Phosphorus removal and recovery from wastewater by highly efficient struvite crystallization in an improved fluidized bed reactor

Adsorptive Behavior of Prepared Metal-Organic Framework Composites on Phosphates in Aqueous Solutions

As an efficient water treatment method for treating dilute solution systems, electrosorption is promising for the separation and recovery of organic compounds, wastewater treatment, and deep purification of water. Here, two types of UiO-66 samples were prepared using the solvothermal synthesis method, and the effects of different regulators on the microstructure of materials were compared using the various characterization methods. The electrochemical properties of the activated carbon and two types of materials were tested by cyclic voltammetry and AC impedance spectroscopy, and the desalination effect of the materials on phosphate was investigated. The UiO-66 material with uniform-size particles, smaller-size particles, and more surface adsorption sites exhibited better phosphate removal and adsorption capacity. It was found that the desalination process of the UiO-66 material is reversible, and the adsorbent material can be reused, which is advantageous for engineering applications.

Ferrihydrite-impregnated granular activated carbon (FH@GAC) for efficient phosphorus removal from wastewater secondary effluent

Adsorptive removal of phosphorus from wastewater effluents has attracted attention because of its reduced sludge production and potential P recovery. In this study, we investigated granular activated carbons (GACs) impregnated with amorphous ferrihydrite (FH@GAC) for the sorption of phosphorus from aqueous solutions. Preoxidation of intact GAC surfaces using an oxidant (e.g., hypochlorite) and strong acids (e.g., HNO₃/H₂SO₄) was performed to create active functional groups (e.g., carboxyl or phenolic) for enhanced iron binding, leading to greater phosphorus uptake. Both the rate and the capacity of phosphorus sorption onto FH@GAC had significant, positive relationships (Pearson correlation coefficient r > 0.9) with the product of surface area and Fe content. The pseudo-second-order reaction kinetics explained the P sorption rate better than the pseudo-first-order reaction kinetics, whereas the Langmuir model fit the P sorption isotherm better than the Freundlich model. The iron content in the FH@GAC increased significantly (>10 mg/g) when GAC (e.g., BMC1050) was preoxidized by a 1:1 (w/w) concentrated HNO₃/H₂SO₄ mixture. The Langmuir maximum P sorption capacity of a functionalized FH@BMC1050 adsorbent prepared with acid pretreatment was estimated to be substantial (5.73 mg P/g GAC corresponding to 526 mg P/g Fe). This sorption capacity was superior to that of a FH slurry, possibly because the nano-sized FH formed inside the GAC pores (<2.5 nm) can bind phosphate ions more effectively than FH aggregates. Fixed-bed column reactor operation with bicarbonate regeneration showed potential for efficient, continuous phosphorus removal by FH@GAC media.

Potential Recovery Assessment of the Embodied Resources in Qatar’s Wastewater

Due to the ever-growing demand for natural resources, wastewater is being considered an alternative source of water and potentially other resources. Using Qatar as an example, this study assesses the resources embodied in wastewater and paves the way to combine wastewater treatment with advanced resource recovery (water, energy, nitrogen, phosphorous, added value products) which can turn wastewater management from a major cost into a source of profit. In this sense, wastewater is no longer seen as a problem in need of a solution, rather it is part of the solution to challenges that societies are facing today. Based on estimated quantities of generated urban wastewater and its average composition, mass flow analysis is implemented to explore the maximum availability of major wastewater constituents (solids, organic compounds, nutrients, chloride, alkalinity, sulfide). An assessment analysis reveals that, in Qatar, more than 290,000 metric tons total solids, 77,000 metric tons organic compounds, 6000 metric tons nitrogen, 81,000 metric tons chloride, 2800 metric tons sulfide, and 880 metric tons of phosphorus are embedded in about 176 million m3 of urban wastewater annually. One promising valorization strategy is the implementation of anaerobic digestion with biogas production, and the organic materials contained in Qatar’s wastewater corresponds to more than 27 million m3 of methane (equivalent to an energy content of more than 270 GWh) per year. The results further suggest that the recovery of nitrogen, phosphorus, and sulfide should be given priority.