Long-term biosolids planning with an operational mega reservoir for combined sewer overflow-impacted stormwater capture.

The Metropolitan Water Reclamation District of Greater Chicago adopted the Tunnel and Reservoir Plan (TARP) to reduce combined sewer overflow (CSO) events in the Chicago region. The Thornton Composite Reservoir (TCR) became operational in 2015 providing an additional 30 million m3 of CSO-impacted stormwater capacity. In the United States, no other mega reservoirs are in operation to provide as a reference to study the long-term impacts of biosolids operations in water resource recovery facilities. The mean daily volume pumped from the Calumet TARP system to the Calumet Plant increased 144-238 m3 from 2012-2014 to 273-360 m3 from 2016-2018. Overall annual digester feed solids for the 2016-2018 post-TCR period were 28,182 Mg, which was 11 percent less than the mean for the 2012-2014 period of 31,745 Mg. Annual digester draw solids for the 2016-2018 post-TCR period were 19,422 Mg, which were 4 percent less than the 2012-2014 pre-TCR period mean of 20,190 Mg. This paper demonstrated a decrease in digester feed loading to the Calumet Plant and, ultimately, a decrease in digester draw solids with an overall increase in plant and TARP flow in the years following operation of the TCR for the capture and treatment of CSO-impacted stormwater. PRACTITIONER POINTS: Reservoirs capturing combined sewer overflow-impacted stormwater improve water quality of local waterways. Mega reservoirs may impact solids loading to water resource recovery facilities. Hydraulic loading to water resource recovery facilities may be substantial with mega reservoirs.

Prediction of odor complaints at a large composite reservoir in a highly urbanized area: A machine learning approach.

Odorous compound emissions and odor complaints from the public are rising concerns for agricultural, industrial, and water resource recovery facilities (WRRFs) near urban areas. Many facilities are deploying sensors that measure malodorous compounds and other factors related to odor creation and dispersion. Focusing on the Metropolitan Water Reclamation District of Greater Chicago's (MWRDGCs) Thornton Composite Reservoir (7.9 billion gallon capacity), we used meteorological, operational, and H2S sensor data to train a 3-day advance-warning predictor of local odor complaints, so as to implement targeted odor prevention measures. Using a machine learning approach, we bypassed difficulties in modeling both physical dispersion and human perception of odors. Utilizing random forest algorithms with varied settings and input attributes, we find that a small network of H2S sensors, meteorological data, and operational data are able to predict odor complaints three days in advance with greater than 60% accuracy and less than 25% false-positive rates, exceeding MWRDGC's standards required for full-scale deployment. PRACTITIONER POINTS: A random forest algorithm trained on H2 S, weather, and operations data successfully predicted odor complaints surrounding a large composite reservoir. Thirty-two data attribute combinations were tested. It was found that H2 S sensor data alone are insufficient for predicting odor complaints. The best predictor was a Random Forest Classifier trained on weather, operational, and H2 S readings from the reservoir corner locations. This study demonstrates odor complaint prediction capability utilizing a limited set of data sources and open-source machine learning techniques. Given a small network of H2 S sensors and organized data management, WRRFs and similar facilities can conduct advance-warning odor complaint prediction.

Evaluation of revolving algae biofilm reactors for nutrients and metals removal from sludge thickening supernatant in a municipal wastewater treatment facility.

This work is to evaluate pilot-scale Revolving Algal Biofilm (RAB) reactors of two heights (0.9-m and 1.8-m tall) to treat supernatant from sludge sedimentation at Metropolitan Water Reclamation District of Greater Chicago (MWRD) for removing nutrients (N and P) as well as various metals. The RAB reactors demonstrated a superior performance in N and P removal as compared to control raceway ponds. Taller 1.8-m RAB reactors performed better than 0.9-m RAB reactors in terms of total nutrient removal and algal biomass productivity. At 7-day HRT, total P (TP) and Total Kjeldahl N (TKN) removal efficiency reached to 80% and 87%, respectively, while ortho-P and ammonia removal efficiency reached to 100%. Decreasing HRT led to an enhanced TP and TKN removal rate and nutrient removal capacity. At HRT of 1.3-day, the TP removal per footprint of 1.8-m tall RAB reactors was around 7-times higher than the open pond system. The RAB reactors also showed certain capabilities of removing metals from wastewater. The study demonstrated that RAB-based treatment process is an effective method to recover nutrients from municipal wastewater.

Development of a comprehensive plan for utilization of digester gas moves towards energy self-sufficiency in Chicago, USA.

The Metropolitan Water Reclamation District (MWRD) of Greater Chicago's Stickney Water Reclamation Plant (SWRP) anaerobically digests approximately 430 dry tons per day (dtpd) (390 dry metric tons per day) of solids and produces 3.4 million ft(3)/day (96 thousand m(3)/day) of biogas from the anaerobic digesters, making it one of the largest municipal digester gas complexes in the world. Installation of new treatment processes, as well as future increases in flows and loads to the plant, are expected to significantly increase production of biologically degradable sludge and biogas. This paper presents a comprehensive planning study that was completed to identify and evaluate alternatives for utilization of this biogas. The best, sustainable approach was identified, taking into consideration economics, social impacts, and environmental impacts. The model results indicate that the most economically favorable scenario involves installing a cogeneration facility to produce electricity on-site, and operating it in conjunction with the plant's existing boilers to satisfy the heating needs of the plant. This scenario also provides the greatest reduction in GHG offsets at the power plants.

Sixty-five-year old final clarifier performance rivals that of modern designs.

The Stickney plant of the Metropolitan Wastewater Reclamation District of Greater Chicago (MWRDGC), one of the largest wastewater treatment plants in the world, treats an average dry weather flow of 22 m3/s and a sustained wet weather flow of 52 m3/s that can peak to 63 m3/s. Most of the inner city of Chicago has combined sewers, and in order to reduce pollution through combined sewer overflows (CSO), the 175 km Tunnel and Reservoir Plan (TARP) tunnels, up to 9.1 m in diameter, were constructed to receive and convey CSO to a reservoir from where it will be pumped to the Stickney treatment plant. Pumping back storm flows will result in sustained wet weather flows over periods of weeks. Much of the success of the plant will depend on the ability of 96 circular final clarifiers to produce an effluent of acceptable quality. The nitrifying activated sludge plant is arranged in a plug-flow configuration, and some denitrification takes place as a result of the high oxygen demand in the first pass of the four-pass aeration basins that have a length to width ratio of 18:1. The SVI of the mixed liquor varies between 60 and 80 ml/g. The final clarifiers, which were designed by the District's design office in 1938, have functioned for more than 65 years without major changes and are still producing very high-quality effluent. This paper will discuss the design and operation of these final clarifiers and compare the design with more modern design practices.