Phytoremediation potentiality of garlic roots for 2,4-dichlorophenol removal from aqueous solutions.

2,4-Dichlorophenol (2,4-DCP) is considered as an important pollutant because of its high toxicity and wide distribution in wastewaters. Innocuous remediation technologies have been studied for the removal of this pollutant. This study investigated the feasibility of using garlic roots as a plant system for the removal of 2,4-DCP. The optimal conditions for its removal were established based on orthogonal experiments (OA25 matrix). Significant factors that affect removal efficiency, arranged from high to low importance, include pH, reaction time, 2,4-DCP concentration, and H2O2 concentration. In addition, garlic roots could be re-used for as much as three consecutive cycles. The decrease in pH and the increase of Cl(-) ion content in the post-removal solutions indicated that 2,4-DCP dehalogenation occurred during transformation. Changes in the deposition pattern of lignin in roots exposed to 2,4-DCP suggested that several of the products deposited were lignin-type polymers. The acute toxicity test revealed that the post-removal solutions were less toxic than the parent solutions. Therefore, garlic roots have considerable potential to effectively and safely remove 2,4-DCP from wastewater.

[Efficiency analysis of two-stage SBR for phosphorus nitrogen and organic substrate removal].

Taking simulated domestic sewage as treatment object, the characteristics of separate-stage phosphorus, organic substrate and nitrogen removal were studied in two-stage SBR by contrast experiment and mechanism analysis under the normal temperature, its efficiency-predominance was analyzed. The results indicate that the heterotrophic PAOs and nitrobacteria can be dominant growth in individual reactor respectively, under the effluent quality is more superior, the treatment efficiency is one time higher than that in the single SBR by controlling the sludge age (the phosphorus removal stage 5-7 d, the nitrogen removal stage about 50 d). The two-stage SBR can relieve the attack of organic load to nitrification process effectively, its nitrogen removal stage (SBR2) can still maintain stable nitrification rate under the higher COD concentration and the final effluent of the system is easy and stable to reach national standards (TP < or = 0.5 mg x L(-1)). In addition, the nitrogen removal stage (SBR2) of two-stage SBR not only can maintain nitrobacteria predominant, but also can cultivate heterotrophic bacteria which can remove difficult degraded organic substrate, that results in lower COD concentration than in the single's at the end of nitrification.