Protein recovery from excess sludge for its use as animal feed

Application of ultra-sonication, acid precipitation and membrane filtration for co-recovery of protein and humic acid from sewage sludge

“…Since proteins and humic acid in sewage sludge always exist in the stable polymerized structure, ultra-sonication, alkaline pretreatment, and heating have been widely applied for enhancing their disintegration [15,16]. Meanwhile the dissolved proteins and humic acid can be recovered via proper technical methods [5,17].…”

“…Thus, the stabilization, harmlessness and resource utilization of sewage sludge have attracted more and more researchers' interest all over the world. Traditionally, anaerobic digestion, aerobic composting, combustion and landfill are employed to dispose the sewage sludge [5]. Considering sludge management costs, which can be as high as 50% of the total costs of WWTP, and the increasingly stringent environmental regulations on landfill [6], how to develop sustainable and new technologies for the efficient disposal and reuse of excess sludge is urgent [7].…”

Value-Added Products Derived from Waste Activated Sludge: A Biorefinery Perspective

“…More importantly, all methods reported in these studies lowered the heavy metal content of the original WAS considerably through alkaline precipitation. With the ultrasonic-alkaline method, Hwang et al even achieved non-detectable levels of other contaminants of concern such as aflatoxin B1, ochratoxin A and Salmonella D group organisms [17]. Ras et al investigated the efficiency of mechanical (i.e., ultraturax or sonication) and chemical (i.e., cationic exchange resin and triton) treatments on protein extraction from two activated sludges, as well as their compatibility with usual quantification methods [19].…”

“…Hydrochloric acid, sodium lignosulphate, sulphuric acid, acetic acid and ammonium sulphate were tested as precipitants, among which ammonium sulphate (40%) was observed to be most effective, providing maximum protein recovery (around 91%). Hwang et al later applied a hybrid process of ultrasonic-alkaline pretreatment followed by precipitation and drying to release and subsequently recover the intracellular protein from WAS [17]. The supernatant protein concentration was observed to be 3178 mg/L after pretreatment of WAS (5330 mg/L TSS) after treating the substrate with ultrasound (1.65 × 10 10 kJ/kg VSS) at pH 12 for 2 h. Zhang et al reported a method of enzyme (i.e., papain)-assisted hydrolysis to extract protein from WAS in the Shanghai Qingpu sewage treatment plant, China [18].…”

“…Protein recovery from secondary WAS from a paper mill can also be used as an eco-friendly source of wood adhesive. For example, Pervaiz and Sain used an alkaline cell-disruptive techniquesimilar to that of Hwang et al (2008)-to extract protein, with the end product achieving up to 41% the shear strength of traditional protein-based wood adhesive such as soy protein isolate and phenol formaldehyde resin [28].…”