RESUMEN
In this study, phosphate-rich supernatant at the end of anaerobic phase was extracted by a certain side-stream ratio for chemical precipitation to investigate the optimal conditions for phosphorus recovery. The effect of side-stream reaction on the performance of the mainstream enhanced biological phosphorus removal (EBPR) system was also explored. The experiment was carried out in a sequencing batch reactor (SBR) operated in an alternating anaerobic/aerobic mode with dissolved oxygen controlled at 1.0 mg · L-1. The results showed that the optimum magnesium source,temperature, stirring speed and reaction equilibrium time for side-stream phosphorus recovery were: MgCl2 · 6H2O, 25 °C, 150 rpm and 20 min, respectively. It was also observed that the average phosphorus removal efficiency of the mainstream system maintained as high as 90.7% during the side-stream extraction period despite insufficient time for phosphate uptake under limited dissolved oxygen condition and phosphate deprivation of polyphosphate-accumulating organisms (PAOs). Besides, the sludge settling performance of the mainstream EBPR system decreased with no sludge loss. Afterwards, phosphorus removal and sludge settling performance were restored with dismissing side-stream phosphorus recovery. This study suggested that side-stream extraction of anaerobic supernatant from a mainstream EBPR subjected to low dissolved oxygen conditions for chemical phosphorus recovery was feasible and environmentally friendly.
Asunto(s)
Fósforo , Ríos , Anaerobiosis , Reactores Biológicos , Aguas del AlcantarilladoRESUMEN
A significant factor for eutrophication is the excessive discharge of ammonia nitrogen. Unfortunately, traditional methods to remove ammonia nitrogen are ineffective when facing gradually strict rules. Recently, adsorption has gained interest from scholars due to its efficiency and safety in ammonia nitrogen treatment. In this study, a novel biochar, modified with magnetic iron, was synthesized through co-precipitation, which performed well in ammonia nitrogen removal. The maximum adsorption amount at 293 K of the composite that was synthesized at 80â(MB80) was 17.52 mg·g-1. Meanwhile, the simulation results displayed a good fitting with the pseudo second order model and Langmuir model. Additionally, the adsorption mechanism could be attributed to electrostatic adsorption, porous filling, ion exchange, and hydrogen bonding. Noticeably, MB80 maintained a good performance after 5 cycles, with desirable adsorption amount of 3.18 mg·g-1. This study aimed to provide an efficient method to treat ammonia nitrogen as well as a new way to dispose of municipal sludge.
RESUMEN
The excessive discharge of phosphate into natural water has caused serious environmental problems. Adsorption is an efficient technology for phosphorus removal from water. In this study, a novel biochar modified by chitosan, ferrous sulfate, and sodium sulfide was synthesized and performed well in phosphorus adsorption. The results of batch experiments showed that the optimum synthesized composite could adsorb 49.32 mg·g-1 of phosphate at 298 K. Meanwhile, the simulation results showed better fitting with the pseudo-second-order model and Langmuir model. The adsorption rate was dominated by three-dimensional diffusion within the inner pores. The adsorption process was defined as physic/chemisorption, while the adsorption mechanism was concluded to be electrostatic adsorption, porous filling, surface chemical precipitation, hydrogen binding, and the ligand effect. This study showed that the composite is effective in phosphorus removal from water, and we anticipate that our research will offer guidelines for adsorbent design and reveal the adsorption mechanism.