Data for: Long-Term Trends Show Improvements in Water Quality in the Chicago Metropolitan Region with Investment in Wastewater Infrastructure, Deep Tunnels, and Reservoirs

Compiled water quality data of the Chicago, Calumet, and Des Plaines River Systems from 1975 to 2018. Data were collected as part of the Metropolitan Water Reclamation District's Ambient Water Quality Monitoring program. A study was carried out to evaluate water quality trends from 1975 to 2012 and from 2013 to 2018 in the Chicago, Calumet, and Des Plaines River Systems in Cook County, Illinois, in order to investigate the outcome of practices carried out by the Metropolitan Water Reclamation District of Greater Chicago. Data from 41 monitoring locations were compiled and analyzed for 11 water quality parameters. The seasonal Kendall test was performed on each variable at each location to analyze for long-term monotonic trends. Wilcoxon Rank-Sum test was used to test for significant differences in water quality constituents between time periods to point to practices that changed water quality during the study period. For most sampling locations, long-term trend analyses showed significant downward trends for total organic carbon (TOC), total Kjeldahl nitrogen (TKN), ammonium nitrogen (NH4-N), total suspended solids (TSS), fecal coliform (FC), and sulfate and significant upward trends for dissolved oxygen (DO), chloride, and temperature. Total phosphorus (TP) concentrations increased downstream of the Stickney, Kirie, and Calumet WRPs from 1975 to 2012, but decreased downstream of the Kirie WRP and had no trends downstream of the Stickney and Calumet WRPs from 2013 to 2018. Improvements in TKN, NH4-N, TOC, TSS, FC, TP, and DO concentrations over four decades demonstrated the beneficial outcome from the expansion of secondary treatment systems at water reclamation plants, implementation of the Tunnel and Reservoir Plan System, instream and side-stream elevated pool aeration stations, and effluent disinfection.

The study is described in the article entitled "Long-Term Trends Show Improvements in Water Quality in the Chicago Metropolitan Region with Investment in Wastewater Infrastructure, Deep Tunnels, and Reservoirs". Supporting Information for this manuscript is attached.

汇编自1975年至2018年芝加哥、卡尔梅特和德普莱恩斯河流域水质数据。该数据作为大芝加哥都会区水再生区环境水质监测计划的一部分进行收集。本研究旨在评估1975年至2012年及2013年至2018年间，位于伊利诺伊州库克县的芝加哥、卡尔梅特和德普莱恩斯河流域水质变化趋势，以探究大芝加哥都会区水再生区实施措施的影响。对41个监测点的11个水质参数数据进行汇编和分析。在每个监测点对每个变量执行季节性肯德尔检验，以分析长期单调趋势。使用威克森秩和检验来检测不同时间段内水质组成成分的显著差异，以指明在研究期间改变水质的措施。对于大多数采样点，长期趋势分析显示总有机碳（TOC）、总凯氏氮（TKN）、氨氮（NH4-N）、总悬浮固体（TSS）、粪便大肠菌群（FC）、硫酸盐呈显著下降趋势，而溶解氧（DO）、氯化物和温度呈显著上升趋势。从1975年至2012年，磷酸盐（TP）浓度在斯ティ克尼、基里和卡尔梅特水再生区下游增加，但在基里水再生区下游减少，从2013年至2018年在斯蒂克尼和卡尔梅特水再生区下游没有趋势。在四十年间，TKN、NH4-N、TOC、TSS、FC、TP和DO浓度的改善展示了水再生厂扩大二级处理系统、实施隧道和水库计划系统、河内和侧流高水位曝气站以及排放消毒的益处。

本研究以《长期趋势显示，在投资废水基础设施、深隧道和水库后，芝加哥都市区域水质得到改善》为题发表于文章中。本文的补充信息已附于稿件之中。