Effects of salt concentration on floc characteristics and pollutants removal efficiencies in treatment of seafood wastewater by SBR

Abstract

Most seafood wastewater has been treated by the activated sludge process. Due to changes in salt concentration, pollutant loadings and raw materials, the process is not operated satisfactorily to meet effluent regulation. Most problems faced at present are solid liquid separation. In this study, effects of salt concentration on floc characteristics and pollutants removal efficiencies were investigated in treatment of seafood wastewater by SBR. For analyzing fractal dimension of flocs, the small angle laser light scattering (SALLS) method was applied using a Diffraction Particle Sizer (Malvern Instruments). Organic removal efficiencies (in terms of COD(Mn)) decreased with increasing salt concentration, but eventually reached a steady state. Fractal dimension and floc size also showed similar trends with changing salt concentration. The main reasons to reduced pollutant removal efficiencies were deteriorated biological activity and settling properties. The biological activity was affected faster than the floc characteristics by increasing salt concentration. The deteriorated settling properties were explained by decreased size and fractal dimension of floc due to increasing salt concentration. The settling properties of floc such as sludge volume index (SVI) and zone settling velocity (ZSV) were related to size and fractal dimension of floc. The fractal dimension of floc was better related to the settling properties than the size of floc.

Monitoring the stability of an Anammox reactor under high salinity conditions

“…Dahl et al [20], treating in a nitrifying system wastewater with high salinity (20 g Cl − L −1 ) and ammonia concentration of 120 mg NH 4 + -N L −1 , obtained a sludge with a SVI of 32 mL g VSS −1 . In other cases a negative effect was observed like in the case of Moon et al [21]. These authors found floc size decreased and settling properties deteriorated with increasing salt concentration when they treated seafood wastewater with a SBR at NaCl concentrations up to 10 g L −1 .…”

Image analysis application for the study of activated sludge floc size during the treatment of synthetic and real fishery wastewaters

“…Furthermore, filamentous bacteria, which are very important for the aggregates' structure, are also known to be highly sensitive to NaCl presence. It was already verified by several authors that with NaCl addition, the osmotic stress on microbial cells decreases the flocculation abilities (Moon et al 2002;Campos et al 2002). Hence, certain species of microorganisms may have been reduced, due to osmotic stress, leading to the release of their cellular components and thus increasing turbidity levels.…”

“…The existence of salt in wastewater reduces the populations of protozoa, resulting in higher dispersed bacteria contents, as most protozoa graze on bacteria, and lower sludge settling ability due to the fact that protozoa, on the course of their motion, break up the larger flocs. When the salinity of an effluent increases, the reduction of filamentous bacteria occurs (da Motta et al 2001), decreasing also the mechanical integrity and structure of the aggregates (Moon et al 2002). In the present work, the biomass structure response to a salinity increase was investigated based on the SVI and turbidity measurements.…”

Aerobic digestion of tannery wastewater in a sequential batch reactor by salt-tolerant bacterial strains

“…Some studies have been conducted on the degradation of complex wastewater using halophiles in SBR Irvine 1994, 1995;Kubo et al 2001;Moon et al 2002;Uygur and Kargi 2004;Lefebvre et al 2004). In this study, the salt-tolerant microorganism used by Senthilkumar et al (2008) for the treatment of tannery wastewater was used in a SBR.…”