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Pathogen removal in Upflow Anaerobic Sludge Blanket (UASB) Reactors.

Pathogen Removal in UASB reactors

Click here to download Manuscript: PaperRosaElena2010f.doc

Pathogen removal in Upflow Anaerobic Sludge Blanket (UASB)

Reactors

Rosa Elena Yaya Beas*, Grietje Zeeman*, Marc Dengremont*, and Jules B. van Lier**,

* Sub-Department of Environmental Technology, Wageningen University , Bomenweg 2, P.O. Box 8129, 6700EV

Wageningen, The Netherlands

Environmental Engineering Faculty, National University of Engineering,

(E-mail: rosa.yayabeas@wur.nl; grietje.zeeman@wur.nl;shiryu_marco@http://www.wendangku.net/doc/ddcd1dc358f5f61fb7366629.html)

** Section of Sanitary Engineering, Department of Water Management, Faculty of Civil Engineering, Delft

University of Technology, P.O Box 5048, 2600 GA Delft, The Netherlands

(E-mail: J.B.vanLier@tudelft.nl])

Abstract

Pathogen removal in UASB reactors is generally perceived as very poor. However, the removal of

nematode eggs in UASB systems is conflictingly documented, ranging from reasonable to

excellent. Research is conducted to elucidate the pathogen removal capacity of UASB reactors

with a focus on Helminth eggs. The removal capacity applying different hydraulic conditions was

estimated by using artificial latex beads, simulating Helminth eggs. Additionally, the Helminth

eggs removal is assessed in a UASB reactor treating domestic wastewater located in Lima (Peru).

The most common Helminth eggs found in the studied wastewater were Ascaris, Trichuris and

Strongyloides. The study demonstrated that with upflow velocities exceeding 1.5 m.h-1 a Helminth

egg removal efficiency exceeding 80% is feasible. Total and faecal coliforms removal varied from

0 to 82.60%. Results show that when pathogen removal is targeted, the UASB reactor must be

followed by an adequate post treatment system for treating the remainder of Helminth eggs and

faecal coliforms.

Keywords

Pathogens, UASB reactor, sludge, helminths ova, Faecal coliforms

1 INTRODUCTION

The presence of microbial pathogens in polluted, untreated and treated waters poses a considerable

health risk to the general public. Particularly when treated wastewaters are used for agricultural

purposes, the presence of pathogenic organisms may limit its application potential. Pathogenic

organisms in wastewater are very diverse and include bacteria, viruses, protozoan cyst and helminth

eggs (see Table 1). The pathogenic organisms can be classified in 4 groups: bacteria, protozoa,

viruses and Helminths .

Bacteria are microscopic organisms ranging from approximately 0.2 to 10 μm in length. One the

most common pathogenic bacteria found in municipal wastewater belongs to the genus Salmonella.

Other bacteria isolated from wastewater include Vibrio species (i.e. Vibrio cholerae),

Mycobacterium, Clostridium, Leptospira an Yersinia species. Coliform bacteria are commonly used

as indicators of faecal contamination and the presence of pathogenic species. While coliforms

generally respond similar to environmental conditions and treatment systems as many bacterial

pathogens, coliform bacteria determinations by themselves do not adequately predict the presence

of pathogenic viruses and protozoa (Asano, 1998).

Protozoa is a collective term for unicellular eukaryotes lacking cell walls. Previously considered as

a separate phylum, protozoans are often now classified along with algae and other simple

unicellular eukaryotes in the kingdom Protista. The pathogenic protozoa of most interest in water

and wastewater are Giardia intestinalis (formerly Giardia lamblia ) and Cryptosporidium parvum.