by means of a suspending cord with dis-tance markings. The depth is determined at which the disccan just no longer be seen with the naked eye. The mark-ing on the cord allows a relatively exact depth of trans-parency determination. (see also section 2.2.3).

2.2. Test parametersThe physical and chemical parameters which are usedare: temperature, electrical conductivity, depth of trans-parency, oxygen content/oxygen saturation, biochemicaloxygen demand (BOD5), gross primary production (mea-sured as the oxygen value of photosynthesis), phosphate(PO4

3-) value, ammonium (NH4+) value, nitrate (NO3

-)value, nitrite (NO2

-) value, pH and alkalinity (carbonatehardness) value.When measurements are to be carried out, it is necessaryto exactly follow both the operating instructions for theequipment used and the directions for use of the test kitsfor the colorimetric procedure.The evaluation curves used in the BACH examination sys-tem are very helpful when evaluating the quality of thewater, particularly for the area of running water (see Fig. 1).

2.2.1. TemperatureThe heating effect of the longwave light ("red" and "infra-red" portions) which is absorbed is predominately respon-sible for the warming of the water. The activities of theaquatic organisms are fundamentally temperature depen-dent. This is true for plants and for animals. As an exam-ple, the productivity of the phytoplankton rises withincreasing temperature because of the increase in the rateof metabolism. This can accelerate the eutrophicationprocess in a lake. Intensive irradiation by the sun can, as aresult of the increased warming and the associatedenlargement of the epilimnion, lead to a change in theenergy flow conditions throughout the whole of the body ofwater. The heightened productivity in the surface watercauses an increased lack of oxygen in the deep water inthe vicinity of the sediment because of the increased con-sumption by reducers. Active animal life is tied to a definitetemperature range (between approx. 0°C and max. 50°C).The tolerance ranges of animals to a changing water tem-perature are very different. Particularly stenothermal ani-mals (animals which live only in a narrow temperaturerange) can easily be driven from their ancestral habitat bylarge temperature fluctuations. Waste water dischargescan effect such changes in temperature, for example.

The evaluation guidelines which are necessary in connec-tion with the methods for characterizing waters and for thequality data ascertainment show, for the running waterarea, a spectrum of from < 14 °C (CI value 100 for waterquality class I / oligosaprobic zone) to > 30 °C (CI value 1for water quality class IV / polysaprobic zone).A comparable spectrum is given for the evaluation criteriafor the surface water of a lake, whereby naturally the tem-perature scale in the lower section begins at higher tem-peratures: from < 20 °C (oligotrophic) to > 27 °C (poly-trophic). Because of the special conditions (stratification),the temperature spectrum range given for deep water isfrom < 4-5 °C (oligotrophic) to > 16 °C (polytrophic).The water temperature is also of great significance for theoxygen saturation of the water. The absorbing power ofwater for oxygen is temperature dependent: At 0 °C wateris capable of taking up 14.16 mg of oxygen per litre, at30 °C however only about half of this, i.e. 7.35 mg of oxy-gen. A determination of the oxygen saturation must there-fore always be accompanied by a measurement of tem-perature.Like all animals, fish also have a certain tolerance rangefor water temperature. Whereas the upper limit for carp isapprox. 30 °C, rainbow trout can only briefly tolerate a tem-perature of 27 °C and river trout can no longer exist at tem-peratures above 23 °C. A rise in temperature of 10°Cincreases the basal metabolic rate by a factor of 2-3 times,and as this is accompanied by a doubling of the oxygenconsumption, one can well understand how great the prob-lem of the increasing oxygen requirement with rising tem-perature can be for fish, particularly when one also takesinto consideration, that with increasing temperature theoxygen saturation decreases.

2.2.2. Electrical conductivityThe electrical conductivity of water is determined by theconcentration of ions present in it. The number of thesecharge carriers is, however, extremely small in pure (unpol-luted) water (see 2.2.11 / pH). Further to this, it is temper-ature dependent. Even a small content of acids, bases orsalts (electrolytes), which are almost completely dissociat-ed into their ions in dilute solution, cause a distinctincrease in the electrical conductivity of water.For these reasons, this BACH parameter (see Fig. 1) isone of the components for the characterization of waterquality.Conductivity is measured in siemens per centimetre(S·cm-1). The unit siemens is defined as the reciprocal ofthe ohm (S = 1/Ω).The electrical conductivity of pure wateris approx. 0.04 µS·cm-1, that of rainwater is approx.5-30 µS cm-1, and that of a good quality water is approx.100-300 µS·cm-1.

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Fig. 1: Evaluation curves for the test parameters within the context of the BACH method for evaluating the quality of run-ning water.

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2.2.3. Depth of transparencyThe depth of transparency (turbidity or depth of visibility ofa body of water) depends predominately on the absorptionof the remaining light intensity. Very different types of sub-stance, and also organisms, can participate in the absorp-tion process: Phytoplankton and zooplankton, eluted min-erals and pigments, as well as a wide spectrum of varioussubstances from the so-called "water humus".These makeup the dissolved yellow substances which, in comparisonto the inorganic substances, have an outstanding influenceon the so-called "light climate" of a body of water.Fig. 2 shows how great the influence of humic substanceson the light conditions in a lake is.In polyhumic lakes, measurements at 1/2 m depth haveshown less than 5% of the light intensity there than that atthe water surface. Even in a lake with a comparatively lowcontent of humic substances, only 15% of the irradiatinglight intensity is found at a depth of 2 m.The absorption coefficients for the various wavelengths ofthe light spectrum are different. The green-yellow con-stituent of sunlight penetrates through to deeper depths,whereas the radiation of the UV and violet sector on theone hand, and the long-wave red radiation on the otherhand, are more intensely absorbed in the surface layers.In surface water, therefore, plant life (phytoplankton) is onlypossible down to a depth of from 1 m to maximally 100 m

(further in exceptional cases), in dependence on the inten-sity of the incident light. This region of water is within theso-called compensation depth, which is the zone in whichthe oxygen consumed by respiratory processes is justcompensated for by the amount of oxygen produced byphotosynthesis.Measurements of the depth of transparency detect, amongother things, the dissolved yellow substances which areincreasingly formed with the accumulation of organic sub-stances in the water. Lignin which is produced during thelignification of parts of plants and which only a few organ-isms (some bacteria and predominately higher fungi) candecompose plays a great part in these.The depth of trans-parency is therefore a direct measure of the accumulationof organic substances in a body of water. The determina-tion of this value is, however, not without problems, as thecomparability of the irradiating conditions on different daysof measurement and at different times of measurement(position of the sun) is limited.A sound determination of the depth of transparency in run-ning water is in most cases not possible, as a large part ofthe waterbody is far too shallow. This is one of the reasonswhich supports the use of the BACH parameter within thescope of a chemico-physical examination of water, and sois against the use of the G.R.E.E.N. parameter for this (seep. 34 and 38).

Fig. 2: The absorption of light at various depths of LakeConstance.(The measurements were made at different times andshow which influence the various factors, e.g. phytoplank-ton stand or humic acids, have on the relative brightnessof various layers of water)

Fig. 3: The connection between oxygen content, tempera-ture and water quality class

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2.2.4 OxygenOxygen content and oxygen saturationWhen saturated, water contains only 1/20 to 1/30 of theatmospheric oxygen content.The absorption power for oxygen is temperature depen-dent. The saturation values range, in dependence on thetemperature, from 14.6 mg oxygen/l water at 0°C to6.59 mg/l at 40°C (at an atmospheric pressure of1013 hPa).The oxygen content of a body of water is of immenseimportance in connection with the evaluation of lifeprocesses. The relationship between the oxygen contentand temperature to the quality class determined for a bodyof water is shown in Fig. 3.In the chemical index (CI) acc. to BACH, which is definedby 8 parameters, the oxygen content is taken into consid-eration under oxygen saturation, and also under biochem-ical oxygen demand (BOD value).These two parameters alone are responsible for 40% ofthe weighting.Oxygen is required by almost all organisms in water for therespiratory processes in the cells (exceptions: anaerobesand facultative anaerobes). This is equally true for plants,animals and microorganisms (bacteria, protozoa, fungi).

Fish waters should have an oxygen content of at least5 mg/l, and the critical limit is 3 mg/l. Catfish and carp diewhen the oxygen content is below 1 mg/l, for example.

The oxygen cycleOxygen molecules continually go into solution in waterbecause of the relatively high partial pressure in theatmosphere. The processes of oxygen uptake are not onlytemperature dependent (see above), but are also promot-ed by movements (currents) and the circulation caused inthe water by them. A raging mountain stream thereforetakes up considerably more oxygen from the atmospherethan a slowly running stream in the plain. The oxygen val-ues in the surface water of a lake are distinctly higher onstormy days than on normal days.Alongside the uptake from the atmosphere, biogenicprocesses play a major role in the oxygen cycle. Plantscontinually generate oxygen by photosynthesis, in depen-dence on the conditions with regard to light and carbondioxide, and only consume a small part of this themselves.It is the basis of the respiratory processes of all animal andalmost all microbial life in water.Wherever increased plant growth occurs because ofanthropogenic inputs of nutrients (eutrophication), greatlyincreased oxygen values can result during daytime andunder favourable growth conditions.They can reach ordersof magnitude which are distinctly above 100% oxygen sat-uration.

The influence of oxygen on the self-purifying proces-ses in running watersThe input of atmospheric oxygen into running water isstrongly promoted by the continual movement of the waterand the associated mixing of the water. The oxygen con-tent is as a rule sufficiently high for the respiratory process-es of plants, animals and microorganisms.This can change abruptly and gravely, however, whenthere is a massive input of biologically degradable sub-stances from a discharge of farm effluent or domesticsewage, for example. The change in the habitat conditionsfrom those of the previously "clean" habitat are usually faroutside the limits of tolerance for almost all organisms inthe natural habitat community. They are therefore drivenfrom their habitat, and new forms which are better suited tothese conditions settle this strongly polluted habitat region.These are mostly protozoans, bacteria and fungi.Sphaerotilus natans, the so-called "sewage fungus", is abacterial species which is found in highly polluted water,and which causes a slimy and furry riverside plant cover.This species, which belongs to the chlamidobacteria,forms rod-shaped cells which hold together during the con-tinuing dividing processes, and so form long threads.Sphaerotilus is to be predominately found in water which,after having been highly polluted, contains an increasedamount of amino acids and still sufficient oxygen. Withincreasing consumption of the oxygen by microorganismsduring their degradation processes, the Sphaerotilus plantcover decreases (see Fig. 4).

Fig. 4: The changes in chemical and biological parametersfollowing an inflow of organic wastewater and further alongthe self-purification course of a running water

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In addition to this "sewage fungus" there is a whole seriesof typical organisms which occur in the communities whichcharacterize the waste water zones. These include furtherbacteria (up to 1 million bacterial cells per cm3), amoeba(e.g. limax-amoeba), flagellates, ciliates (includingParamecium putrinum and Vorticella microstoma) andgenuine fungi, such as the genuine sewage fungusLeptommitus lacteus, which Sphaerotilus resembles.Only a few species of macrorganisms which can be rec-ognized well with the naked eye are present in such high-ly polluted water.They are then frequently present in abun-dance, however. Mass propagation of sludge worms(Tubifex), bloodworms (Chironomus), leeches (Hirudinea)or rat-tailed larvae (Eristalis sp.) are then not seldom. Likethe microscopic organisms, they also contribute to a suc-cessive improvement of the water quality by their utilizationof the organic pollutants. The tubifex worms, for example,eat enormous quantities of sediment and "free" it from theorganic nutrients in doing so.As a result of the purifying process carried out by this het-erogeneous group of "refuse collectors", the organic pollu-tion in the afore mentioned water zones gets less and less,the plant nutrients formed (e.g. nitrate) cause an increasedgrowth of algae and, because of the photosynthesis activ-ity of the phytoplankton and the riverside plants, togetherwith the gas exchange processes brought about by themovement of the water, there is an increasing rise in theoxygen content. Such water can regain its original qualitywithin about 6 to 10 hours and after flowing over a distanceof approximately 10 km. In each of the habitat segments ofthis purification stretch, as characterized among otherthings by their oxygen contents, different biocoenoses(biotic communities) are to be found. The changes in theorganisms present in these communities occurs "flowing-ly".The special significance of the so-called BOD value in thecontext of the examination of running water is discussed inparagraph 2.2.5.

The special conditions of a lake*In contrast to running water, there is a typical seasonalstratification in Central European lakes (mostly dimictic, i.e.the water stagnates in summer and in winter).The stagnation phase in summer leads to special condi-tions in the surface water and deep water of a lake.After the turnover of the body of water in Spring, the plantnutrients are relatively evenly distributed in the water.The phytoplankton in the epilimnion therefore has verygood growth conditions in early summer, with more inten-sive exposure to the sun and increasing water tempera-ture. In polluted lakes, the washing in, for example, of largeamounts of nitrate and phosphate causes growth condi-

tions to be even more considerably improved. The highproductivity of the phytoplankton inevitably results in veryhigh oxygen saturation values. In surface water layers, asudden increase in temperature during the day can causethe saturation values to more than double (see Fig. 5). Theoxygen values naturally correlate with the values for assim-ilated carbon (see Fig. 6).Exceptionally high oxygen saturation values are indicatorsof eutrophic lakes. These values are also taken into con-sideration in the saturation curves according to BACH (seeFig. 1). The highest index values are at 100% saturation,above this point the index curve shows a sharp drop to sat-uration values of more than 160%.Under these conditions, the content of dissolved oxygencan be subject to extreme change during the transitionfrom day to night. As a result of the strong phytoplanktondevelopment, there is also strong growth in the subse-quent trophic levels, from zooplankton to fish.

Fig. 5: Temperature and oxygen layers in an oligotrophiclake and in an eutrophic lake at the end of the sommerstagnation(the zigzag curve of the oxygen content can be explained by the relative-ly high concentration of organic decomposition products in the disconti-nuity layer, whose decomposition requires considerable amounts of oxy-gen.)

*A lake is used here exclusively as the most well known example of abody of standing water.

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This brings with it an overall increase in the oxygen con-sumed by the respiratory processes of all the organisms(including the phytoplankton), which can lead to consider-able oxygen deficits at night, which are then more thancompensated for during the day.In a relatively clean lake, the saturation values in deepwater are very low at the end of the summer stagnation.This is quite natural, and can be explained on the onehand by the stratification and the related barrier to beingsupplied with oxygen from the surface water, and on theother hand by the activity of the reducers, predominately inthe deep water near to the sediment. A major part of theoxygen which was brought into the deep water during theSpring overturn has been consumed in the decompositionprocesses carried out on organic material which sunkdown from the upper water layers. This consumption is inthe end primarily dependent on the gross primary produc-tion of phytoplankton in the surface water. Bacteria take aspecial place among the reducers. Bacteria are, whencompared on the basis of unit weight, much more activefrom the physiological point of view than higher organisms.For example, they have a considerably more favourableratio of turnover to biomass than other comparable organ-isms. The experimentally determined oxygen consumptionof Bacterium subtilis is approximately 2980% of its bodyweight per day. In comparison, the measurement of theoxygen consumption of paramecium gives a value of onlyabout 30% of its body weight per day.This result shows how effective bacteria carry out theiractivity of converting organic substances into inorganicsubstances. It also shows, however, how quickly bacteriacan change the oxygen conditions in deep water whengiven sufficient "food" (and additionally in respect of theirhigh rate of propagation).The processes described above usually lead to seriouschanges in the oxygen conditions in deep water. Accordingto the degree to which they occur, considerable oxygendeficits can result very early in the summer stratification.Organic matter can no longer be completely decomposedunder aerobic conditions (with consumption of oxygen).This leads to various developments which dictate the pro-gressive eutrophication of a body of water and start thebiological collapse of a lake. The end of this developmentis the terrestrialization of the body of water.One of the various developments is the formation of hydro-gen sulphide. In the natural cycle of a body of water, organ-ic sulphur compounds are oxidized to sulphate. Oxygen isrequired for this. When oxygen is not available, hydrogensulphide (H2S, desulphurication) is formed. This gas isformed in anaerobic sludge and is not only of problematicnature for the fish population in certain concentrations, butis also very poisonous to plants. In addition, it can rise upinto the surface layers and, after oxidation there, even fur-ther increase the amount of plant nutrients.

Following the Autumn turnover of the body of water, thehydrogen sulphide can cause a lasting disturbance to theepilimnion habitat community because of its toxicity.Oxygen deficits in the deep water in the vicinity of the sed-iment also lead to a disturbance in the phosphorus-iron-cycle.As long as there is sufficient oxygen in the water-sedimentzone, the phosphate ions (PO4

3-) in the water react withiron ions (Fe3+) to form a water insoluble iron-III-phosphatecomplex (FePO4), whereby the minimum factor phosphatewhich is so important for plant growth is removed from thewater (phosphate elimination). This so acts againsteutrophication. When the oxygen in the deeper layers isspent, the complex is split in this reducing environment toiron-III-ions and phosphate ions. A powerful push is givento the plant nutrient phosphate which is so important forthe increase in biomass. The "algal bloom" in the surfacewater is increased at the latest after the next turnover ofthe water.

2.2.5. The BOD5 valueThe biochemical oxygen demand (BOD value) is theamount of oxygen which is required by microorganisms, at20°C, to oxidize the organic substances present in waterwithin the scope of their metabolism. The BOD value isalso called the oxygen consumption. BOD5 means the oxy-gen demand over a period of 5 days. It is measured as fol-lows: A sample bottle containing the water to be tested isclosed free of air bubbles immediately after the oxygencontent has been measured, then wrapped in aluminiumfoil (to prevent photosynthetic activity of the phytoplankton)and left to stand 5 days at room temperature. The oxygencontent is again measured and the difference taken todetermine the BOD5 value. We can derive from the infor-mation given in the previous chapter, that the value mea-sured by this procedure can be directly related to the pol-lution of the body of water with organic substances.Should reasons of organization make it difficult to carry outthe second oxygen measurement after exactly 5 days with-in the scope of school water testing, then other intervalscan be taken and a conversion factor (CF) be used to allowa comparison of the test results:

Test after 2 days: BOD2, CF = 1.85Test after 3 days: BOD3, CF = 1.37Test after 4 days: BOD4, CF = 1.136Test after 7 days: BOD7, CF = 0.855

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We can see from the course of the BOD5 evaluation curve(Fig. 1), that oxygen demands of up to and over 14 mg/l arepossible in highly polluted water.This means that the value determined for the oxygen con-tent in the first measurement can frequently be so low inthe case of critically polluted and highly polluted waters,that the procedure described above must be modified toobtain useful results: The oxygen content of the samplemust be distinctly increased (up to more than 30 mg/l) bypassing pure oxygen through it for several minutes.A long and vigorous shaking of the sample in an open ves-sel can also lead to the wanted increase in the oxygen con-tent. In each case, the oxygen content must be again mea-sured subsequently, to then utilize the proceduredescribed above.Because of their low oxygen demand, bodies of water witha BOD5 value of up to 4 mg/l are for example suitable asfish water, whereas those with a BOD5 value of 4-10 mg/lare only of limited suitability.

2.2.6. Gross primary productionThe significance of phosphorus and nitrogen as limitingfactors for plant growth is described in sections 2.2.7. -2.2.9.The major element contained in organic compounds,and so also for the organic synthesis of plants, is carbon.This carbon is as a rule assimilated as CO2 in the cellularprocesses of photosynthesis, i.e. in a complicated meta-bolic process which takes place under the influence of

energy from sunlight (the reason why CO2-assimilation isa synonym for photosynthesis). In the end, glucose is pro-duced.The phytoplankton in the surface water produces largequantities of glucose on exposure to strong illumination(Fig. 6), whereby this production is dependent on theamount of light radiated in and the nutrients which areavailable.During the course of evolution, submersed plants havedeveloped different mechanisms for taking up the carbonpresent in water. To outline these, we must first discuss, insimplified form, the chemical conditions for the availablilityof the various sources of carbon:Carbon is on the one hand present in water in the form ofphysically dissolved carbon dioxide, whereby relativelylarge amounts of carbon dioxide can be present in water.This "free" CO2 is taken up by all aquatic plants. Somespecies (Fontinalis types: e.g. submersed water moss,Batrachospermum/red algae, Chlorella/green algae) canonly utilize this form of carbon and are therefore suitable asindicators of relatively unpolluted water.Carbon dioxide reacts to a small extent with water to formcarbonic acid:

H2O + CO2 —> H2CO3

When there is a lot of carbon dioxide dissolved in water,the amount of carbonic acid increases, so that the pH ofthe water decreases. In a body of water in which a lot ofcarbon dioxide is liberated during the decomposition oforganic substances (bacteria, fungi), therefore, conditionswill become increasingly acidic.On the other hand, the pH increases as a result of a con-tinual uptake of free carbon dioxide from the water, where-by in hard water pH values of up to 8.5 can be reached.Together with the Ca2+ ions present in water, carbonic acid(H2CO3) forms sparingly soluble calcium carbonate(CaCO3), which reacts with any remaining carbonic acid toform calcium hydrogen carbonate (Ca(HCO3)2).This calcium hydrogen carbonate represents a furthersource of carbon for the plants in water.Its function in connection with the hardness of the waterand the buffering capacity is described in section 2.2.12(alkalinity).When the carbon dioxide dissolved in the water has beenconsumed, various types of plants (Elodea types: Elodeacanadensis / American waterweed, Myrophyllum /Scenedesmus type: green algae of genus Scenedesmus)utilize the carbon dioxide fixed in calcium hydrogen car-bonate: After taking up the calcium hydrogen carbonate inthe leaves, carbon dioxide is "torn" from it and the reactionproduct, calcium hydroxide (Ca(OH)2), is eliminated.Whenit emerges from the upper side of the leaves, the calciumhydroxide reacts with any calcium hydrogen carbonate

Fig. 6. Assimilation of carbon in different depths of a lakewith strong solar radiation

15



remaining in the water to form sparingly soluble calciumcarbonate:

Ca(HCO3)2 + Ca(OH)2 —> 2 CaCO3 + 2 H2O

This sparingly soluble calcium carbonate can then be seenas a white coating of calcium carbonate needles on theleaves of the submerged plants ("biological decalcifica-tion"; see Fig. 7). These processes lead to a decrease inthe carbonate hardness of the water. At very high pH val-ues (pH > 11), carbon is finally only present in water ascarbonate (CO3

2-).After intake of carbon by the plant cell, CO2 fixing occurs,either via the Calvin cycle at the acceptors ribulose-1,5-diphosphate or (with C4 plants) at phosphoenolpyruvate(PEP), which are each starting materials for certain reac-tion cycles, at the end of which starch is produced.When determining the production conditions in the surfacewater of a lake, a measurement of the oxygen content iscarried out alongside the determination of the BOD valueand the oxygen saturation value. This enables quantitativestatements to be made on the production of biomass fromthe measurement of the "waste product" oxygen which isproduced by photosynthesis.The corresponding trophic level can then be found from thevalues determined, using the standardized guidelines intabular form.The oxygen liberated during the formation of biomass isutilized on the one hand for the cell respiratory processesof the plants themselves, and on the other hand for thoseof the consumers of the various trophic levels and thereducers. On considering these complex connections, wecan see that a continuous measurement of the oxygencontent in water is not an adequate method for indirectmeasurement of the gross primary production. For thisreason, the following procedure is chosen: Two samples ofsurface water are taken at the test location from a depth ofapproximately 1-1/2 m, each in a separate narrow-neckedbottle, and the actual oxygen content of each determined.One of the bottles is wrapped in aluminium foil to keep thesample in complete darkness and the other bottle is leftexposed to normal daylight.The temperature of the place where the bottles are keptshould be approximately the same as that in the water atthe test location.*

The two samples are held under these conditions for 24hours, then each is subjected to another measurement ofoxygen content. The expected increase in the oxygen con-tent of the water sample in the bottle which was exposedto light is a measure of the so-called net primary produc-tion. In the case of the darkened bottle, the differencefound is a measure of the total oxygen consumed by therespiratory processes of the organisms. On adding thesetwo values, we have the value for the gross primary pro-duction (Fig. 8).

Fig. 8 Productivity determination by the light-dark bot-tles procedure

Fig. 7 Sources of carbon for aquatic plants

* The departure from the scientific practice for the measurement procedure, i.e.holding the two bottles in the water at the test location at the appropriate depth, ismade because the expenditure for this is too great. The small changes in concen-tration which result from the relatively brief holding time (5 hours) also demand toomuch of a school measurement procedure.

16



2.2.7. Phosphate (PO43-) value

According to a rule first formulated by J. von Liebig, thenutrient which is present in the lowest concentration deter-mines the total dimensions of plant growth. Phosphate isusually a minimum factor for plant growth.The element phosphorus is of importance in the metabo-lism of organisms in diverse respects (e.g. as a componentof nucleic acids and ATP).The phosphate concentration is relatively low in unpollutedground water. The basic loading of waters in Germany isapprox. 2.4 kt/a, which is very low in comparison with theanthropogenic pollution (approx. 55 kt/a). No dissolvedphosphate should be present in an unpolluted lake.Even in polluted waters, the phosphate concentration iscomparatively very low. This is also shown in the BACHevaluation curve (see Fig. 1). The index spans almost90 points in the range from 0 mg/l to 1.2 mg/l. Usefulorthophosphate values can only be determined with a rel-atively sensitive measuring methodology.Up to the beginning of the 1930's no dissolved phosphatecould be detected at any time of year or any position inLake Constance. This means, that the small amounts ofphosphate originating from the geological bedrock circu-lated exclusively and permanently in the nutrient cycle.It was inevitable, however, that the increase in these smallamounts of phosphate due to anthropogenic dischargesresulting from overfertilization of fields and meadowswould cause changes in the plankton development. Withinthe course of 25 years, the orthophosphate values in theupper part of Lake Constance increased from 0 mg/m3 toapprox. 25 mg/m3.The causes of the increased loading of bodies of waterwith phosphorus are the continual input of phosphorus inpredominately undissolved form (e.g. iron phosphate, cal-cium phosphate, biogen bound organic phosphate) fromagriculture by soil erosion and surface rainwash, and asinputs of phosphorus in predominately dissolved form (e.g.orthophosphate, complex phosphates, organic phos-phates) from waste water discharges. Phosphorus pollu-tion is now usually related to total P, as a determination ofthe eutrophication potential of undissolved P compoundsis not easily possible, and, besides this, also depends onthe type of water itself.

The development of P-pollution in surface waters:Even in 1975, alone in the Federal Republic (WestGermany), over 100 kt/a was still brought into surfacewaters. Of this, 80% was from waste water discharges, andover half of this (42%) was due to phosphates from deter-gents. Determinations showed a considerable lessening ofthe pollution, particularly in this area, after the beginning ofthe household use of P-reduced or P-free detergents in the1980's. In addition, waste treatment plants were fitted outwith chemical purification steps with purposeful phospho-rus elimination. Whereas the phosphorus from human fae-ces is mostly present in the form of orthophosphate, the P-input from other sources (detergents, industrial waste dis-

charges, rainwater) is mostly in the form of condensedphosphates, which are however hydolyzed to orthophos-phate in the biological clarification step. It is nowadays pos-sible, and justifiable from the cost point of view, to usechemical precipitation to decrease the phosphate content(calculated as phosphorus) by 90-95% and so reduce it to0.5 mg/l or less.Despite the improvements spoken of above, one stillexpects a total P-inflow of approx. 30 kt/a from thesesources ("point sources").The limiting value set by law for the discharge of clarifiedwaste water into outlet channels is 1.8 mg/l total-P. Thisvalue is in the region of the so-called target values forphosphorus of 0.16-0.2 mg/l total-P, which were deter-mined in a "Study on the effects of, and quality targets for,nutrients in running water" carried out on behalf of theGerman Department of the Environment.Eutrophication of water cannot be averted with such a pol-lution. Signs of eutrophication are to be seen in the largerrivers all over Germany, particularly in lowlands and inrivers which have dams in their course or flow throughlakes. In the rivers Spree and Havel, large amounts of algalbiomass are measured every year. In summer 1990,exceptional algal mass development was to be seen forthe first time in the tidal region of the River Elbe also.The cause could be improved light conditions, e.g. thedecrease in turbidity and pollutants resulting from theclosedown of several paper factories.In addition to these reasons, the continuing high influx ofnutrients must be seen as a fundamental cause. The tar-get values for the nutrient phosphorus, for example, areexceeded by about 60% in selected running water loca-tions in Germany. Because of this, it is absolutely necces-sary to further reduce the target limits to 0.05-0.15 mg/ltotal-P.Endeavours to bring about improvements in the area of"diffuse sources" (i.e. the area of agriculture and livestock)have achieved only little success, however, both for run-ning waters and for standing waters. The pollution hasindeed been reduced from an absolute point of view, butbecause of the great improvement in the area of pointsources, its share has increased to approx. 40%.

* Eutrophication is to be understood as the increasing enrichment of bod-ies of water with plant nutrients and the progressive decay of the waterdue to the luxuriant plant growth caused by them with its results on thetotal balance of the body of water concerned. Elevated concentrations ofphosphorus compounds in particular, but also of nitrogen compounds,are held responsible for the eutrophication process. But lakes also agenaturally, without anthropogenic influences. The difference is merely thatthe time required for ageing processes is reduced by man by a factorof 103.

17



In 1985 one still assumed that each person passedapprox. 4 g phosphorus into running water via the domes-tic sewage per day. This amount has probably nowadaysbeen reduced to 2 g phosphorus per person per day. For atown with over a million inhabitants, such as Hamburg, thisamount adds up to a total of approx. 4 metric tonnes phos-phorus in the total waste water.Taking a possible removal rating of approx. 90-95% in thewater treatment plants, we must assume that 0.2-0.4 ton-nes of phosphorus is discharged into the River Elbe daily.The discharge of waste water into standing water is out ofthe question because of the particular conditions there.The inputs of nutrients from the so-called diffuse sourcesare, however, not inconsiderable and they accelerate thenatural eutrophication processes.The continuous input of plant nutrients leads to an everincreasing spiral of plant growth and the irreversibleprocesses of seasonal (climate-caused) oxygen deficits inthe hypolimnion near to the sediment associated with it.The study initiated by the OECD to establish a eutrophica-tion prognosis for lakes resulted in the finding that olig-otrophic conditions result at a P-concentration of ≤ 8 µg P/l,mesotrophic at ~ 25 µg P/l and eutrophic at ~ 80 µg P/l.These values are based on a calculated probability of80%.The concentration of nutrients which is available at thebeginning of a "lake year" (spring overturn) determines thenamed processes. As can be seen from the followingTables 1 and 2, there are relatively high phosphate valuesin the surface water at the end of the winter stagnation andcorrespondingly high values in the deep water at the endof the summer stagnation.The almost uniform values at the end of the spring turnover(Table 2) give here a good impression of the eutrophication

condition of the lake. Further inputs of phosphorus wouldstrengthen the seasonal phytoplankton growth phases(see Fig. 9) and, on a long-term basis, limit the aerobicdecomposition processes of the reducers, as the oxygencapacity in the deep water near to the bottom is limited dur-ing the stagnation phases.The binding of orthophosphate in the form of water insolu-ble iron-II-phosphate complexes (FePO4) in sedimentunder oxidizing conditions in deep water near to the sedi-ment, and its liberation under oxygen deficit conditions,was described in section 2.2.4.In our measurements we only take the orthophosphate(PO4

3-) into consideration.This value allows conclusions tobe drawn on the total phosphate value, and is also one ofthe 8 parameters of the BACH examination system.

2.2.8. Ammonium (NH4+) value

Alongside phosphate as outstanding growth limiting factor,elevated concentrations of nitrogen compounds also playa part in connection with the determination of water quali-ty. The input of nitrogen compounds in the form of ammo-nium and nitrate compounds is also named "plant fertiliza-tion".Nitrogen is taken up by plants from water in the form ofammonium (NH4

+) and nitrate (NO3-). The molecular nitro-

gen (N2) which diffuses into water through the boundarysurface water-air, or which is formed in water by bacteria(denitrifiers: bacteria utilize the oxygen present in nitratesfor their respiratory processes and thereby form molecularnitrogen ), cannot be directly utilized by plants for theirmetabolic processes. Only some nitrogen-binding bacteriaand blue-green algae can do this, but these processes areof no importance in this connection.

Jan Feb March April May June July Aug. Sept. Oct. Nov. Dec.

35 36 62 64 11 10 1 3 1 4 22 85

Table 1.Seasonal variations in values measured for orthophosphate in the surface water of a dimictic lake, given in µg/l PO4

3-

(Lake Constance)

0 m 10 m 30 m 50 m 100 m

September 1 1 66 73 79April 69 67 69 72 76

Table 2.Depth profile of orthophosphate concentration of a dimictic lake, given in µg/l PO4

3- (Lake Constance)

18



Ammonium and nitrate are formed during the bacterialdegradation of proteins, i.e. during the decomposition ofdead organisms (degradation of the protein via polypep-tides to amino acids) or of excretory products urine andfaeces (with the nitrogenous intermediate products ureaand uric acid). As can be seen from Fig. 10, the proteindegradation processes down to the intermediate products

ammonia (NH3) or ammonium (NH4+) are carried out by

various microorganisms, which thereby consume a lot ofoxygen. The concentration of ammonium is an importantindication of the pollution of the water. BACH took this factinto consideration by giving it a relatively high weightingfactor (0.15). The course of the ammonium evaluationcurve (Fig. 1) is very similar to the curve for phosphate; theindex spans almost 80 points in the range from 0 mg/l to2 mg/l. Useful ammonium values can only be determinedwith a relatively sensitive measuring methodology.Ammonium is not only a fertilizing factor, but also stands ina pH dependent equilibrium with ammonia, which is astrong cytotoxin and so of special significance to the sizeof the fish population in a body of water. Ammonium saltssplit up as follows in water:

NH4+ + OH- —> NH3 + H2O

19



The toxic effect of the ammonia complex greatly increasesat pH values above the neutral point. Fish find optimalhabitat conditions, for example, in the alkaline region fromabout pH 7.8 to pH 9.3. They therefore seek this region.This, however, is very problematical for them at highammonia concentrations, they are "deceived". As in suchpolluted water the oxygen content as a rule is also rela-tively low, these two parameters cumulate to give theirresult, which is frequently mass death of fish.Values: Unpolluted surface water has an ammonium con-tent of less than 0.1 mg/l the whole year long. In extreme-ly polluted bodies of water, values above 10 mg/l havebeen measured.The target values given in the "Study on the effects of, andquality targets for, nutrients in running water" are forammonia 0.025 mg/l and for total ammonium, 0.16 mg/lNH4-N for salmonid waters and 0.31 mg/l NH4-N forcyprinid waters.In contrast to the input of phosphorus compounds, there isa distinctly lower tendency to decrease for nitrogen com-pounds.It must be rated as positive that the pollution with ammoni-um has been distinctly reduced, also in comparison withthe total nitrogen pollution. This is predominately thanks tothe equipping of waste treatment plants with nitrification. Inview of the official regulations presently in force, one hopesthat the denitrification procedure will bring a distinctimprovement in future.

2.2.9. Nitrate (NO3-) value

Nitrate concentrations in water are, as already explained inthe previous section in connection with ammonium, depen-dent on the diverse total nitrogen inputs from diffuse andpoint sources.A look at the nitrogen cycle (Fig. 10) shows that ammoni-um is not the only form in which nitrogen is taken up byplants. In the nitrification process, ammonia can be oxi-dized up to nitrite and further to nitrate. The genera of bac-teria responsible for these conversions are Nitrosomas (forthe step from ammonia to nitrite) and Nitrobacter (for thestep from nitrite to nitrate). These photoautotrophic generaof bacteria (which are primarily independent of the energy-rich carbon compounds produced by plants during photo-synthesis) obtain the amounts of energy necessary fortheir metabolism from exothermic reactions taking place inthe oxidation processes they catalyze. And they require alot of oxygen. For example, approximately 4.6 g of oxygenare consumed in the oxidation of 1 g ammonium nitrogen(NH4-N). When conversions are carried out on a larger-scale, an oxygen deficit results in the body of water.In the self-purification processes in running water whichare highly polluted by biologically degradable substances,oxidation processes carried out by Nitromonas to formnitrite can result in an accumulation of this, because of thehigh initial concentration of ammonium/ammonia. Nitritehas a toxic effect on fish, and this effect is strengthened bythe lack of oxygen resulting from its formative process.Values of 0.2 - 2.0 mg/l are already characteristic of cont-

aminated water. In addition, when the oxygen deficit is toolarge, bacteria of genus Nitrosomonas can no longer per-form the conversion process which is vital to them, theirpopulation crashes. Further degradation of the intermedi-ate organic metabolic products can only take place anaer-obically, whereby the water starts to stink because of theputrefactive gases which are thereby liberated.When the oxygen concentration is sufficient, on the otherhand, the nitrite is oxidized to nitrate in the further courseof the self-purification route. Should the oxygen content notbe sufficient for these processes, nitrite can accumulateand cause changes in the natural habitat communities(see 2.2.10.).The nitrate which is present in large amounts at the end ofthese decomposition processes is responsible for strongplant growth in the polluted section of the body of water. Inrunning water, the natural condition is attained again withthe sinking of the phosphate value.In a lake, the same processes take place in principle, butwith the differences that, on the one hand, once contami-nating factors have been brought in, they almost com-pletely remain in the body of water and circulate in the pro-duction processes, and on the other hand, because of theoxygen conditions caused by the stratification conditions,an anaerobic decomposition of pollution indicators isimpossible, at least in phases.In unpolluted surface water, a nitrate-nitrogen content(NO3

--N) of approx. 1 mg/l can be measured throughoutthe year. The data for the BACH system evaluation curvefor nitrate can be taken from Fig. 1.High nitrate concentrations in water are not directly criticalfor aquatic organisms – and not for fish.For the "quality target for the conservation product drinkingwater supply from surface waters" (EC Guidelines), the(NO3

--N) value is given as 5.7 mg/l. The limiting value fornitrate given in the German Drinking Water Regulations is50 mg/l NO3

- (= 11.4 NO3--N mg/l).

Higher nitrate values in drinking water endanger humanhealth (e.g. "blue babies" in the case of infants). Whendrinking water containing nitrate is regularly consumed(nitrate is also present in higher concentrations in vegeta-bles, for example), the effective load of nitrate should bechecked (index value: approx. 200 mg/day).The relatively high nitrate concentrations in ground waterand surface water (on average, approx. 80% of the waterin running waters comes from ground water, and only 20%from surface draining) are predominately to be related todiffuse sources (particularly from areas used for agricul-ture). It is estimated, that on average for Germany, an orderof magnitude of 100 kg/ha excess nitrogen from theN-account for agriculturally utlilized areas can be reckonedwith yearly. The increasing automobile traffic also con-tributes to the general negative nitrogen balance sheet.The exhaust components known as nitrogen oxides notonly play their part as acid-formers (nitrous acid HNO2 andnitric acid HNO3) but also have a demonstrable increasingsignificance as plant fertilizers. The associated input ofnitrogen, for example in the forests, is considerable.

The excesses of nitrogen are usually mostly find their way,after being washed out, into seepage water and groundwater in autumn and winter (according to the precipitation),and subsequently into rivers. Here, part of the nitrate isreduced and gassed out into the atmosphere as molecularnitrogen, so that the nitrogen concentration does not havethe same high value as in the ground water, and is there-fore mostly distinctly below the limiting values given in theDrinking Water Regulations. Only time will tell if thedescribed development trend will continue.A positive aspect of high nitrogen concentrations in bodiesof water should not go unsaid: With higher pollution, ahigher nitrate value can lead, in connection with denitrifi-cation in oxygen-deficient sections of a body of water, tothe provision of large amounts of oxygen for aerobicprocesses.

2.2.10. Nitrite valuesNitrite is not detectable in clean, unpolluted waters.It is produced both by oxidation processes (from NH4

+)and by reduction processes (NO3

-), in connection with nat-ural conversion and decomposition processes.The microbial oxidation of ammonium to nitrite and nitrate(nitrification) consumes in part large amounts of oxygen,which can lead to a considerable strain in the context of theoxygen content of a body of water.As already explained in section 2.2.9., during the self-purification processes in running water, when this is highlypolluted by biologically degradable substances, the highinitial concentration of ammonium/ammonia can result inan accumulation of nitrite formed in the oxidation process-es carried out by Nitromonas. Nitrite has a toxic effect onfish, and this effect is strengthened by the oxygen defi-ciency resulting from its consumption in the formativeprocess of the nitrite.Values of 0.2 - 2.0 mg/l already characterize contaminatedwater.At higher concentrations, nitrite must be considered as afirst step towards cancerogenic N-nitroso compounds(nitrosamine).When the oxygen deficiency is too large, bacteria of genusNitrosomonas can no longer perform the conversionprocess which is vital to them, their population collapses.Further degradation of the intermediate organic metabolicproducts can only take place anaerobically, whereby thewater starts to stink because of the putrefactive gaseswhich are thereby liberated.The following values have been set as quality targets fornitrite concentrations for aquatic habitat communities, forexample:

Salmonid:Water < 10 mg/l Cl- –> 0.03 NO2-N and water > 10 mg/l Cl

-

–> 0.02 NO2-NCyprinid:Water < 10 mg/l Cl- –> 0.06 NO2-N and water > 10 mg/l Cl

-

–> 0.04 NO2-NThe limiting value for drinking water given in the GermanDrinking Water Regulations for nitrite is 0.1 mg/l. The aver-age value over the year 1989 for drinking water from theHamburg Waterworks was ten times less (0.01 mg/l).

2.2.11. pHThe pH is an essential parameter for the complete descrip-tion of a body of water. It is primarily a measure of the con-centration of hydrogen ions, and so shows if the water con-cerned has an acidic, neutral or alkaline character. Fromthis, and in connection with a series of other parameters(including conductivity, ammonium/ammonia, alkalinity/carbonate hardness), various reactions result, which ontheir part have an influence on the habitat conditions of theorganisms in the body of water concerned.The degree of dissociation of pure water is very low. It cansplit (dissociate) to give positively charged hydrogen ionsand negatively charged hydroxyl ions:

H2O —> H+ + OH-

H3O+ + OH-

Only 1/10000000th (1·10-7) of the water molecules are dis-sociated. This means that, in 107 litres (= 10.000 m3) ofwater, 1 mol H+ ions (1.008 g) and 1 mol OH- ions(17.007 g) are present. These numbers make very clearhow small the dissociation of pure water itself is. When werelate these stated dimensions to 1 litre of water, we obtainthe hydrogen ion concentration per litre of water (the num-ber of moles of active hydrogen ions per litre of water). Asthis is a very small number, it is purposeful to define themass of hydrogen (= potentia hydrogenia), i.e. the pHvalue, as the logarithm of the reciprocal value of the con-tent of free hydrogen ions.

Under neutral conditions, the hydrogen ion concentrationin water is 10-7.The pH is then 7. Water offers ideal habitat conditionswhen it has a pH value which is around the neutral point(pH 6.5 - pH 8.0).This is also justly considered in the BACH pH evaluationcurve (Fig. 1).The pH of bodies of water has been increasingly loweredin the past by acid rain and by the input of acid formers intothe soil and the water.The cause of this development can be attributed to theemissions into the atmosphere associated with the utiliza-tion of fossil energy for domestic heating and transport,and by industry. In areas which have relatively clean air,rainwater usually has a pH of about 5.6. This is alreadyquite a low value, and can be explained by the naturaloccurrence of CO2 in the atmosphere. The carbonic acidformed by reaction with water is indeed a weak acid, buton passing into a body of water nevertheless leads to anincrease in the hydrogen ion concentration and so to a low-ering of the pH.As a rule, however, the normal buffering capacity (see2.2.12. Alkalinity) neutralizes the hydrogen ions which arebrought in (for example, water which is high in calcium car-bonate and has a pH between 7 and 8 can bind carbonicacid as hydrogen carbonate for use in photosynthesis).The increasing quantities of CO2 which are emitted in theexhaust gases of the worldwide motor car traffic, and alsothe acids formed in the atmosphere from the harmful gascomponents SO2 and NOx (sulphurous acid, sulphuricacid, nitrous acid, nitric acid) have however in the pastalready led to pH values in precipitation which were of aproblematic nature even for bodies of water with goodbuffering capacities. In the Netherlands, for example, thelowest average precipitation pH of the world was mea-sured, pH 3.8. In Germany there are already a number oflakes (including Lake Arber in the Bavarian forest) whichhave become fish-free because of acidification to belowpH 5. Bodies of water in regions with poorly buffered soil

(lime deficient granite, gneiss or mottled sandstone) fre-quently have alarmingly high aluminium contents becauseof their low pH (metals such as aluminium, copper, cadmi-um and lead pass into solution to an increased extentunder these conditions), which make them no longerusable as drinking water.

2.2.12. Alkalinity valueThe alkalinity is defined as the quantitative ability of anaqueous environment to react with hydrogen ions. InGermany, where the term alkalinity was previously notcommonly used, various other terms such as alkali con-tent, acid capacity, carbonate hardness, the m-value andacid binding capacity were used*.The alkalinity value provides information on the hardnessof the water. It is very closely connected with the pH(2.2.11) and the gross primary production (2.2.6) etc., andwill only be presented here in connection with the differentloadings of water**.The hardness of a body of water is due to calcium andmagnesium compounds (total hardness). Part of thesecompounds are in the form of carbonate and hydrogencarbonate (carbonate hardness / CH***).

pH = log 1[ H+ ]

= - log [ H+ ]

21

2


* This term has been commonly used outside of Germany for some time,and is now recommended in the new DIN EN ISO 9963-1. The terms"acid binding capacity", "acid capacity" and "m-value" are customarybecause the hydrochloric acid consumed is experimentally determined.The m-value is calculated from the determination of the proportion ofhydrogen carbonate by titration (one tenth normal hydrochloric acid per100 cm3 of the water sample) against the indicator methyl red to the endpoint at pH 4.3. At this equivalence point, there is no hydrogen carbon-ate in equilibrium, all is present as carbonic acid. The "acid capacity" isquantitatively apparent from the volume of hydrochloric acid used.** The hardness of the water plays a part in various connections (e.g."boiler scale" as by-product of the hardness formers in boiled hard water,"grey film" as a result of using household soap in hard water, the condi-tion of the tap water with respect to the lime-carbonic acid equilibriumwith a view to the preservation of the piping).*** The carbonate hardness / CH is also known as temporary hardness,as it can be removed by boiling: Removal of CO2 and formation of boilerscale. The remaining portion of the hardness, the non-carbonate hard-ness / NCH (caused, among others, by sulphate, nitrate and chlorideions) is also known as permanent hardness, as it cannot be removed byboiling.

Measurement methods and parameters

Carbonate hardness is often given, in relation to and incomparison with the total hardness, in °d (°dH). The des-ignation as "German degree of hardness" (°d) is custom-ary, the recording as CaO is difficult to understand in con-nection with this theme, as CaO is not a constituent ofwater. The relation to the hardness formers (concentrationof the quantities of calcium and magnesium), calculated ascalcium leads to the conversion modalities:

1°d = 10 mg/l CaO = 0.178 mmol/l CaO or Ca = 0.357 mmol/l HCl (1Ca2+ =̂ 2H+)1°d = 0.357 mmol/l HCl 1 mmol HCl = 2.8 °d

It is therefore determined by the number of alkaline earthions of calcium and magnesium, whose salts are washedout of chalky rocks by rainwater and are then brought intothe various bodies of water. It is so the geological condi-tions of the source and seepage regions which primarilydetermine the hardness of a body of water. The carbonateand hydrogen carbonate compounds represent on the onehand an effective buffering system in the body of water (thepH correlates with the carbonic acid content of the water),and on the other hand , when there is an excess of CO2and so of carbonic acid, make the reversible binding of thisso important plant nutrient possible. A condition existsbetween the formation and the decomposition of calciumhydrogen carbonate which is held in equilibrium by theaccompanying free carbonic acid present.

H2CO3 –> H++ HCO3

- –> 2 H++ CO32-+ Ca2+–>Ca (HCO3)2

23

3Description of the quality classes of running waters


THE QUALITY CLASSES OF RUNNING WATERS

Quality class I:Unpolluted to very slightly polluted (oligosaprobic)Sections of water with clean water, always almost saturat-ed with oxygen and nutrient-poor; low content of bacteria;moderately densely populated, predominately with algae,moss, free-living flatworms and insect larvae; when cool insummer1), spawning water for salmonides.Spring-fed brooks and very lowly polluted headwaters ofrunning water which is cool in summer belong in general tothis quality class. Such water is mainly to be found inunpopulated or only thinly populated areas with little or noland utilization. The waters are fast-running, the water isclear, the bottom is predominately stony or beachy, seldomsandy or consisting of fine mineral sediment.The O2 content lies near to the saturation value (between95-105% of O2 saturation),the water is relatively nutrient-poor, the organic load is low (consumption < 1 mg/l O2),ammonium (NH4

+) is only present in trace amounts.The population with invertrebrate animals (macrozooben-thos) is often species-rich, but with low individual density.In spring-fed brooks, alongside snails of genus Bithynella,free-living flatworms of genera Polycelis felina andCrenobia alpina, as well as stoneflies of genus Leuctra,are frequently found. In the uplands, the life communitiesare richer in species, alongside mayflies of genera Baetis,Ephemerella, Epeorus and caddis worms such asOdontocerum albicorne, Philopotamus spp., Silo spp.,larger stonefly larvae such a Brachyptera seticornis andB. risi, Dinocras cephalotes and Perla marginata are found.If moss carpets are present, they are inhabited by variousbeetles, e.g. Elmis latreillei (in mountains), Esolus angus-tatis or Hydraena species. In lime-deficient regions, thesestreams are threatened by acidication.The saprobic index is below 1.5.The watercourse is a spawning zone for salmonides, andis often populated by Cottus gobio.

Quality class I-II:Slightly polluted (oligo- to betamesosaprobic)Sections of water with little inorganic nutrient input, andorganic load without any drain of oxygen worthy of men-tion; densely populated, mostly with a large diversity ofspecies; when cool in summer1), salmonid water.

With the waters classified here, we are dealing mostly withheadwaters in mountains and uplands, but also with natur-al bodies of water in larger forest regions, in lowlands suchas the Lüneburg Heath or the Mecklenburg Lake District.These waters are generally also cool in summer, the waterlimpid. The bottom is, according to the velocity of flow,stony to beachy in the uplands or beachy to sandy in theplains, whereby fine sediment which occurs shows only alow content of oxygen consuming organic matter.The oxygen content lies in the region of saturation, lowdeficits (> 20%) and small fluctuations can occur duringthe diurnal turn. The nutrient contents are at most slightlyelevated, the drain (BOD5) is low (≤ 2 mg/l O2). Ammonium(NH4

+) is mostly only present in trace amounts.According to the substrate composition and the shading,individual moss carpets or filamentous algae up tospecies-rich populations of higher aquatic plants are to befound as submerged vegetation. These never completelycover the surface. Alongside moss, moderately dense pop-ulations of higher aquatic plants, e.g. Callitriche spp. orRanunculus peltatus are to be found in flat land streamswith little gradient.The macrozoobenthos is species-rich and forms richlystructured, dense life communities.Whereas in waters withlarger gradients, mostly hard substrate inhabitants pre-dominate, in flat land burrowing species are also found.Typical representatives of the fauna are the free-living flat-worm Dugesia gonocephala, the mayfly nymphs of generaEcdyonurus, Paraleptophlebia submarginata andRhitrogena semicolorata. Alongside these, stoneflies, e.g.Leuctra niger or Perla burmeisteriana are to be found.Many species of caddis worms are also present; typicalindicators are Oligoplectrum maculatum, Lepidostoma hir-tum, Silo pallipes, Plectrocnemia species.In this quality class in lowland waters, larvae of the drag-onfly Cordulegaster boltoni and of the mayfly Ephemeradanica are to be found as burrowing species, in larger bod-ies of water also the large mussel Unio crassius.The water is a spawning zone for salmonides.The saprobic index is in the range of from 1.5 to < 1.8.

Quality class II:Moderately polluted (betamesosaprobic)Sections of water with moderate pollution and good supplyof oxygen; very large diversity of species and individualdensity of algae, snails, small crustaceans, insect larvae;aquatic plant stand can cover larger areas; species-richfish water.Belonging to this are stretches of water with moderate con-tamination by organic substances and their decompositionproducts, but also the lower courses of larger rivers andthe naturally nutrient-rich, slowly flowing and summer-warm lowland streams. The bottom is stony to beachy inthe mountainous regions, but in places, deposits of fineorganic sediment or black speckled undersides of stonescan occur. In the lowland streams and rivers there is pre-dominately sandy-beachy sediment, larger stones are sel-dom, in contrast to most upland streams.

1) Summer-cool running waters are found predominately in uplands andmountainous country. Their natural water temperature is up to 20oC.Summer-warm running waters are predominately lowland streams andlarger running waters with temperatures of approximately 25oC.

24

3 Description of the quality classes of running waters


Fine organic sediment is held in places. A corresponding-ly low flow-adapted hypolithic population has developed inthe animal life community in such watersStrong growth of higher aquatic plants occurs particularlyin slow running waters with little shade, larger runningwaters are distinctly turbid in summer due to the develop-ment of phytoplankton. The oxygen balance presents itselfcorrespondingly. Whereas the running water in mountain-ous and hilly country can permanently show slight oxygendeficits – without dropping below values which are criticalfor fish, however – distinct diurnal rhythms with oxygensupersaturation in the afternoons and deficits towards themorning are typical for lowland waters.Ammonium nitrogen concentrations mostly lie below0.5 mg/l NH4

+-N. The biochemical oxygen demand in5 days lies mostly below 5 mg/l, higher values are onlymeasured in phytoplankton-rich waters.The biocoenosis of the macrozoobenthos is quite rich inspecies, the biomass is large.With increasing share of organic sediment, the share ofmud inhabitants markedly increases, in addition, anincreasing organic drift leads to a stronger presence of fil-tering forms.Typical indicators in streams in mountainous country arethe cap-like river limpet Ancylus fluviatilis, mayfliesEphemerella ignita, Heptagenia flava and Heptagenia sul-phurea. Reliable indicators are also the caddis fliesBrachycentrus subnubilus, Anabolia nervosa, Rhyacophilaspp., Polycentropius spp. and Goera pilosa. In the larger,plankton-rich running waters, filtering life form types arefound on hard substrates, e.g. freshwater spongesEphydatia fluviatilis or Spongilla lacustris or, in fine sedi-ment, brozoa of genus Plumetella as well as macro mus-sels of genus Unio. Freshwater shrimps Gammarus roeseliis frequently to be found within its range, next to mayfliesof families Baetidae and Potomanthus luteus. In plant-richsegments, dragonfly larvae of genera Calopteryx, Lestesviridis or Phyrrhosoma nymphula belong to the typicalmacro fauna. Under the caddis worms in these waters, fil-tering species such as Cheumatopsyche lepida, Ecnomustenellus or Pyschomyia pusilla dominate. Besides these,typical grazers such as the snails Viviparus viviparus andTheodoxus fluviatilis, in greater bodies of waterBathyomphalus cocortus and in smaller bodies of waterValvata piscinalis are frequently found.These waters as a rule have good fish stands, dependingon the region and size of the body of water, they belong tothe lower salmonide or to the cyprinide region.The saprobic index is in the range of from 1.8 to < 2.3.Water quality class II is the political aim of water conser-vation in many states. From the ecological point of view,however, this quality class does not show the water typicalspecies composition in mountain streams.

Quality class II-III:Critically polluted (betameso- to alphamesosaprobic)Sections of water whose load of organic, oxygen-consum-ing matter has brought about a critical condition; death offish as a result of oxygen deficiency is possible; decline inthe number of species of macroorganisms; certain speciestend to mass development; filamentous algae frequentlyform large, surface covering stands.The waters of this quality class are markedly changed bythe effect of the decomposable organic matter. In fast-run-ning waters, the undersides of stones are black or spottedblack from the formation of black iron sulphide (FeS).Sludge layers are frequently only oxidized at their surfaces.Underneath there is mostly a profound, black-colouredanaerobic sludge sediment. When dense plant stands arepresent, particularly in slower running water, then theyhave turbidity attached to them. The water is turbidbecause of either bacteria or organic matter, or a distinctvegetation colouration due to planctic algae makes itselfnoticeable.The O2 saturation is either permanently in the range of amarked deficit (up to 50% saturation) or, during the vege-tation period, is characterized by strong fluctuations in diur-nal rhythm, whereby in the early morning hours the mini-mum is only a few mg/l O2. The biochemical oxygendemand (BOD5) lies above 5 mg/l O2. The ammoniumnitrogen concentration often reaches 1 mg/l NH4

+-N.The animal colonization already exhibits marked deficits inthe species composition. Alongside the stonefly larvae, themayfly larvae and the caddis worms are also missing,except for a few exceptions. On the other hand, somespecies, in particular grazers and detrivores, are present invery high population densities. Typical indicators in fast-running water are, alongside the free-living flatwormPlanari torva, the snails Bithynia tentacula and Physa fonti-nalis, as well as the leeches Erpobdella octoculata andGlossophonia heteroclita. One very frequently finds thewater slater Asellus aquaticus, colonies of ciliates, mostlygenus Stentor sp. are partly visible to the naked eye. Inslowly running water or dam regulated waters, autotrophicproduction determines also the food production in thesummer months. Besides the indicators named above, onealso then finds increasingly filter feeders such as the bro-zoa Plumatella fungosa, in plant stands the snails Radixovata and Potamopyrgus antopodarum, the wormsStylaria lacustris, Nais elinguis, on muddy sediment alsoAelosoma spec.. The leech Helobdella stagnalis and theorb mussel Spaerium comeum are also widely distributed.The fish stand is made up predominately of cyprinides, theanaerobic sediment can stop the propagation of soil-spawners.The saprobic index is in the range of from 2.3 to < 2.7.

25

3Description of the quality classes of running waters


Quality class III:Highly polluted (alphamesosaprobic)Sections of water with high organic, oxygen-consumingcontamination and mostly low oxygen content; layers ofanaerobic sludge locally; colonies of filamentous sewagebacteria and sessile ciliates surpass the presence of algaeand higher plants; only a few animal macroorganismsinsensitive to oxygen deficiency, such as leeches andwater slaters, are present, at times in very large numbers;a periodic death of fish is to be expected.Waters of this quality class are given their character by theintensive heterotrophic processes and the resulting highoxygen deficit. There is a distinct bacterial turbidity in thewater. Hard substances are coated with a thick film of bac-teria.The undersides of stones and fine sediment are coat-ed black by iron sulphide, hydrogen sulphide (H2S) is lib-erated from mud layers when they are stirred. As a rule,higher aquatic plants are missing, filamentous algae andcoatings of cyanobacteria (blue-green algae) can appearin huge numbers.The oxygen balance is permanently in deficit, the minimumlies below 2 mg/l O2, the content of organic matter causesa biochemical oxygen demand of up to 10 mg/l O2, ammo-nium nitrogen concentrations of 1 mg/l NH4

+-N areexceeded on a fairly long-term basis. In phytoplankton-richwaters, photosynthesis drains CO2 from the water, where-by the pH increases. At higher pH values or water temper-atures, there is therefore often a formation of toxic ammo-nia (NH3).The habitat conditions in waters of this pollution level havebeen worsened so far, that only few macroorganisms,those which can tolerate the low O2 concentrations, arepresent in this water and can be used as indicators.Besides the snail Physella ocuta, these are Chironomusthummi, Proasellus coxalis and, in slowly running waters,the oligochaetae Lumbriculus variegatus and Pristinaspec.. On the other hand, there is a whole series of goodindicators, which are also widely distributed, among theheterotrophic microrganisms, particularly among the fla-gellates and ciliates (Ciliophora).Fish populations often cannot permanently exist, frequent-ly the younger generations are missing.The saprobic index is in the range of from 2.7 to < 3.2.

Quality class III-IV:Very highly polluted (alphameso- to polysaprobic)Sections of water with extensively limited life conditionsbecause of the very high contamination with organic, oxy-gen-consuming matter, often augmented by toxic effects;at times, total lack of oxygen; turbidity from suspendedmatter in sewage; expanded anaerobic sludge layers;densely populated by ciliates, bloodworms or sludgeworms; decrease in filamentous sewage bacteria: Fishonly to be found as an exception and not for long duration.

The quality of the waters as ecosystems are very greatlychanged by the effect of decomposable organic matter andthe results of the aerobic and anaerobic degradation. Thebottom of the body of water is covered by anaerobicsludge, higher submersed plants are missing, the water iscoloured or rendered turbid by wastewater and bacteria,and often smells of H2S, there is a visible gas formation inthe sediment (methane, hydrogen sulphide).Oxygen is at times only present in such waters in traceamounts.The O2 saturation deficits are as a rule very high.The BOD5 lies above 10 mg/l O2, the ammonium nitrogenconcentration exceeds 1 mg/l NH4

+-N on a fairly long-termbasis.The macroorganism population is extremely poor inspecies, typical thereby is the development of great num-bers of Tubifex spec. and/or larvae of midges of theChironomus thummi- and Chironomus plumosus-groups.Solid substrates (wood, stone) is often coated with a thickfur of the sewage bacteria Sphaerotilus and the sewagefungus Leptomitus lacteus. On the surface of the sludgeand in the blue-green coatings of cyanobacteria (blue-green algae) there is a rich fauna of unicellular organisms,predominately mastigophora (flagellates) and ciliophora(ciliates), which allow a good indication on the basis ofmicroscopic results. Toxic effects can be frequently deter-mined - see the special symbols in the legend to the qual-ity map.The saprobic index is in the range of from 3.2 to < 3.5.

Quality class IV:Excessively polluted (polysaprobic)Sections of water which are excessively contaminated byorganic, oxygen-consuming wastewater, putrefactiveprocesses predominate; oxygen over longer times presentonly in very low concentration or completely lacking; set-tlement mainly by bacteria, flagellates and free-living cili-ates; fish are missing; with high toxic contamination, bio-logical desertion.Waters of this class carry highly turbid water. Constituentsof the water and decomposition products form sedimentand water can lead to considerable odour nuisance. Thebottom of the body of water is covered with anaerobicsludge and permanently anaerobic. Colouration from sul-phur bacteria is frequent; fungi developments (Fusariumaquaeducutum) cover complete surfaces in places. Higherplants are missing, autotrophic microorganisms, e.g. sul-phur bacteria, can occur in great numbers. The oxygencontent lies on a long-term basis below 1 mg/l O2, the sed-iment surface is permanently anaerobic, methane andhydrogen sulphide are evolved from the sediment.The bio-chemical oxygen demand (BOD5) lies well above 10 mg/lO2, ammonium nitrogen contents in the range of severalmg/l NH4

+-N are permanently measured.

26

3 Description of the quality classes of running waters


The settlement by macroorganisms is limited extensivelyto diptera larvae of the Chironomus plumosus group andthe family eristalinae. Bacteria and flagellates are the dom-inating microorganisms. The obligate anaerobic sulphurbacteria, flagellates of genera Tetramitus, Trepomonasand Trigonomonas as well as some ciliates (e.g.

Paramecium putrinum) are good indicators. When toxiceffects are determinable, these are displayed with the helpof special symbols (see the legends to the quality maps).Fish are not found in bodies of water of quality class IV.The saprobic index is in the range of from 3.5 to < 4.0.

27

4Description of the trophic levels of running waters


Designation of Brief description Abbreviation Colour the trophic level coding(evaluationsteps)

oligotrophic Production weak because of low availability of nutrients; o dark bluephytoplankton development low the whole year;depth of transparency high because of low plankton density;oxygen concentration at the end of stagnation period still above4 mg/l O2

mesotrophic Production higher than in oligotrophic bodies of water because m light blueof higher availability of nutrients; phytoplankton developmentmoderate with large species diversity and maximum in Spring;average dept

30837 22 gruen spirale 6 9€¦ · theoretical section 1 introduction 2 measurement methods and...

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