CHAPTER - V. It is well established that environmental distrubance. such as pollution induces changes in structure and function of

Transcription

1 CHAPTER - V 5. WATER POLLUTION INDICES It is well established that environmental distrubance such as pollution induces changes in structure and function of the biological system and also changes the physico-chemical characteristics of the natural water quality. For the detection and evaluation of water pollution, the water pollution indices are commonly used. The indices are characterised into two parts : the physico-chemical indices and biological indices. Physicochemical indices are based on the values of various physicochemical parameters in a water sample while the biological indices are derived from the biological information. These indices are aimed at providing numerical version of the biological information and also physico-chemical information of the water. In this study the following two indices are taken into consideration for biological information based on algae and one index is considered for physico-chemical information for assessment of water quality of the Bharalu Stream and Deepar beel The indices are as follows : (a) Diversity index (i>) (b) (c) Palmer's pollution index (P.P.l.) Organic pollution index (O.P.T.)

2 DIVERSITY INDEX A number of studies have showed the pollution produces striking changes in the biotic community. Some of the species may be unable to tolerate slightest of pollution while few species may persist in reduced coactions and then again certain species may be able to attain greater abundance under the same situation. This causes an imbalance in the system which could be monitored to detect the status of pollution. These structural changes can be quantified numerically and are very useful in assessment of water quality based on the principle that polluted water supports always low diversified flora and fauna while clean water supports high community diversity. The diversity index is calculated from the abundance data of organisms and serves as a very good indicator of pollution. Some of the common diversity indices are given below : (i) KOTHE*S SPECIES DEFICIT INDEX : This index is based on the principle that in a flowing ecosystem the number of species decreases after they are exposed to some pollutant discharge. In this method the number of species of either a particular group e.g. algal or macro invertebrates or of all the group are counted at the polluted and non-polluted points (Kothe, 1962). The index is calculated by using the following formula : Kothe's Species Deficit ( 100) (IKO)

3 152 where, = no. of species at the unpolluted site. A = no. of species at the polluted site. X (ii) GABRIELS BIOTIC INDEX : Since the number of individuals of reducers (R) and consumers (C) are extremely abundant in heavily polluted waters, Gabriel (1946) has proposed the biological index to asses water quality by applying the following formula : lb = ^2 where lb = biotic index R+C (iii) PANTLE AND BUCK'S SAPROBIEN INDEX : Based on degree of Saprobiety ranking, Pantle and Buck (1955) has given the following saprobien index. Ig = ^ S h ^ h 8 = degree of Saprobiety h = relative frequency of each species I = saprobien index. (iv) COEFFICIENT OF SIMILARITY Burlington (1962) used a formula to obtain a coefficient of similarity between two communities as follows : 2 (EP1) c = Pi + P j where Pi = Prominence value of a species at Station i. Pj = Prominence value of the species at Station j. ' = Prominence value of the species common to 1 & j station.

4 153 C -- Coefficient of similarity. (v) CAIRNS AND DICKSON'S SEQUENTIAL INDEX : A sequential comparison index that requires little taxonomic experties was developed to establish relative differences in biotic diversity and water quality by Cairns and Dickson (1971) by following formula : Pj no. of runs no. of specimens (vi) ODUM'S SPECIES PER THOUSAND INDIVIDUALS : It is an excellent index to determine the level of pollution in both lotic and lentic water bodies (Odum, 1971). It is calculated by using the following formula : 01 Total no. of species encountered in the sample Total no. of individuals of all the species x 1000 VII) SIMPSON'S PROBABILITY FORMULA : A useful measure of diversity was proposed by Simpson (1949). He proposed the following formula for calculation of N. (N. - 1) D = J N (N - 1) where N = Total no. of individual Nj = No. of jth species (j = S) (viii) SHANNON AND WEAVER'S FORMULA : The structure of biotic community can be summarised in

5 154 diversity index derived from the information theory. Since some species may be supper abundant, a large probability exists that individuals observed during sampling belongs to a species previously recognised. Thus considerable repeatition of information exists and redundancy is high. Information per individual is low and is reflected in a low index of diversity. The more species present in a community and more equal their abundance, greater the diversity. The diversity index based on information theory was first used by Margalef (1958) to analyse natural communities. This technique equates diversity with information. Maximum diversity and thus maximum information exists in a community of organisms when each individual belongs to a different species. Minimum diversity or high redundancy exists when all individuals belong to the same species. The formula used in calculation of Shannon and Weaver.'s diversity index (1963) is as follows : D = - Epi Log2 pi where D = Diversity index pi= ni/n (Where ni = number of individuals in species ; N = total number of individuals in the sample). This diversity index is widely used in assessment of pollution level. Most of the workers report that the value of this index declines in polluted water. Wilhm and Dorris (1968)

6 155 found that the value of the index declines sharply when mine discharges are confluenced with the river but after some distance when the pollution level comes down due to dilution factor, the value of the index comes back to normal. Trivedi (1980) made an extensive study on the Chambal river at Nagda on planktons. His study showed that the diversity index (Shannon and Weavers) can be correlated with various degree of pollution. The Shannon diversity index of benthic diatoms in a lotic subtropical environment was studied by Prasad and Singh (1982) and the periodicity and inter relationships of this are highlighted. A recent study has been carried out to evaluate the level of organic pollution in Hugli estuary and the diversity index was measured on the basis of Shannon - Weavers method (Ruma Pal et. al., 1992 and Nandan and Patel, 1985b) using Shannon and Weavers diversity index, Acharjee et. al. (1995) worked out the phytoplankton community behaviour in Dighali Beel. For the present study the Shannon and Weaver's diversity index is considered to assess the water quality of the Bharalu Stream and the Deepar beel. Several scientists have proposed the relationship between diversity index (D) and the pollution level of the water bodies as follows : Wilhm and Dorris (1968) proposed the following relationship between diversity index (D) and pollution status. D Condition > 3 Clean water 1-3 Moderately polluted < 1 Heavily polluted

7 156 Staub et. al. (1970) proposed a scale based on their study on the effects of industrial wastes on primary planktonic producers in Mississipi river as follows : D Condition Slight pollution Light pollution Moderate pollution Heavy pollution As scale proposed by Trivedi (1980 and 1981) on correlation of diversity index (D) and the degree of pollution as follows : Condition >4.0 Clean water Very light pollution Moderate pollution <2.0 Heavy pollution In the present study the Trivedi's (1980) proposed scale is considered for evaluation of pollution level in Bharalu stream and Deepar beel water. The values are obtained by using the Shannon and Weaver's diversity index (D) of various sampling stations of Bharalu stream and Deepar beel are shown in the Table Nos. 5.1 and 5.2 and Figs. 5.1 and 5.2 respectively.

8 157 TABLE SHANNON AND WEAVER'S DIVERSITY INDEX (D) OF DIFFERENT SAMPLING STATIONS OF BHARALU STREAM SAMPLING STATION D VALUE I 3.03 II 2.67 III 2.54 IV 2.36 V 1.95 VI 1.50 VII 1.21

9 158 TABLE SHANNON AND WEAVER'S DIVERSITY INDEX SAMPLING STATION OF DEEPAR D OF DIFFERENT BEEL SAMPLING STATION D VALUE I 3.00 II 3.12 III 3.65 IV 2.6

10 159 Diversity Index I II III IV V VI VII Sampling station 6 FIG. 5.1 DIVERSITY INDEX IN DIFFERENT SAMPLING STATIONS OF BHARALU STREAM Diversity Index Sampling station 3D FIG. 5.2 DIVERSITY INDEX IN DIFFERENT SAMPLING STATIONS OF DEEPAR BEEL

11 160 The values of diversity index in the Bharalu stream reveals that the stream is gradually polluted towards downstream due to the gradual increase of organic pollution load. The index value indicates heavy pollution in station nos. V, VI and VII. In Deepar beel water, the values of diversity index are above 3.0 in station nos. II and III which indicate that the water of these two stations are not polluted. While the station I and IV reveals that the water of these two stations are moderately polluted. 5.2 PALMER'S POLLUTION INDEX Palmer (1969) made the first major attempt to identify and prepare a list of genera of algae tolerant to organic pollution. He prepared a list of 60 genera and 80 species tolerant to organic pollution. He also developed Palmer algal genus index for the rating of organic pollution of a water body. In the present body, this index is used for rating the organic pollution of the water bodies. For the calculation of this index, table 5.3 is taken for use. The table provides 20 algal genera most tolerant to organic pollution and a number is assigned to each of them depending on their relative tolerance to pollution. The algae present in the water sample are identified and the genera present from the list are noted. The assigned number scored by each genus are totalled to get the value of algal genus index. Algal pollution indices are also used for detection and evaluation of water pollution (Rai and Kumar, 1980 ; Gunale and Balakrishnan, 1981 ; Nandan and Patel 1983, 1985a, 1986). On the basis of the total score obtained from the

12 161 assigned number to each genus for each sampling station, Palmer (1969) formulated the following pollution index scale for assessment of organic pollution of the water bodies. The pollution index scale is given below : POLLUTION INDEX STATUS OF POLLUTION < 15 Very light organic pollution 15 to 20 Organic pollution >20 High organic pollution In the present study, the Palmer s pollution index of algal genera is taken into account for evaluation of water quality. Pollution index factor is assigned to each genus by determining the relative number of total points scored by each genus of algae. The result of total scored for each sampling station of Bharalu stream and Deepar beel area are presented in the Table Nos. 5.3 and 5.4 and Fig. 5.3 and 5.4 respectively. In Palmer s pollution index of algal genera Anabaena was not considered as pollution tolerant. But from the present study it is observed that this blue green algae can tolerate the organic pollution to a greater extent and the pollution index number of this genus can be fixed at 1. The genus Anabaena was also considered for pollution index and fixed the value at 1 by Nandan and Patel (1986). The total score is recorded in Bharalu stream from Stations I to VII are as follows - 14, 15, 16, 21, 21, 21 and 25

13 162 TABLE POLLUTION INDEX OF ALGAL GENERA (PALMER, 1969) SL.NO. GENERA POLLUTION INDEX SL.NO. GENERA POLLUTION INDEX 1 Anacystis 1 11 Micractinium 1 2 Ankistrodesmus 2 12 Navicula 3 3 Chlamydomonas 4 13 Nitzschia 3 4 Chlorella 3 14 Oscillatoria 4 5 Closterium 1 15 Riormidium 1 6 Cyclotella 1 16 Pandorina 1 7 Euglena 5 1/ Riacus 2 8 Gomphonema 1 18 Scenedesmus 4 9 Lepocinclis 1 19 Stigeocionium 2 10 Melosira 1 20 Synddra 2

14 163 TABLE LIST OF PHYTOPLANKTON AND SCORING OF PALMER'S POLLUTION INDEX OF SAMPLING STATIONS OF BHARALU STREAM PHYTOPLANKTON STATION I STATION II STATION III STATION IV STATION V STATION VI STATION VII Baci1lariophvceae Navicula + (3) + (3) + (3) + (3) + (3) + (3) + (3) Pinnularia Cyclotella + (1) + (1) _ Synedra + (2) Nitzschia - + (3) + (3) + (3) + (3) + (3) + (3) Fragiilaria Gomphonema (1) + CD + (1) Cyanophyceae Oscillatoria + (4) + (4) + (4) + (4) + (4) + (4) + (4) Anabaena + (1) + (1) + (1) + (1) + (1) + (1) + (1) Microcystis (= Polycystis) + (1) + (1) Hiorraidium (1) + (1) + (1) + (1) + (1) Caiothrix Chlorophyceae Ulothrix Ankistrodesmus + (2) + (2) Spirogyra Oedogonium Chlore11a (3) + (3) + (3) + (3) + (3) Closterium (1) + CD Stigeoclonium (2) Euglenophyceae Euglena (5) + (5) + (5) + (5) Fhacus (2) TOTAL SCORE = Present ; - = Absent

15 164 T A B L E L I S T O F P H Y T O P L A N K T O N A N D S C O R I N G O F P A L M E R ' S P O L L U T I O N I N D E X O F S A M P L I N G S T A T I O N S O F D E E P A R B E E L PHYTOPLANKTON STATION - I STATION - II STATION - III STATION - IV Baci1lariophyceae Navicula + (3) + (3) + (3) + (3) Cyclotella + (1) + (1) + (1) + (1) Fragillaria Pinnularia Asterionella Cyanophyceae Oscillatoria + (4) + (4) + (4) + (4) Microcystis (=Polycystis) + (1) + (1) - - Anabaena + (1) + (1) + (1) + (1) Spirulina Hiorraidiura + (1) + (1) - - Calothrix Chlorophyceae ChlorelLa + (3) (3) Chlorococcum Closterium + (1) Spirogyra Straurastrum Micrasterias Ulothrix Desmidium Scenedesmus (4) Cosmarium TOTAL SCORE = Present ; - = Absent

16 165 Palmer Pollution Index Sampling station p p i FIG. 5.4 PALMER POLLUTION INDEX IN DIFFERENT SAMPLING STATIONS OF DEEPAR BEEL

17 166 respectively. This index value indicate that the stream is gradually polluted organically towards downstream i.e. to Station No. VII, high organic pollution is recorded in the Station Nos. IV, V, VII and VII. Similarly, in Deepar beel the total score is recorded in four stations as 15, 14, 9 and 16 respectively. The total score value in Station Nos. II and III reveals that the water quality of these two stations are good while the other two stations i.e. I and IV the total score value indicates the light to moderate organic pollution. 5.3 ORGANIC POLLUTION INDEX (OPI) Accurate and timely information on the quality of water is necessary to formulate a sound public water policy and to implement the water quality improvement programmes efficiently. One of the most effective way to communicate information on water quality trend, is with indices. To evaluate the status of pollution of a water body, water quality yardstick as based on physico-chemical and biological datas are important for water quality management. One such water quality target value as based on physico-chemical data is organic pollution index (OPI). This organic pollution index was proposed by the Indo- Dutch Scientists Dr De Kruijf, Dr. Trivedi and Dr. De Zwart (1992) who jointly made a study on Yamuna river. The significant feature of the index is that a cluster of parameters are considered for evaluation of water quality rather than a single individual parameter. This index is expressed on a scale from 0

18 167 to 100, where 0 indicates the worst imaginable condition, and 100 stands for a totally natural environment which is entirely not influenced by human habitation. But the target level will not necessarily be 100, since human presence add development unavoidably leads to a certain degree of deterioration of the environment. So, the target value for the index may be selected which can also be influenced by regionality e.g. high land rivers or streams versus low land rivers or streams. The organic pollution index is related to the availability of oxygen in a water body and is calculated from monthly measurement on the following parameters : ammonia, biological oxygen demand (BOD), chemical oxygen demand (COD), dissolved oxygen saturation and temperature. The formula used for combining the individual parameter values i.e. OP I = e.[ n 1 Ln (PQI). Wn] 1 n where OPI = The organic pollution index. t h PQI^ = The quality index for the n L parameter, a d imensionless number between 0 and 100, standing for very poor and excellent quality respectively with respect to the parameter under consideration. The quality index is derived from parameter quality curves which are constructed according to target value specified by Bach (1980).

19 168 th Wn = The weightage factor for the n parameter. All the parameters have equal weightage : Wn is equal to 1/n = 1/5. The suggested target value for the organic pollution index is 70 in the final construction of the yardstick (Kruiif, Trivedi and Zwart, 1992). Using the three years of physico-chemical data on Bharalu stream and Deepar beel water the index OPI is calculated and presented in the Table Nos. 5.6 and 5.7 and the suggested target value for this index is 70. It is observed that the OPI values are less than 70 in all the sampling stations of Bharalu stream except station no. 1. Hence, the stream is gradually Vo polluted from Station Nos. II and VII and the Station No. 1 depicts very light pollution. Similarly, in Deepar beel, the OPI values in station nos. I and IV are quite below the suggested target value, which reveal that the water of these two stations are polluted. But the OPI value in the other two stations i.e. II and III are above the suggested target value which indicates that the water quality of these two stations are not polluted. All the three index values of different sampling stations of Bharalu stream and Deepar beel area are presented in Table Nos. 5.8 and 5.9 and graphic presentation for both the water bodies are given in the Figures 5.7 and 5.8. All the indices reveal the same pollution level i.e. gradual pollution towards downstream of Bharalu. Similarly, these indices also

20 169 TABLE ORGANIC POLLUTION INDEX VALUES OF DIFFERENT SAMPLING STATIONS OF BHARALU STREAM SAMPLING STATION OPI VALUE I II 51.2 III IV V VI 8.79 VII 5.54 TABLE -5.7 ORGANIC POLLUTION INDEX VALUES OF DIFFERENT SAMPLING STATIONS OF DEEPAR BEEL SAMPLING STATION OPI VALUE I II III IV 39.4

21 170 Organic Pollution Index Sampling station o p i FIG. 5.6 ORGANIC POLLUTION INDEX IN DIFFERENT SAMPLING STATIONS OF DEEPAR BEEL

22 171 TABLE VARIOUS INDEX VALUE OF DIFFERENT SAMPLING STATIONS OF BHARALU STREAM SAMPLING STATION OPI D PPI I II III IV V VI VII OPI = Organic Pollution Index D = Diversity Index PPI = Palmer Pollution Index

23 172 TABLE VARIOUS INDEX VALUE OF DIFFERENT SAMPLING STATIONS OF DEEPAR BEEL SAMPLING STATION OPI PPI I II III IV OPI = Organic Pollution Index D = Diversity Index PPI = Palmer Pollution Index.

24 173 Index vnluos < &? / <G55? / / a / / T /, / -, C p., X II III IV V VI Sampling station 3 n tz l p p i i OPI FIG. 5.7 VARIOUS INDEX VALUES IN DIFFERENT SAMPLING STATIONS OF BHARALU STREAM VII Index values II III IV Sampling station 5 p p i! o p i FIG. 5.8 VARIOUS INDEX VALUES IN DIFFERENT SAMPLING STATIONS OF DEEPAR BEEL

25 indicate same status of pollution and non-pollution in the various sampling stations of Deepar beel water. 174