Recovery of phosphate from dewatered anaerobic sludge and wastewater by thermally treated P.oceanica residues and its potential application as a fertilizer

Treatment and recovery of phosphate from submerged anaerobic membrane bioreactor effluent using thermally treated biowaste and powder activated carbon

This study presents a novel treatment system using a submerged anaerobic membrane bioreactor (SAnMBR) followed by adsorption onto thermally treated biowaste, and ending with a final treatment using powdered activated carbon (PAC). Despite limited phosphate and ammonium ion removal during SAnMBR operation, thermally treated eggshell (EGSL) and seagrass (SG) received SAnMBR effluent and enhanced phosphate recovery, achieving removal rates of 71.8-99.9% and 60.5-78.0%, respectively. The SAnMBR achieved an 85% COD removal, which was slightly reduced further by biowaste treatment. However, significant further reductions in COD to 20.2 ± 5.2 mg/L for EGSL effluent and 57.0 ± 13.3 mg/L for SG effluent were achieved with PAC. Phytotoxicity tests showed the SAnMBR effluent after PAC treatment notably improved seed growth compared to untreated wastewater. In addition, volatile organic compounds (VOCs) were significantly reduced in the system, including common wastewater contaminants such as dimethyl disulfide, dimethyl trisulfide, phenol, p-cresol, nonanal, and decanal. Fractionation analysis of the solid fraction, post-adsorption from both synthetic and domestic wastewater, indicated that for SG, 77.3%-94% of the total phosphorus (TP) was inorganically bound, while for EGSL, it ranged from 94% to 95.3%. This study represents the first attempt at a proof-of-concept for simultaneous treatment of domestic wastewater and phosphorus recovery using this integrated system.

Heat and ZnCl2 chemical carbonization of date stone as an adsorbent: optimization of material fabrication parameters and adsorption studies

In the present study, the optimization of factors for the fabrication of highly adsorptive activated carbon from agricultural waste (date stone) was investigated by using ZnCl₂ as a chemical agent during the heat treatment. ZnCl₂ acts as a dehydration agent during the heat treatment, allowing a better porosity. In addition, it boosts the fragmentation of the lignocellulosic structure and the condensation of carbon rings. The findings of this investigation showed that the synthesis conditions for better ZnCl₂ chemical/heat carbonization to fabricate an adsorbent from date stone are 700 °C, 120 min, and 2.0 g/g. The characterization analysis showed that the as-prepared activated carbon exhibits a surface area of 1036 m²/g, an iodine number of 928.5 mg/g, and phenol number of 2.1 mmol/g, which are comparable to commercial activated carbons. Batch sorption tests to remove methylene blue (MB) from water showed a maximum adsorption capacity of 384.6 mg/g using the prepared activated carbon. Equilibrium data was best fitted by the Langmuir isotherm model. It was found also that the kinetic adsorption data obeyed the pseudo-first order, and both external diffusion and intra-particle diffusion control the adsorption. Based on the obtained results, the optimization of synthesis conditions may help the transfer of technology in terms of agriculture-based material valorization towards the environmental remediation.

Phosphorus recovery from wastewater and bio-based waste: an overview

Phosphorus is one of the most important macronutrients needed for the growth of plants. The fertilizer production market uses 80% of natural, non-renewable phosphorus resources in the form of phosphate rock. The depletion of those deposits forces a search for other alternatives, including biological waste. This review aims to indicate the most important ways to recover phosphorus from biowaste, with particular emphasis on wastewater, sewage sludge, manure, slaughter or food waste. A comparison of utilized methods and directions for future research based on the latest research is presented. Combining biological, chemical, and physical methods with thermal treatment appears to be the most effective way for the treatment of wastewater sludge in terms of phosphorus recovery. Hydrothermal, thermochemical, and adsorption on thermally treated adsorbents are characterized by a high phosphorus recovery rate (over 95%). For animal by-products and other biological waste, chemical methods seems to be the most optimal solution with a recovery rate over 96%. Due to its large volume and relatively low phosphorus content, wastewater is a resource that requires additional treatment to recover the highest possible amount of phosphorus. Pretreatment of wastewater with combined methods seems to be a possible way to improve phosphorus recovery. A compressive evaluation of combined methods is crucial for future research in this area.