Preparation of a novel organic-inorganic composite sludge bioflocculant (SBF) from dewatered sludge as raw material: Characteristics, flocculation mechanism and application for domestic sewage.

• The prepared SBF are composite polymers, including iron, aluminium and EPS. • The main factor affecting SBF preparation and flocculation reaction were is PH. • Flocculation mechanism is mainly chemical reaction and surface adsorption. • SBF is highly efficient in removing TP from domestic wastewater. • SBF enables production and utilisation cycles in wastewater treatment plants. In this work, a green sludge bioflocculant (SBF) was prepared via chemical hydrolysis of dewatered sludge and applied to flocculation of domestic wastewater. The process parameters for the preparation of the SBF were 1.80 % hydrochloric acid concentration, 60 min extraction time, and 4000 r/min centrifugation speed. SBF is polymeric flocculant composed of organic and inorganic compounds. Flocculation efficiency reached 97.31 ± 0.26 % under optimal flocculation conditions. Charge neutralization promotes the surface adsorption, bridging and net trapping and sweeping of Fe (OH) 3 , Al (OH) 3 and active functional groups O–H/N–H and C = O in SBF, which together achieve efficient flocculation reactions. SBF had high efficiency and stable flocculation performance for phosphorus in urban domestic wastewater, and the concentration of TP in effluent was lower than 0.30 mg/L. Therefore, SBF prepared from dewatered sludge has efficient flocculation properties and is suitable for removing pollutant phosphorus, which has good application prospects in the field of wastewater treatment. [ABSTRACT FROM AUTHOR]