Study of the impact of Oum Azza landfill leachates on the environment of Rabat - Morocco
Abstract
The problem of solid household waste has arisen with great sharpness in recent decades. In particular, the management of leachates and the neutralization of their environmental impacts. The need for Morocco to meet the environmental challenge and put itself in logic of sustainable development has led to an awareness of this issue and the promulgation of the new law 28-00 on waste management and their elimination.
The objective of this research work is the characterization of the organic and mineral load of leachate from the Oum Azza landfill and the evaluation of its environmental impacts on the city of Rabat. For this a campaign of 24 samples was undertaken in 2011.
The physicochemical characterization of leachates has revealed that these liquid discharges are: • Very high inorganic matter with mean MES = 470mg / L; Average BOD5 = 5522 mg of O2 / Land COD = 12626 mg / L; • Very charged in mineral matter expressed in terms of electrical Conductivity (mean = 33969 μs / cm); • Have an average temperature of 24.5 ° C and a pH of 8; • A chloride concentration of 4289 mg / L; • Average sodium levels in the order of 3049 mg / L; • Average total nitrogen levels of 4090 mg / Land ammonia in the order of 3207 mg / L; • Average level of phosphates of the order of 35 mg / L; • Average sulphates levels of 35 mg / L.
The Rabat landfill represents areal nuisance for health and the environment because of the toxic characteristics of pollutants and bad odors. It is therefore essential to treat these liquid discharges and install a WWTP to mitigate the environmental impact of leachate.
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Introduction
In Morocco, like all the countries of the world, socio-economic activities coupled with population growth and changes in consumption patterns generate a large production of household solid waste [1]. In the face of demographic, industrial, urbanistic and tourist development, the problem of waste has arisen with great acuteness. The amount of household waste produced poses a serious threat to the environment as the current conditions for the collection, transport, disposal, recycling or destruction of such waste are inadequate [2].
The dump of Oum Azza is located a few kilometers east of the city of Rabat, on the right bank of the A5 motorway from Rabat to Casablanca and Kenitra. Initially it was a wild dump located near the urban perimeter of El Menzeh center and Ouled Mbarek Commune. The proximity to the main wind direction facilitates the spread of smoke, odors and plastic bags to nearby cities.
Like other Moroccan cities, Rabat faces an exponential increase in the amount of household waste produced by its inhabitants. Unfortunately the landfilling of waste and the accumulation of leachates in large storage ponds has contributed to the birth of a new environmental problem due to their pollutant loads and the nauseating odors that emerge [3]. The present work aims to characterize and evaluate the pollutant load of the Oum Azza de Rabat landfill by physicochemical analyzes of raw leachates collected in
Conclusion
The electrical conductivity reflects the total mineralization of water [9]. The average value recorded is 20115 μs / cm and is much higher than the Moroccan standards for the quality of water intended for irrigation (limit value <8700) and gives leachates a highly alkalizing power that is very dangerous for all cultivated plants [17].
The sodium has an average concentration of 3049.8 mg / L. This concentration of Na + ion is higher in leachate, and exceeds the Moroccan standard of water quality for irrigation. A large amount of sodium ions in the water affects the permeability of the soil and poses infiltration problems. This is due to the fact that the sodium present in the soil in exchangeable form replaces the calcium and magnesium adsorbed on the soil clays and causes the dispersion of the particles in the soil. This dispersion results in the alteration of soil aggregates. The soil then becomes hard and compact, reducing the infiltration rates of water and air, and consequently modifying the soil structure.
The sulphates ions (SO 2-) are sulphated compounds whose presence in water results from a contamination mainly related to 4 the discharge of domestic and industrial effluents or a phenomenon of natural reduction of sulphates. The average value in leachate is of the order of 35 mg / L. They are the source of bad odors emanating from leachates. The ammonium ion, NH4 +, is the reduced form of nitrogen. It comes mainly from the decomposition of natural proteins contained in phytoplankton and zooplankton. It can also be derived from the input of effluents from domestic, industrial or agricultural waste. The average value of the concentration of the NH4 + ion of the leachate of Oum Azza recorded during the study period is 3207 mg / L. According to the standard standard committee and Law 11-03, [14], ammonium does not meet discharge standards.
The chloride ions are anions of chlorine. This element is very abundant in the environment. It is present in water, soil, rocks, as well as in wastewater and leachate. The average chloride contents are 4289 mg / L. These results are consistent with those of previous studies [18-22].
In addition, the ammonium ion (NH +), by nitrification is transformed into nitrites (NO -) and nitrates (NO -) and oxidized 4 2 3 by the bacteria of the genus Nitrosomonas, then by the bacteria of the genus Nitrobacter [23]. Nitrates are very soluble in water; they migrate easily into the water table [24].
The average value of the BOD of the leachates studied is 5522 mg of O2 / Land it is well above the limit value of the 5 Moroccan standard of direct discharges which is 100 mg of O2 / L. Similarly, the COD value of 12626 mg / L exceeds the normand can be the basis of a strong fermentation.
Bad odors systematically accompany a project of storage of household waste. Odors are due to the presence of hydrogen sulphide in the landfill gas and the decomposition of organic matter.
Landfill gas is composed of methane, carbon dioxide, oxygen, nitrogen, carbon monoxide, hydrogen, and hydrogen sulphide. Only carbon monoxide and hydrogen sulphide are likely to be toxic to humans, beyond a threshold.
Unfortunately in the project of Oum Azza, smells and fumes of gas have areal impact given the proximity of homes not far from the site of Oum Azza. This is the example of the El Manzeh housing estate about 2 kmwest of the project site. However, a dominance of the west sector winds closely followed by wind from the north significantly reduces the impact of odors and different gaseous emissions to this new subdivision [25-26].
This situation is exacerbated by the non-control and control of industrial, special and hazardous waste generally sent to wild dumps without pre-treatment [27-28].
In conclusion, the concentrations found in the raw leachates of Oum Azza exceed the standards for wastewater quality recommended by WHO [29] and [14]. In addition, spatiotemporal monitoring of several other factors such as pathogens, trace elements and pesticides must provide us with the true level of pollution. Thus, the area of the landfill is affected by biological and chemical pollution that puts at risk the underlying water table.