Toxic compounds biodegradation and toxicity of high strength wastewater treated under elevated nitrogen concentration in the activated sludge and membrane bioreactor systems.
This research has assessed the removal efficiencies of toxic compounds in the high strength wastewater (the leachate and agriculture wastewater mixture) using the activated sludge (AS) and membrane bioreactor (MBR) technologies under two carbon to nitrogen (C/N) ratios (C/N 14 and 6) and two toxic compounds concentrations (8-396μg/L and 1000μg/L). In addition, the toxicity evaluations of the AS and MBR effluents to the aquatic environment were undertaken at five effluent dilution ratios (10, 20, 30, 50 and 70% v/v). The findings indicate that the AS treatment performance could be enhanced by the elevation of the nitrogen concentration. Specifically, the C/N 6 environment helps promote the bacterial growth, particularly heterotrophic nitrifying bacteria (HNB) and nitrifying bacteria (NB), which produce the enzymes crucial to the toxic compounds degradation. The improved biodegradation makes the effluents less toxic to the aquatic environment, as evidenced by the lower mortality rates of both experimental fish species raised in the nitrogen-elevated diluted AS effluents. On the other hand, the elevated nitrogen concentration minimally enhances the MBR treatment performance, given the fact that the MBR technology is in itself a biological treatment scheme with very high compounds removal capability. Despite its lower toxic compounds removal efficiency, the AS technology is simple, inexpensive and operationally-friendly, rendering the system more applicable to the treatment operation constrained by the financial, manpower and technological considerations.
Division of Biology, Faculty of Science and Technology, Rajamangala University of Technology Thanyaburi (RMUTT), Klong 6, Pathum Thani 12110, Thailand. Electronic address: jarungwit_b@rmutt.ac.th.
Jarungwit
J
Boonnorat
Excellent Center of Waste Utilization and Management (ECoWaste), King Mongkut's University of Technology Thonburi (KMUTT), Bangkhuntien, Bangkok 10150, Thailand.
Nimaradee
N
Boonapatcharoen
Department of Civil and Environmental Engineering, Faculty of Engineering, Srinakharinwirot University, Ongkharak, Nakhon Nayok 26120, Thailand.
Pradthana
P
Prachanurak
Research Center for Sustainable Energy and Technology (RSET), Institute of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
Ryo
R
Honda
Department of Environmental Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900, Thailand.
Supaporn
S
Phanwilai
D000818:Animals; D019149:Bioreactors / Q000382:microbiology*; D002244:Carbon / Q000737:chemistry; D005399:Fishes; D008567:Membranes, Artificial; D009584:Nitrogen / Q000737:chemistry*; D012722:Sewage / Q000382:microbiology*; D018675:Toxicity Tests; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000633:toxicity*
D002244:Carbon; D008567:Membranes, Artificial; D009584:Nitrogen; D012722:Sewage; D062065:Wastewater
Activated sludge (AS); C/N ratio; Membrane bioreactor (MBR); Toxic compounds; Wastewater treatment