Elimination of ammoniacal nitrogen existing in wastewater by infiltration percolation process

Ez-zahery

486

Elimination of ammoniacal nitrogen existing in wastewater by infiltration percolation process

M. Ez-zahery^*, S. Et-Taleb, R. Aba aaki, R. El haouti, M. Abbaz, S. Lhanafi and N. El alem

Environment and Materials Laboratory (EML), Ibn Zohr University, Faculty of Sciences, Department of Chemistry, PO Box 8106 ADAKHLA city, Agadir, Morocco

*Corresponding author. E-mail : [email protected]

Received 13 Sept 2014, Revised 01 Oct 2014, Accepted 24 Oct 2014

Abstract

Cluster development and human activity, be it domestic, industrial or agricultural, is responsible for the production of natural pollution (organic, inorganic,..). The objective of this research is to follow the evolution of ammoniacal nitrogen, nitrites and nitrates in domestic wastewater treated by the process of infiltration-percolation using sand of M'zar (region of Agadir, Morocco) as a filter material. The latter is characterized by the effective diameter (D₁₀) and the coefficient of uniformity (C_u) which is 0.15 and 1.46 respectively. The operating principle is based on an aerobic biological filtration on granular medium (sand).

The nitrogen content of treated water varies with the origin of raw sewage and sewage system conditions, the results we found show a 95% removal of this pollutant.

Keywords: Wastewater, Infiltration-percolation, gravel pack, Ammoniacal nitrogen

1.

Introduction

Urine is the main indicator of the presence of nitrogen in urban waste water and detergent is ammonium, ammonification reactions may occur that transform organic nitrogen to ammonium NH4 +

(reduced form of nitrogen), in fact the demand for oxygen by ammonia is very high they are molecules (nitrogen compound) odor causing [1]. These effluents which lack of management are a source of environmental pollution and pollution of surface and groundwater resources [2]. This aquatic pollution is an environmental problem which has serious consequences on the quantity and the quality of diverse maritime species. This is why the treatment of nitrogen in wastewater is very important before discharging it into the receiving surrounding.

Infiltration percolation is a low technology process used to treat primary and secondary effluents. It consists in the intermittent application of sewage on buried sand filters or permeable native soils [3, 4, 5]. Several physical, chemical and biological processes have hand in the purification system. The quality of water treated by this process on both the characteristics of the sand used (particle size, composition....) and the different sorts of pollutants existing in the raw wastewater and the climatic conditions [6].

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2. Materials and methods

This study aims to assess the treatment capacity of sand of M'zar (region of Agadir, Morocco) on domestic wastewater. The various analyzes carried out focus on the characteristics of the sand on the one hand and on the purification performance of the different nitrogenous parameters (NH₄⁺, NO₃^- and NO₂^-) of the urban discharges of Drarga (region of Agadir, Morocco) on the other hand during a one year follow period.

Purification is assured by the passage of waste water, after decantation, through the gravel pack. The assembly pilot fitted out at the Faculty of Sciences in Agadir consists of a PVC column of 19 cm in internal diameter and 2m in height filled with the same sand used in the wastewater purification station (Agadir, Morocco) Figure 1.

3. Results and Discussion

3.1 Granulometric analysis and mineralogic of sand 3.1.1 Granulometric Analysis

The main granulometric characteristics of a filter material are the effective diameter (D₁₀) (diameter of the sieve which passes 10% of particles), (D60) (diameter of the sieve which passes 60% of particles) and the coefficient of uniformity D₆₀ / D₁₀, the permeability, K = 100*(D₁₀)².

Figure 2. Grading curve of the sand

0 10 20 30 40 50 60 70 80 90 100

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

sand sieve(%)

D (mm) Sand of M'zar

Seen in face Seen in profile

Gravel Flacon of recovery Drain

Figure1. Experimental device

Sand of M’zar

Ez-zahery

488 Granulometric analysis is performed by sieving (grain distribution by size class on a series of square mesh sieve [7]. The values we found are: D₁₀ = 0.150 mm, D₆₀ = 0.220 mm, C_u = 1.46 and K = 0.023 (Figure 2)

3.1.2 X-ray diffraction

The study of X-ray has shown that the different components of this material are: silica SiO2, CaCO3 calcite (rhombohedral variety), the aragonite CaCO₃ (orthorhombic variety holoedre) and low albite Na(AlSi₃O₈) ₃. Which shows that this material is rich in silica and carbonates, so it's an alumina-silicate sand.

3.2 Analysis of wastewater

In this present work, we have studied the evolution of different nitrogenous forms (NH₄⁺, NO₃^- and NO₂^-) before (DW) and after (PW) treatment. The ammoniacal nitrogen content in the treated water varies according to the origin of the raw wastewater and of the conditions of the purification system, the net retention measured on ammoniacal nitrogen support the hypothesis of the rapid implementation of nitrification (Figure 3) [8]. The nitrogen, mainly as ammonia, is rapidly converted to nitrite and nitrate after oxidation in the presence of bacteria [9]. This explains that the nitration being faster than the formation of nitrites or that these latter are less stable and they disappear rather quickly in the natural medium (disproportionation) Figures 4 and 5. Thus, the treated wastewater is rich in nitrates; thereby, its reuse in agriculture can contribute to the preservation of water resources [10].

75 80 85 90 95 100

% Retention NH4+

Date of levy Figure 3. Studying evolution of NH4+

allowances for this process

0 100 200 300 400 500 600 700 800 900 1000

NO3-(mg/l)

Date de prélèvement DW PW

Figure 4. Studying evolution of nitrate of decanted (DW) and purified (PW) wastewater

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489 0

20 40 60 80 100 120 140 160

14/06/2005 14/07/2005 14/08/2005 14/09/2005 14/10/2005 14/11/2005 14/12/2005 14/01/2006 14/02/2006 14/03/2006 14/04/2006 14/05/2006 14/06/2006 14/07/2006

NO2-(mg/l)

Date de prélèvement DW PW

Figure 5. Studying evolution of nitrite of decanted (DW) and purified (PW) wastewater

4. Conclusion

The infiltration percolation process is most commonly used for sewage treatment, it serves the dual purpose of treating primary or secondary wastewater and recharging groundwater, with a view to reusing water, for the region has water deficit. The results of monitoring of treatment performance at the entrance (DW) and exit (PW) show that the sand used as a gravel pack is an efficacious material for the retention of the ammoniacal nitrogen, the latter oxidizes to NO2-

then to NO3-

which is the most stable form of nitrogen.

Therefore, the reuse of treated wastewater, by this process, in the field of agriculture is important because it is rich in fertilizing element (NO3-

).

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Et-taleb, R. Elhaouti, M. Abbaz , S. Lhanafi, M. Ez-zahery, R. Aba-aaki and N. El Alem. J. Mater. Environ.

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