A bioflocculant-supported dissolved air flotation system for the removal of suspended solids, lipids and protein matter from poultry slaughterhouse wastewater C. Dlangamandla, S. K. O. Ntwampe and M. Basitere ABSTRACT In this study, two previously identified isolates, i.e. Comamonas aquatica (BF-3) and Bacillus sp. BF-2, were determined to be suitable candidates to utilise in a bioflocculant-supported dissolved air flotation (Bio-DAF) system as a pretreatment system for poultry slaughterhouse wastewater (PSW). A 2% (v/v) (bioflocculant:PSW) strategy was used for the DAF to reduce total suspended solids (TSS), lipids and proteins in the PSW, by supplementing the bioflocculants produced and the co-culture (C. aquatica BF-3 and Bacillus sp. BF-2) directly into the DAF. The Bio-DAF was able to reduce 91% TSS, 79% proteins and 93% lipids when the DAF system was operating at steady state, in comparison with a chemical DAF operated using 2% (v/v) alum that was able to only reduce 84% TSS, 71% proteins and 92% lipids. It was concluded that the Bio-DAF system worked efficiently for the removal of suspended solids, lipids and proteins, achieving better results than when alum was used. C. Dlangamandla S. K. O. Ntwampe (corresponding author) M. Basitere Bioresource Engineering Research Group (BioERG), Department of Biotechnology, Cape Peninsula University of Technology, P.O. Box 652, Cape Town 8000, South Africa E-mail: ntwampeS@cput.ac.za Key words | Bacillus sp., bioflocculant, Comamonas aquatica, dissolved air flotation, poultry slaughterhouse wastewater INTRODUCTION Dissolved air flotation (DAF) is a wastewater treatment tech- nique employed in the separation of low-density solids from wastewater (Al-Shamrani et al. ). This technique is highly dependent on the suitability of the sparging system used in the DAF. If sufficient pressure is applied to the diffu- sers, microscopic bubbles are formed when the wastewater is pumped into the flotation cell. The micro-bubbles gener- ated in the system can be harnessed for the removal of fats, oil and grease (FOG), suspended solids and biomass (Amaral Filho et al. ). The good effectiveness of this system can be attained when the size of the bubble is suit- able when compared with the size of the particles that have to be separated; furthermore, compatibility of the sur- face charges for both the suspended particles and the micro-bubbles can also influence the DAF’s operational effi- ciency (Han et al. ). The quantity of the micro-bubbles generated, including their size, is dependent on the pressure applied to the air diffusers. The addition of flocculants into the DAF can also enhance the efficiency of the system. In most cases, flocculation– flotation methods involve the addition of chemical flocculants into the system. Chemical flocculants such as aluminium sulfate and ferric chloride, as well as polyacrylamide, have been determined to be highly efficient. However, they are expensive, non-biodegradable, and can have a harmful effect on the environment; moreover, they have been deter- mined to be toxic to humans (Wang et al. ). These considerations prompted researchers to assess alternative solutions with minimal impact on the environment. Hence, bioflocculants have received much attention lately. These polymers are biodegradable, environmentally friendly and they do not pose a risk to human health. This part of the study mainly focuses on the application of bioflocculants produced by isolates from the poultry slaughterhouse waste- water (PSW), for their use in DAFs for the removal of suspended solids, FOG and protein matter from the PSW. The aim of the study was to design a bench-scale biofloccu- lant-supported DAF (Bio-DAF) and assess its efficiency in removing total suspended solids (TSS), protein and FOG from PSW; and to compare the efficiency of the Bio-DAF to those processes in which chemical flocculants are used, including a conventional DAF (control). 452 © IWA Publishing 2018 Water Science & Technology | 78.2 | 2018 doi: 10.2166/wst.2018.324 Downloaded from https://iwaponline.com/wst/article-pdf/78/2/452/475239/wst078020452.pdf by UNIVERSITE PIERRE ET MARIE CURIE user on 24 August 2018