Cost of Remediation of the Lujan River (Argentina)

Cost of remediation of the Lujan River

Adonis Giorgi Programa de lnvestigaciones en Ecologia Acuatica (PIEA) - Departamento de Ciencias Bhicas - Universidad Nacional de Lujun-

Argentina.

Abstract

The objective of this study was to estimate the theoretical investment needed for the remediation of river water in the upper and middle course of the LujPn River

(Buenos Aires province, Argentina). Two source of data were used: a) a monthly water sampling in the river over a 27 month period, and b) the Environmental Record of the Municipality of LujPn, where the estimated effluent discharges of the industries and the city of LujPn are registered. The number of days needed to produce the depuration of river water was

estimated relating the biological oxygen demand (BOD) and the chemical oxygen demand (COD) with the dissolved oxygen concentration in water. In addition to this, and assuming that all the effluents that flow into the river do not exceed the DBO standards established by the legislation, the amount of oxygen needed to complete the self-depuration process of the river and the economic

value of this process were estimated. Our results indicate that if industrial and sewage discharges were released in compliance with the existing legislation, the Lujln River has the capacity to depurate these effluents. Nevertheless, the "work" needed to process the effluents under the actual conditions exceeds from 3 to 10 times the real capacity

of the river. To attain a sustainable use of the river, including recreation activities, it is essential to reduce the load of effluents, or to distribute the cost of river remediation among the main pollutant industries.

564 Ecn~ystrmsand Sustainable Devrlopnlrrlt

1 Introduction

The cost of remediation of a resource is related with the contamination cost. This expression refers to the money that should be paid by the industries to reduce the contamination according with their emission of contaminants [l]. Also, this expression is used to state the lose of value of a particular resource by degradation or modification, taking into account the value given to the resource by the population [2], or by the reduction of the price of sale of the resource [3]. This study proposes a method to calculate the costs of remediation and contamination, where both costs are related to the effort necessary to depurate the water of the Lujin river. Particularly, the depuration cost is estimated in the section of the river which flows across the Lujan district. The LujPn river basin occupies an area of 2600 km2 and the main course flows across eight districts (Chivilcoy, Mercedes, LujPn, Pilar, Exaltaci6n de la Cruz, Campana, Escobar, Tigre y San Fernando) with a population of more than 1,000,000 inhabitants. The river is128 km long and it is formed by the union of the Moyano and El Durazno streams in the Suipacha district, and flows into the La Plata River [4]. Mean flow of the river is 5.4 m3/sec, averaging 39.4 m3/sec in the mid-basin [4], and it is mainly fed by local subsurface runoff. Sala [5], differentiated three sections in the Lujin river. The upper course is 40 km long and receives the most important influents (Moyano, Grande, Balta and Ranchos streams). This zone shows scarce drainage and a mean slope of 0.40 &km. The middle course is 30 km long and has a mean slope of 0.83 mkm;it shows a more developed drainage network on the north margin. The lower course shows the lowest slope in the main course and their influents (0.05-0.16

&km) and it is greatly affected by the impact produced by industrial and sewage effluents. Traditionally, cattle farming and extensive agriculture were the prevailing activities in the Lujin river basin, but in the last few decades the increasing urbanization has promoted industrial activity, especially in the low basin. Several industries are installed in the mid-course, and most of them have treatment plants for their effluents. The river also receives the discharge of the sewage treatment plant of Lujin city. Some studies describing the modification of physical and chemical parameters by contamination in the Lujin river have been carried out [6, 7, 8, 9,

101. These studies analyzed the water quality of the Lujin river but not the prospects for its recovery.

2 Methods

Two types of data were used in this study. Firstly, a sampling was carried out in the mid-course of the Lujin river over the course of 27 months, and the variations of pH, temperature, dissolved oxygen, percent of oxygen saturation, ammonia, chlorine, biological oxygen demand (BOD), and chemical oxygen demanu (COD) were recorded. Secondly, we built a registry of all the industries

established in the LujPn district, and we estimated their effluent discharges. The discharge of sewage treatment plant of the LujPn city was also determined. Relating the biological oxygen demand (BOD) and the chemical oxygen demand (COD) with the dissolved oxygen concentration in the river water, it was possible to estimate the number of days needed for the river waters' depuration. In addition, and assuming that all the effluents that flow into the river do not exceed the DBO standards established by the legislation, the amount of oxygen needed to complete the self-depuration process of the river and the economic value of this process were estimated. The economic value of the self-depuration process was calculated relating the oxygen carried by the river with the capacity of oxygen production by a standard machine for water oxygenation [l l] and the energy cost of its operation.

3 Results

The dissolved oxygen carried by the river was calculated considering the mean flow (5 m3/sec) and the mean oxygen concentration of the river (5 mgll); being the oxygen load of 2160 todday. Considering that an air bubble machine has a mean production of 2 kg of oxygen by each kilowatt consumed [l l], and that in

Argentina the cost of each kilowatt for industrial use is 0.15 dollars [12], the mean value of one day of natural depuration work by the river in the mid-course is 162,000 dollars. Adding the volumes of the effluents released by the main industries of the

district and the sewage treatment of LujPn city, we estimated that the river receives a total effluent discharge of 20,903 m3/day. The provincial law of conservation and protection of water bodies (Ley Provincial 5,965) establishes maximum concentrations of BOD and COD for industrial effluents, being respectively 50 mg/l and 250 mgl. Assuming that all the effluents released to the

river observed the standards proposed by the law, the oxygen necessary to cover the BOD is 1,395 todday, while the oxygen needed for COD compensation is 6,976 todday. The oxygen provided by the river flow and the oxygen needed to cover the expected biological and chemical demands produced by human activities were

estimated at three reaches of the mid-course (Table 1). According to the estimations presented in Table l, theoretically the river could cover the biological but not the chemical oxygen demand produced by human activities. We then asked whether these estimations represent what really happens in the river. To answer this question, data of dissolved oxygen

concentration, BOD and COD determined at the three sites of the mid-basin between 1997 and 1999 were used. The ratios BOD/dissolved oxygen and COD/dissolved oxygen were calculated, both indicating the number of days needed to cover the registered oxygen demand. A ratio equal to one implies that the oxygen demand is satisfied in only one day, while a value bigger than one

means that a remained demand exists, and it should be accumulated day by day (Figures l and 2).

The BODIoxygen and CODloxygen ratios were generally higher than one, indicating that the oxygen provided by the river flow cannot satisfy the oxygen demand produced by human activities. It can also be observed in Figures 1 and 2 that no clear differences were detected among sites. These results support the estimations of Table 1, indicating that the depuration capacity of the river was saturated, and that the self-purification process is impossible in the current situation.

Table I. Relation between the oxygen provided by the river flow and the expected oxygen demand produced by human activities at three sites of the mid-course of LujPn river (Sl: Olivera town; S2: JPuregui town;

S3: LujLn city).

Rivcr Oxygcn Expected Diffcrcncc Expected Diffcrcncc scction providcd oxygen (BOD) oxygen (COD) (dissolved demand (ton 02/day) demand (ton O,/day)

Ox~gcn) (BOD) (CoD) (ton 02/day) (ton 0,lday) (ton O,/day) S I 69 1.2 330.2 361 1651 -963

S2 1339.2 121.2 1218 606 733 S3 648 943.75 -395 47 18.75 -4070.75 Total 2678.4 1395.15 1184 6975.75 -4300.75

Figure 1. Days of river work needed to cover the biological oxygen demand (BOD) at three sites of the mid-course of the LujPn river (Sl: Olivera town, S2: Jauregui town; S3: Lujin city).

Figure 2. Days of river work needed to cover the chemical oxygen demand (COD) at three sites of the mid-course of the LujPn river (S I: Olivera town, S2: Jhuregui town; S3: Lujan city).

4 Discussion

Our results show that the river has the capacity to cover the BOD, provided that the industrial and sewage effluents be released according to the standards determined by the legislation. But the self-depuration work that the river would need to make in the real conditions is from 3 to 10 times higher than its real capability. Considering the chemical oxygen demand (COD), the river depuration capability is exceeded by more than 38 times. This indicates that the legal standards are not followed by the industries, or that the degradation of chemical substances consumes most of the dissolved oxygen, being it too scarce to reduce the biological degradable pollution. It must be noted that our analysis has only taken into account the chemical and biological water demand, but if we consider oxygen demand by the sediment, the differences between the oxygen provided by the river and the oxygen demand would be surely higher [13]. Economic estimations of the depuration costs can be obtained by multiplying the mean value of a day of river work by the number of days needed to complete depuration each month. The total sum reaches 150 billion dollars per year to consume the total BOD, and 400 billion dollars per year to consume the total COD, attaining the depuration of most part of the effluents released to the river. The recuperation costs are very high to be faced by a particular district government, but it may be possible to build alternatives scenarios for recovery of the river water quality [14]. It is very important to consider the river as a valuable resource; consequently, the restoration should not be prioritized only when economic conditions are favorable, because the rivers offer irreplaceable life-support services [15]. The method proposed in this study can be employed to

calculate the cost of remediation of a river. These costs could be then covered by distributing them proportionally among the industries and cities that release effluents to the river without an adequate treatment. Although it is no possible that the river crosses the same site several times to complete the task of self depuration?, it is possible to elongate it, as Margalef [l61 proposed. The way to elongate a river is to construct treatment stations, because they make in a short length, the work that the river would carry out in a longer one. These stations are present in industries of the mid-basin of the LujPn river, but it is indispensable that they attain an adequate performance to reduce

COD and BOD load to levels that could be then processed by the river.

Acknowledgments

This study could not be made without the help in the sampling process of Oscar Clarensio, Marta Banchero, Silvia Rivelli, Walter Cuevas y Eva Berezin (Direccibn de Bromatologia y Medio Ambiente, Municipalidad de Lujin).

Special thanks to Claudia Feijob and Charles Coviella for the revision of the English text.

References

[I] Kneese, A.V. & Schultze, Ch.L., Costo de fa contaminacicin. Editorial Marymar, 188 p. Buenos Aires. 1976.

Ecologia y Negocios. 8, [2] Conte Grand, M., El ambiente y el mercado. pp. 26- 28, 1998 [3] Brailovsky, A.E., lntroduccirin a1 estudio de 10s recursos naturales. EUDEBA, Buenos Aires, 273 pp., 1983. [4] Andrade, M.I., Factores de deterioro ambiental en la cuenca del Rio LujLn.

Contrihucicin del lnstituto de Geograjia, Fac. de FilosoJia y Letras (UBA),

224 pp., Buenos Aires, 1986. [5] Sala, J.M., Contribuci6n a1 conocimiento geohidrologico de la porcibn oriental de la cuenca del rio LujPn y las correspondientes a 10s arroyos Escobar, Garin, Claro y de Las Tunas. Consejo Federal de Inversiones, pp. 1-49, EASNE, Buenos Aires, 1972.

[6] Club de Ciencias. Saneamiento del rio Lujcin. Concejo Deliberante Ciudad de Lujin. LujPn. pp. 1-3 1, 1974 [7] Del Giorgio, P.A., Vinocur, A.L., Lombardo, R.L. & Tell, H.G., Progressive changes on the structure and dynamics of the phytoplankton community along a pollution gradient in a lowland river- a multivariate approach.

Hydrohiologia, 224, pp. 129-154, 1991. [8] Alberdi, J.L., SPenz, M.E., Di Marzio, W.D. & Tortorelli, M. del C., Estudio de la calidad de agua del rio LujQ. Parte 1. Resumenes I1 Congreso Latinoamericano de Ecologia, pp. 67-68, 1992.

[9] Ventura, A.S., Macro, T.A. & Momo, F.R., Contamination del rio LujPn (Buenos Aires, Argentina). Caracterizaci6n fisica y quimica de la calidad del agua. Resumenes 11 Congreso Argentino de Limnologia. 157 pp., 1997.

[lOJGiorgi, A., Banchero, M., Rivelli, S., Clarensio, 0. & Cuevas, W., Algunas variables indicativas de la calidad del agua del rio Lujin en su tramo medio. Actas Vfl Jornadas Pampeanas de Ciencias Naturales, pp. 155-162, 1999. [l l] Metcalf & Eddy. Tratamiento y depuracirin de las aguas residuales.

Editorial Labor, 836 pp., Barcelona, 1977 [12]GonzBlez, J.O. Sistemas de desagiies cloacales. Infirme de Pasantia Municipalidad de Lujdn, 99 pp., Li!jBn. 1999 [13]Shanhan, P., Henze, M., Koncsos, L., Rauch, W., Reichert, P,, Somylyody,

L. & Vanroileghem, P., River water quality modelling: 11. Problems of the art. Wat. Sci. Tech., 38(11), pp. 245-252, 1998. [l41 Kamal, M.M., Malmgren-Hansen, A. & Badruzzaman, A.B.M., Assessment of pollution of the River Buriganga, Bangladesh, using a water quality 40(2), model. Wat. Sci. Tech., pp. 129-136, 1999. [l51Everard, M., Aquatic Ecology, Economy and Society: The place of Aquatic Ecology in the Sustainable Agenda. Freshwater Forum 13, pp. 3 146,2000. [l61 Margalef, R., Limnologia. Omega. 10 10 pp., Barcelona, 1983.