BENEFICIAL UTILIZATION OF BIOSOLIDS AT THE METROPOLITAN WATER RECLAMATION DISTRICT OF GREATER CHICAGO
Abstract:The mission of the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC), is to keep sewage pollution out of Lake Michigan, the area's prime drinking water supply, and to properly treat sewage to avoid contamination of the Chicago, Des Plaines and Illinois Rivers. The District treats an average of 1.5 billion gallons of industrial and domestic wastewater per day. The daily treatment capacity at its seven Water Reclamation Plants (WRPs) exceeds two billion gallons. The wastewater treatment process utilized at the WRPs results in the generation of approximately 190,000 dry tons of biosolids each year, in addition to clean water. The disposal or utilization of this large volume of biosolids, which has increased due to increasing industrialization and improved treatment technologies, is an ongoing challenge to the MWRDGC. The promulgation of 40 CFR 503 - Standards for the Use or Disposal of Sewage Sludge, has dictated the quality of biosolids required for legal disposal or utilization.
With the advent of the 40 CFR 503 regulations, the MWRDGC, in order to meet the high quality biosolids standards required for land application programs, initiated the so-called 503 Enforcement Initiative (503 EI). The thrust of the MWRDGC's 503 EI program was to produce high quality biosolids through substantial reductions in the discharge of heavy metals present in the wastewater discharged from Industrial Users (IUs), to below those metal levels specified in Table 3 of Sec. 503.13. The MWRDGC's existing Pretreatment Program was intensified by increased monitoring of industrial point source discharges into the MWRDGC's sewerage system and providing innovative pollution prevention (P2) assistance to the industrial community. The 503 EI Program was overwhelmingly successful in achieving the objective of ensuring low metals concentrations in MWRDGC biosolids, which allows for opportunities for beneficial reuse. Through the 503 EI, the MWRDGC was able to reduce the discharge of total metals of concern from categorically regulated IUs more than 40 percent. Improved pretreatment enforcement efforts significantly minimized the introduction of toxic metals to MWRDGC WRPs, and assured that the metals concentrations in the biosolids produced would comply with the limits in Table 3 of Sec. 503.13, a requirement for exceptional quality (EQ) biosolids.
In addition to achieving the metals limits, the produced biosolids must also meet certain pathogen requirements which further dictate utilization methods. To assure the pathogenic kill required for EQ biosolids, referred to as Class A, the MWRDGC employs a unique sludge processing strategy which provides a dry (60% solids) product. The MWRDGC is actively pursuing certification of two of its processing trains as a process equivalent to a process to further reduce pathogens (PFRP), with the United States Environmental Protection Agency (USEPA).
The MWRDGCs biosolids utilization program emphasizes maximizing environmentally safe, beneficial recycle for farmland application and public uses. This program conserves natural resources and results in one of the more economical methods for final utilization. However, public concern and misinformation about the health and environmental risks associated with biosolids land application can result in opposition from residents and local communities. The MWRDGC realizes that these barriers may have more impact on its biosolids program than the regulations imposed by local, state and federal agencies. In order to overcome these potential barriers, the biosolids contractor and MWRDGC staff must actively seek to educate the disaffected citizenry. Public perception could be improved by disseminating scientifically accurate information. In order to improve relations and understanding with the local communities' which are receiving biosolids for land application, the MWRDGC requires biosolids contractors to employ a full time public relations coordinator to provide education and outreach programs. These efforts must include scheduling meetings with the local communities' public, political and agricultural leaders, as well as affected citizens, to promote its beneficial reuse program; tours of biosolids utilization sites must be offered and an annual report summarizing the contractor's public relations activities made available to the public; distribute information documenting the benefits of the biosolids utilization program.
In order to diversify its biosolids disposal/utilization options and to become less dependent on the seasonal factors in the production of biosolids, the MWRDGC plans to process about 25% of its biosolids production using a heat drying process.
The disposal of large quantities of biosolids in a cost effective manner without compromising the health and safety of people or the environment, in addition to fostering positive public perception of the beneficial reuse of biosolids, is an enormous ongoing challenge. The MWRDGC continues to successfully and economically achieve this goal.
Document Type: Research Article
Publication date: January 1, 2002
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