The aim of this study was to analyse the impact of velocity in the hydroponic lagoon used as the 3rd stage of municipal wastewater treatment on washing out of the particles suspended in the sewage as well as settled on the bottom of the hydroponic ditch. In order to analyse the flow velocity in the lagoon, 12 cross-sections were determined at points where the speed and motion of particles can change. Wastewater samples were taken in the summer month from each of the 12 sampling points (the depth of 0.1 m) and the basic physicochemical parameters of sewage were determined (BOD5, COD, TOC, TSS, turbidity). In selected cross-sections, a granulometric analysis of particles was made to determine the characteristics of suspended solids in the wastewater flow path. Based on the analysis, it was found that velocities in the lagoon during aeration can be ten times higher (0.070 m·s⁻¹) than those assumed by designers (0.006 m·s⁻¹). Such a large difference means that the sedimentation conditions assumed in the project cannot be met, which may result in an increase in the total suspended solids and organic matter concentrations at the outflow to the receiving water body. During the flow through the hydroponic ditch, the highest efficiency of pollutant removal was indicated for BOD5 — 88.7% and TSS — 80%, while the COD removal occurred with the lowest efficiency — 34.1%. Improving flow conditions as designed in the hydroponic lagoon technological project may increase the efficiency of wastewater treatment at the third stage of treatment.

本研究的目的是分析用作城市废水处理的第三阶段的水培泻湖中的速度对冲洗掉悬浮在污水中以及沉淀在水培沟底部的颗粒的影响。为了分析泻湖中的流速，在粒子的速度和运动可以改变的点处确定了 12 个横截面。夏季月份从12个采样点（深度0.1 m）中的每一个采样点抽取废水样品，并测定污水的基本理化参数（BOD5、COD、TOC、TSS、浊度）。在选定的横截面中，对颗粒进行粒度分析以确定废水流路中悬浮固体的特性。根据分析，^-1 ) 比设计者假定的那些 (0.006 m·s ^-1 )。如此大的差异意味着无法满足项目中假设的沉淀条件，可能导致受纳水体出流处的总悬浮物和有机物浓度增加。在流经水培沟的过程中，BOD5 的污染物去除效率最高为 88.7%，TSS 为 80%，而 COD 的去除效率最低，为 34.1%。改善水培泻湖技术项目中设计的流动条件可能会提高污水处理第三阶段的效率。