Wastewater stabilization ponds (WSP) are a common method to treat wastewater before release. The purpose of the current study was to find the most inexpensive coagulation and flocculation reagents to use during harvesting of WSP algae from effluent so that water without algae can be generated for irrigation purposes. In the study, the toxicity of effluent from the algae-based WSP system after treatment with alum and chitosan was investigated. The chemical composition of the resultant supernatants was tested in conjunction with a battery of bioassays (Daphnia magna, Allium cepa, Lactuca sativa and Triticum aestivum). The bioindicator organisms were exposed to varying concentrations of the supernatant resulting from harvesting the algae biomass with chitosan (0.368 g/L chitosan) and aluminium sulphate (9.96 g/L powder). Alum was lethal to D. magna, while chitosan did not seem to affect the Daphnia test specimens. Undiluted chitosan supernatant and 100% alum resulted in minimal inhibition of the rate of T. aestivum seed germination, while both resulted in significant inhibition of the L. sativa seed germination rates. Similarly, minimal effects were found for the root growth in T. aestivum, with significant root growth inhibition observed in L. sativa and A. cepa. In A. cepa, clear differences were observed in the inhibition of root growth when the two reagents were compared. The alum and chitosan supernatants had a total carbon, iron and sulphate concentration of 327.78 mg/L, 0.12 mg/L and 68.44 mg/L and 182.04 mg/L, 0.16 mg/L and 166.80 mg/L, respectively. Based on the test specimens’ response, chitosan as flocculation method was less toxic when compared with alum coagulation, even though both algae harvesting methods changed the chemical composition of the algae-treated water.

废水稳定池（WSP）是在排放前处理废水的常用方法。当前研究的目的是找到在从废水中收获WSP藻类时要使用的最便宜的混凝和絮凝剂，以便可以将不含藻类的水用于灌溉目的。在研究中，研究了用明矾和壳聚糖处理后，基于藻类的WSP系统产生的废水的毒性。结合一系列生物测定法（大水蚤，葱属，苜蓿和普通小麦）对所得上清液的化学组成进行了测试。）。将生物指示剂生物暴露于各种浓度的上清液中，这些上清液是通过用壳聚糖（0.368 g / L壳聚糖）和硫酸铝（9.96 g / L粉末）收获藻类生物质而得到的。明矾对D. magna致死，而壳聚糖似乎并未影响水蚤的标本。未稀释的壳聚糖上清液和100％的明矾导致对普通小麦种子发芽率的抑制作用最小，而两者均导致对苜蓿种子发芽率的显着抑制作用。类似地，发现对普通小麦的根生长影响最小，在紫花苜蓿和洋葱曲霉中观察到显着的根生长抑制作用。在比较两种试剂后，根茎A. cepa在根生长抑制方面观察到明显差异。明矾和壳聚糖上清液的总碳，铁和硫酸盐浓度分别为327.78 mg / L，0.12 mg / L和68.44 mg / L和182.04 mg / L，0.16 mg / L和166.80 mg / L。根据试样的响应，壳聚糖作为絮凝方法与明矾凝结相比毒性较小，即使两种藻类收获方法都改变了经过藻类处理的水的化学组成。