Loofah Sponges as Bio-Carriers in a Pilot-Scale Integrated Fixed-Film Activated Sludge System for Municipal Wastewater Treatment

Huyen T.T Dang,Cuong V Dinh,Khai M Nguyen,Roberto M Narbaitz,Nga T.H Tran,Thuy T Pham

doi:10.3390/su12114758

Abstract

Fixed-film biofilm reactors are considered one of the most effective wastewater treatment processes, however, the cost of their plastic bio-carriers makes them less attractive for application in developing countries. This study evaluated loofah sponges, an eco-friendly renewable agricultural product, as bio-carriers in a pilot-scale integrated fixed-film activated sludge (IFAS) system for the treatment of municipal wastewater. Tests showed that pristine loofah sponges disintegrated within two weeks resulting in a decrease in the treatment efficiencies. Accordingly, loofah sponges were modified by coating them with CaCO3 and polymer. IFAS pilot tests using the modified loofah sponges achieved 83% organic removal and 71% total nitrogen removal and met Vietnam’s wastewater effluent discharge standards. The system achieved considerably high levels of nitrification and it was not limited by the loading rate or dissolved oxygen levels. Cell concentrations in the carriers were twenty to forty times higher than those within the aeration tank. Through 16S-rRNA sequencing, the major micro-organism types identified were Kluyvera cryocrescens, Exiguobacterium indicum, Bacillus tropicus, Aeromonas hydrophila, Enterobacter cloacae, and Pseudomonas turukhanskensis. This study demonstrated that although modified loofah sponges are effective renewable bio-carriers for municipal wastewater treatment, longer-term testing is recommended.

Highlights

One of the greatest challenges for developing countries is wastewater treatment
It can be seen that the sponges have a porous and fibrous structure, which can provide a favorable environment for the attached bacterial growth
The modified loofah sponge pieces are covered by a white layer

Summary

Introduction

One of the greatest challenges for developing countries is wastewater treatment. Low-cost wastewater treatment utilizing local materials can contribute to addressing this challenge, especially in developing countries. The conventional activated sludge process (CAS) has been the standard treatment method. New fixed-film processes, such as moving bed biofilm reactors (MBBR) and integrated fixed-film activated sludge (IFAS) systems, have been widely applied [2,3]. These processes have performed well in terms of organics and nitrogen removal in both municipal [4,5] and industrial wastewater treatment applications [6]. The key differences between MBBR and IFAS are the possible longer hydraulic retention time and recycle of sludge in the IFAS system [7]

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Methods

Results

Conclusion