Yunfei Yang,Xiang Cheng,Eldon R. Rene,Bin Qiu,Qian Hu
The iron materials are commonly employed to enhance resource recovery from waste activated sludge through anaerobic digestion (AD). The influence of different iron sources, such as Fe 2 O 3 , Fe 3 O 4 , and FeCl 3 on methane production and phosphorus transformation in AD systems with thermal hydrolyzed sludge as the substrate was assessed in this study. The results indicated that iron oxides effectively promote methane yield and methane production rate in AD systems, resulting in a maximum increase in methane production by 1.6 times. Soluble FeCl 3 facilitated the removal of 92.3% of phosphorus from the supernatant through the formation of recoverable precipitates in the sludge. The introduction of iron led to an increase in the abundance of bacteria responsible for hydrolysis and hydrogenotrophic methanogenesis. However, the enrichment of microbial communities varied depending on the specific irons used. This study provides support for AD systems that recover phosphorus and produce methane efficiently from waste sludge.
Phosphonate used as scale inhibitor is a non-negligible eutrophic contaminant in corresponding polluted waters. Besides, its conversion to orthophosphate (ortho-P) is a precondition for realizing bioavailable phosphorus recovery. Due to the feeble degradation efficiency with less than 30 % from classical Fenton commonly used in industrial wastewater treatment and itself vulnerable to strong inhibition interference of matrix chloride ions, we proposed an electrochemical approach to transform the native salt in the solution into oxidizing substances, sort of achieving beneficial utilization of matrix waste, and enhanced the ortho-P conversion rate of 1-Hydroxyethane-1,1-diphosphonic acid (HEDP) to 89.2 % (± 3.6 %). In electrochlorination system, it was found that HEDP rapidly complexed with Fe(II) and then coordinated in-situ Fe(III) to release free HEDP via intramolecular metal-ligand electron transfer reaction. The subsequent degradation mainly rooted in the oxidation of pivotal reactive species HClO, Fe IV O 2+ and 1 O 2 , causing C-P and C C bonds to fracture in sequence. Eventually the organically bound phosphorus of HEDP was recovered as ortho-P. This study acquainted the audiences with the rare mechanism of chloridion-triggered HEDP degradation under electrochemical way, as well as offered a feasible technology for synchronous transformation of organically bound phosphorus to ortho-P and elimination from phosphonates.
Zi-Bin Xu,Wen-Long Wang,Nan Huang,Qian-Yuan Wu,Min-Yong Lee,Hong-Ying Hu
2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) is an antiscalant that is widely used in reverse osmosis (RO) systems. Because of its high concentration in RO concentrate, eutrophication risk and anti-precipitation properties may affect subsequent treatments, therefore treatment strategies are needed to eliminate such substances. In this study, PBTCA was degraded by ozonation . The results show that PBTCA reacted with ozone molecules and hydroxyl radicals , with second-order rate constants of (0.12 ± 0.002) and (7.83 ± 1.51) × 10 8 L mol −1 s −1 , respectively. The phosphorus in PBTCA (P P ) was transformed into organic phosphorus except for PBTCA (P O ), and inorganic phosphorus (P I ); P O was further transformed into P I . The changes in the concentrations of these phosphorus forms were investigated by model simulation. Simulation showed that the rate of P P transformation into P O was 5.5 times higher than that into P I . PBTCA was ozonated much faster at alkaline pH than at acidic pH. This is ascribed to different amounts of ozone molecules and hydroxyl radicals, and their different reaction rates with PBTCA. Furthermore, anti-precipitation property was reduced during ozonation , as shown by the amounts and morphology changes of the precipitates. PBTCA concentration for 50% anti-precipitation (AP 50 ) did not change during ozonation, indicating that the transformation products generated during ozonation did not have anti-precipitation effects. Phosphorus in PBTCA was removed by ozonation–coagulation treatment. Total phosphorus and inorganic phosphorus were removed efficiently by using ferric chloride as a coagulant. The coagulants tended to bind with inorganic phosphorus to form flocs. Meanwhile, flocs were more easily to aggregate and precipitate as anti-precipitation effect was gradually removed, thus more phosphorus was removed. A combination of ozonation and coagulation removed PBTCA effectively and simultaneously reduced its anti-precipitation property and phosphorus.
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