Study on influencing parameters and long-term operation of electrocoagulation phosphorus removal from small rural domestic sewage.

Excessive discharge of phosphorus can produce eutrophication in aquatic environments, damaging public health, the living environment, and the economy. The conventional mechanical-biological phosphorus removal methods are not suitable for small rural domestic sewage due to the features of small scale, scattered distribution, intermittent emission, and large fluctuation. This work evaluated electrocoagulation (EC) with industrial steel as electrodes on small rural domestic sewage. Results showed that the best performance was achieved at a current density of 1 mA/cm2, electrode distance of 2 cm, electrode number of 2, pH of 7, and Hydraulic Retention Time of 30 min, respectively. Under optimum conditions, the EC process removed 93.91% phosphorus while consuming around 0.25 kWh/m3 of electricity. In addition, the electrode passivation of EC was further investigated; the long-term research found that the phosphorus removal efficiency only decreased by 4.34% after 10 days of continuous flow operation, and the operational energy consumption was 0.07 kWh/m3 at a Cl- concentration of 500 mg/L.

[Removal pathway and influence factors of hydroponic bio-filter method for nitrogen and phosphorus].

Study was made on the use of hydroponic bio-filter method (HBFM) for eutrophic surface water. Results show that HBFM can remove 16.8% of TN and 30.8% of TP at the hydraulic loading rate (HLR) of 3.0 m3/(m2 x d). The removal loading rate of TN and TP can accordingly reach 1.0 and 0.1 g/(m2 x d) respectively. The sedimentation of particulate nitrogen and particulate phosphorus plays a major role in nitrogen and phosphorus removal, and its contribution is 62.2% and 75.9% respectively. The optimal HLR of HBFM ranges from 3.0 to 4.0 m3/(m x d). The intension of secateur for Nasturtium officinale has some effect on its uptake rate, thus the length of cut when harvesting should be less than 10 cm. The harvesting frequency of once a month for Nasturtium officinale has no effect on nitrogen and phosphorus removal of HBFM.