Environmental & Socio-Economic Studies
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Environmental & Socio-economic Studies DOI: 10.2478/environ-2019-0007 Environ. Socio.-econ. Stud., 2019, 7, 2: 1-9 © 2019 Copyright by University of Silesia in Katowice ________________________________________________________________________________________________ Original article Human impact of septic tank effluent on groundwater quality in the rural area of Ain Soltane (Ain Defla), Algieria Abdelkader Bouderbala Department of Earth Sciences, University of Khemis Miliana, Road of Thniet El-Had. Ain Defla 44225, Algeria E–mail address: [email protected] ORCID iD: https://orcid.org/0000-0001-9049-5665 _______________________________________________________________________________________________________________________________________________ ABSTRACT The impact of individual septic tank effluent on groundwater quality was investigated in the rural area of the Ain Soltane municipality in Algeria. This area has an important number of individual septic tanks, and it is devoid of a drinking water supply and sewerage systems. The septic tank is a pre-treatment solution of sewage by bacteria living without oxygen (anaerobic). The alluvial aquifer in this area is covered by a layer of good permeability on the surface, which can pollute groundwater by vertical transport of pollutants through the soil, including microbial contamination. Groundwater samples were collected from 33 wells in the dry period of 2016. The monitoring of groundwater quality has shown a significant degree of organic and inorganic pollution in the majority of wells, with very high concentrations of sulphate and chloride exceeding 450 mg/l and 250 mg/l respectively. The analyzes also show the presence of bacterial germs in the groundwater of which the origin is faecal (faecal coliform densities are above 10 organisms per 100 ml, and the Total Streptococcus is more than 240 colonies per 100 ml). Monitoring confirms the contamination of these wells from septic tanks and that it was moving into groundwater, which makes it unfit for drinking due to the pathogenic germs. This poses a major problem for public health. This study has identified the effects of septic tank effluent on groundwater quality in this area. KEY WORDS: groundwater quality, septic tank effluent, pathogenic bacteria, Ain Soltane ARTICLE HISTORY: received 18 September 2018; received in revised form 28 March 2019; accepted 8 April 2019 ________________________________________________________________________________________________________________________________________________ 1. Introduction constitutes a major risk to human health and to the natural environment due to their toxic chemical Numerous diseases influencing the world's component and to pathogenic microorganism loads population are connected to the contamination of (HANCHAR, 1991). surface water or/and groundwater from untreated The microorganisms have the ability to migrate domestic and industrial wastewater. The nature through the soil matrix, that increase the probability of the cleared water has been increased since of groundwater contamination. Moreover, there industrial development, economic and population are numerous sicknesses caused by bacteria, such as development (REAY, 2004). According to the World diarrhea, dysentery, cholera, and typhoid fever. Health Organization (WHO, 2008), 75% of illnesses The use of septic tanks in rural areas as a system of the population on the planet are connected to of wastewater treatment contributes directly to water contamination (ODUKOYA & ABIMBOLA, 2010; the contamination of groundwater (REDDY & DUNN, AL-KHARABSHEH ET AL., 2013; ODUKOYA ET AL., 2013). 1984). These are the largest systems used in rural As a consequence the control and monitoring of areas in Algeria, thus, it is important to know and water quality, specifically wastewater, are becoming understand the impact of sewage effluent infiltration very necessary. Without treatment, this wastewater from septic tanks on the quality of groundwater, 1 especially in the alluvial unconfined aquifer. Septic by private drillings and by a pressure network tanks are built to treat human wastewater, and to supplied by dams. The groundwater of the Upper attenuate organic matter, and microorganisms. They Cheliff plain is used for drinking, irrigation, and are placed in the unsaturated zone, which can industrial purposes. purify water due to this zone. At an average flow The study area is located in a rural agglomeration of 0.15 m3/day, septic tanks are a significant source of the Ain Soltane province, which located in the of effluent recharge, with a large concentration of south of this province. We note that, the neighboring nitrogen and phosphorus, and they can in some cases cities of the plain have wastewater discharges attenuate nitrogen, but are ineffective at attenuating towards the stream of the wadi Cheliff river, due pathogens, organic matter and phosphorus (YATES, to the absence of a wastewater treatment plant, 1985; FUBARA-MANUEL & JUMBO, 2014; PANDEY ET whereas the rural agglomerations use individual AL., 2014). The transport of solute through soil septic tanks for the discharge of wastewater, which depends closely on the purifying power of the soil. represents one of the main environmental problems The different pollutants constitute permanent facing the plain, due to its impact on superficial dangers to both human and animal health and and groundwater resources (Fig. 1). even to the soil and plants (ROBERTSON & CHERRY, This rural agglomeration with about 10 000 1992; LUOSTARINEN & RINTALA, 2007). inhabitants spread over an area of about 3000 The aim of this work was to determine the hectares, has no network systems for drinking or concentrations of nitrate, chloride, and sulphate in for sewerage. The local inhabitants use private the groundwater samples in the alluvial unconfined wells for drinking supplies and septic tanks to aquifer of Upper Cheliff, to evaluate the effect of discharge wastewater. septic tank effluent on the groundwater quality and to check the role of the unsaturated zone as a natural system of wastewater purification. 2. Study area The Upper Cheliff plain is located approximately 120 km south west of the capital Algiers, between 36°10’ and 36°20’ north latitude and 02°00’ and 02°25’ east longitude and covers an area of 375 km². The plain is confined between the massif of Zaccar in the north and the Ouarsenis chain in the south. Fig. 1. Diagram of sewage percolation and transport from the The alluvial plain of Upper Cheliff is characterized septic tank to pumping well by a Mediterranean semi-arid climate, with hot dry summers and cold rainy winters. The annual 3. Geological framework average temperature for the period of 1980-2014 was 19°C, and the precipitation average for the The Upper Cheliff plain is elongated in an east- same period was about 400 mm. The estimation west direction within the Tellian Atlas (Fig. 2). of the real annual evapotranspiration by the The stratigraphical succession in the study area Thornthwaite method gives a value of 328 mm, from the older to recent formations is the following while runoff estimated by the Tixeront-Berkaloff (BOUDERBALA, 2017; BOUDERBALA & GHARBI, 2017): method gives a value of 40 mm, however, the - The Permiam-Triassic is observed in the Zaccar infiltration is about 32 mm. The hydrographic and Doui massifs and is formed by an alternation network of the study area is extremely dense. The of black schist, clays and quartzites; most significant Wadis are the main Cheliff Wadi - The Triassic is characterized by massive gypsum and its tributaries like Deurdeur, Harreza, Boutane, and dolomite formations; Erraihane, Telbanet and Massine. Three dams were - The Jurassic in the Zaccar massif is mainly built on the periphery of the Upper Cheliff plain: underlain by sedimentary rocks of limestone, Ghrib, Harreza and Derdeur. These dams and the dolomite and other carbonate rocks. Its thickness groundwater of the alluvial aquifer contribute to can reach 1000 m. While the Jurassic rocks in the irrigation of the agricultural plain with more the Doui massif are formed mainly of dolomitic than 20,000 ha irrigated. limestones; The larger part of the Upper Cheliff plain is - The Cretaceous outcrops on the lateral borders occupied by vegetables and tree crops and the other of the plain are represented by the following parts are used for cereals. The irrigation is ensured series: 2 . A series of Neocomian schists with a thickness - Old alluvial deposits are represented by of about 1000m; conglomerate and pebbles. Gray schist alternating with benches of - The calcareous crust is formed by calcareous tufa quartzite of Albian-Aptian, with a thickness whitish, compact or powdery. It is especially near to 1000 m; developed in the southern boundary of the . It is intercalated by yellowish limestone of Cheliff plain. the Senonian. - The cone of detritic deposits (alluvial cone) is - The Miocene formation is about 300 m in developed on the slopes of the boundary of the thickness. The Lower Miocene is essentially plain; it is formed of material washed down on formed by quartzites, sandstones and schists. the slopes of mountains by ephemeral streams. It is surmounted by Burdigalian (Middle Miocene) - The recent alluvial deposit is formed of pebbles, with sandstone, conglomerates and marls. The gravels, clay and silt which is covered by an Mio-Pliocene is formed of limestones, sandstones, organic soil. There are also alluvial deposits conglomerates, clays and the sandstones of observed