Introduction

Due to the population growth and reduction of water resources, wastewater treatment and reuse vital. As the secondary wastewater treatment processes enable removes a significant amount of P and N, nutrient-rich effluents can cause eutrophication in water bodies. On the other hand, nutrients removal in sewage treatment using mechanical methods is costly and complex. The aquaculture method using Azolla filiculoides could be an appropriate option for removing total phosphorus (TP), total nitrogen (TN), and chemical oxygen demand (COD) from wastewater.

Materials and methods

Synthetic wastewater has been prepared in the typical range of municipal wastewater. Two g fresh weight of an acclimatized A.filiculoides was floated in sample bowls each one containing 500 CC prepared wastewater. Total nitrogen, TP, and COD removal by Azolla filiculoides for 21-days were optimized and investigated using the response surface methodology (RSM). For this aim, the D-optimal method was used to optimize the three independent variables (TP concentration (10.8–84.6 mg l^− 1), TN concentration (20–99 mg l^− 1), and COD concentration (66.26–415 mg l^− 1)) for their maximum removal efficiency of them. Experiments were performed on 28 runs in which independent variables were measured using a HACH DR 5000 spectrometer.

Results

Predicted R-squared for COD, TP, TN removal, and Azolla mass (responses) have been equal to -0.0897, 0.8514, 0.7779, and 0.5645, respectively. The model was used to maximize Azolla growth and maximize removal efficiency of nitrogen, phosphorus, and COD that occurred in minimum concentrations of TN (20 mg l^− 1), TP (10.8 mg l^− 1), and COD (66.26 mg l^− 1). The removal efficiency of Azolla was obtained 77.5 % for COD, 66.8 % for TP, and 78.1 % for TN in the optimum condition of independent variables. Also, increase of Azolla mass was 239 %, with desirability of 0.66. The difference between model prediction and model validation testing for Azolla mass increase, COD, TN, and TP removal was equal to ± 11.6 %, ± 7.9 %, ± 0.0 %, and ± 1.9 %, respectively.

Conclusions

Azolla could remove phosphorus in nitrogen deficiency or even lack of nitrogen. Results indicate that removal efficiency has an upward trend as the Azolla growth increases. This kind of fern has a significant effect on removing nitrogen, phosphorus, and COD from an aqueous solution. The removal efficiency of TN, TP, and COD at optimum operating conditions showed good agreement with model-predicted removal efficiency.

中文翻译：

---

使用响应面法对满江红处理废水进行建模

介绍

由于人口增长和水资源减少，废水处理和再利用至关重要。由于二级废水处理工艺能够去除大量的 P 和 N，因此富含营养的废水会导致水体富营养化。另一方面，使用机械方法去除污水中的营养物质既昂贵又复杂。使用满江红的水产养殖方法可能是去除废水中总磷 (TP)、总氮 (TN) 和化学需氧量 (COD) 的合适选择。

材料和方法

合成废水已在典型的城市废水范围内制备。将 2 g 鲜重的驯化A.filiculoides漂浮在样品碗中，每个样品碗中装有 500 CC 制备的废水。使用响应面法 (RSM) 优化和研究满江红21 天对总氮、TP 和 COD 的去除。为此，使用 D 最优方法优化三个自变量（TP 浓度（10.8-84.6 mg l ^-1）、TN 浓度（20-99 mg l ^-1）和 COD 浓度（66.26-415 mg l ^{- 1})) 因为它们的最大去除效率。在 28 次运行中进行了实验，其中使用 HACH DR 5000 光谱仪测量了自变量。

结果

COD、TP、TN 去除和满江红质量（响应）的预测 R 平方分别等于 -0.0897、0.8514、0.7779 和 0.5645。该模型用于最大限度地提高满江红的生长，并最大限度地提高氮、磷和 COD 的去除效率，这些在 TN (20 mg l ^{- 1} )、TP (10.8 mg l ^{- 1} ) 和 COD (66.26 mg l ^{- 1} )。在自变量最佳条件下，满江红的COD去除率为77.5%，TP为66.8%，TN为78.1%。此外，满江红的质量增加了 239%，合意度为 0.66。满江红模型预测和模型验证测试的区别质量增加、COD、TN 和 TP 去除率分别等于 ± 11.6 %、± 7.9 %、± 0.0 % 和 ± 1.9 %。

结论

满江红可以在缺氮甚至缺氮的情况下去除磷。结果表明，随着满江红生长的增加，去除效率呈上升趋势。这种蕨类植物对去除水溶液中的氮、磷、COD有显着的效果。在最佳操作条件下 TN、TP 和 COD 的去除效率与模型预测的去除效率非常吻合。