Denitrification of water in packed beds using bacterial biomass immobilized on waste plastics as supports

Ecological Engineering 53 (2013) 329–334

Denitrification of water in packed beds using bacterial biomass immobilized on

waste plastics as supports

A. Cheikh

_{, A. Yala}

_{, N. Drouiche}

_{, N. Abdi}

_{, H. Lounici}

_{, N. Mameri}

a _{Laboratoire BIOGEP, Ecole Nationale Polytechnique, B.P. 182-16200, El Harrach, Algiers, Algeria}

b _{Centre de Recherche en Technologie des Semi-Conducteurs pour l’Energétique (CRTSE), 2, Bd Frantz Fanon BP140, Alger – 7 Merveilles, 16027, Algeria} c _{University of Technology of Compiègne, Chemical Engineering Department B.P. 20.509, 60205 Compiègne Cedex, France}

a r t i c l e i n f o

a b s t r a c t

Article history:

Received 10 August 2012

Received in revised form 1 December 2012 Accepted 3 December 2012

Available online 27 December 2012 Keywords: Denitrification Nitrate Nitrite Biofilm Immobilized biomass Plastic wastes supports

The present work investigates a novel water denitrification technique based on immobilized bacterial biomass using various plastic wastes as supports PVC (polyvinyl chloride), HDPE (high density poly - ethylene) and LDPE (low density polyethylene) in packed columns. The efficiency of these supports is compared with a conventional support, granular activated carbon (GAC). The results obtained for denitri- fication under various operating conditions showed that working at a high fluid velocity does not affect the bacterial behavior adversely. The denitrifying bacteria were able to treat water at an inlet nitrate concentration of 600 mg L−1 _{with removal efficiency near to 100%. The column packed with porous GAC}

as a support quickly became plugged in contrast to the nonporous LDPE which possesses a rough surface for film support and delivers almost the same performance as GAC. It was found that sulfate ions promote denitrification, but chloride inhibits it. The effectiveness of the packed-bed process is not diminished significantly by the coexistence of both types of ion in the feed stream.

© 2012 Elsevier B.V. All rights reserved.

1. Introduction

Over recent decades, a continuous increase of nitrate concen- trations (NO3−) in groundwater reserves and surface water has been observed. Nitrate pollution is a widespread problem in many countries, which can cause health hazards to both humans and ani- mals (Khalil and Richards, 2011; Jahangir et al., 2012; Morari et al., 2012). This pollution originates mainly from industrial activity and from intensive agricultural application of nitrogenous fer- tilizers and uncontrolled land discharge of wastewater Indeed, about 30–70% of nitrogen fertilizers used in agriculture is lost to the environment and found in nitrate form in surface waters and groundwater used for drinking water (Yapo et al., 2009; Adav et al.,

2010; Nancharaiah and Venugopalan, 2011; Köster et al., 2011).

At high concentrations, nitrate consumption causes methe- moglobinemia in infants (blue baby). Ammonia (NH3) may be oxidized to nitrate (NO3−) by bacteria such as nitrosamines and can be subsequently reduced to nitrites (NO2−) by other bacteria such as nitrobacter. The nitrites are more dangerous than the nitrates. The ingestion of nitrites can cause cancers in stomach or intestine

∗ Corresponding author at: Centre de Recherche en Technologie des Semi- Conducteurs pour l’Energétique (CRTSE), Department of Environmental Engineer- ing, 2, Bd Frantz Fanon BP140, Alger – 7 Mervielles, Alger 16000, Algeria. Tel.: +213 21 279880x192; fax: +213 21 279555.

E-mail address: nadjibdrouiche@yahoo.fr (N. Drouiche).

through nitrosamines, which are known carcinogenic compounds

(Ratel, 2000).

The use of immobilized microorganisms for denitrification has led to a wide range of practical biological processes (Moreno-

Castilla et al., 2003). Such operations present several advantages

compared to processes involving suspended biomass, such as reducing bioreactor size and allowing increased flow rates. Vari- ous materials have been used as supports to fix microorganisms (e.g., sand, gravel, coal, plastic, etc.), which are characterized by their high adsorption capacity and their irregular shape that acts as a shelter for bacteria (Wojnowska-Baryła and Zielin´ ska, 2002).

This work focuses on nitrate removal from an electrodialy- sis concentrate by biological denitrification using a biomass fixed grown on several plastic supports.

The comparison of performance of these plastic supports to that of granular activated carbon one was carried out. Nitrate and nitrite removal, in fixed bed reactors, was measured at several feed concentrations and flow velocities. In addition, the influence of chloride and sulfate ions on the denitrification kinetics was also studied.

2. Materials and methods

2.1. Microorganisms and culture medium

The microorganisms used in this study were obtained from an activated sludge present in a local municipal treatment plant. 0925-8574/$ – see front matter © 2012 Elsevier B.V. All rights reserved.

http://dx.doi.org/10.1016/j.ecoleng.2012.12.070

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Ecological Engineering