Industrial Pretreatment Program
The Downriver Sewage Disposal System (DSDS) transports and treats wastewater from over 500 industrial facilities in the Service Area. The Industrial Pretreatment Program or “IPP” is the mechanism that regulates these discharges in accordance with State and Federal environmental regulations. The goals of the IPP are:
- Prevent the introduction of wastes which may interfere with normal operation of the interceptor sewers, the wastewater treatment plant or the handling and disposal of biosolids generated during the treatment process;
- Prevent the pass through of industrial pollutants that may not be removed at the treatment plant, and the discharge of those pollutants into the Detroit River;
- Improve opportunities to recycle and reclaim industrial wastewater and sludge from the treatment plant;
- Protect the health and safety of sewer system employees and citizens of Wayne County from potentially adverse discharges.
There are 42 “Significant Industrial Users” or “SIUs" served by the DSDS. The SIUs are the subset of industries whose wastewater quantity exceeds a federally-specified flow rate, or whose industrial process falls into a category of facilities identified by U.S.EPA as requiring regulation. All SIUs receive a permit which specifies the allowable discharges into the DSDS, with site specific limits for pollutants. The permits also impose self-monitoring requirements on the SIU, and DSDS staff perform site inspections to verify compliance.
In order to achieve the IPP goals, the DSDS has adopted regulations to strictly limit the discharge of pollutants that may be found in industrial waste at concentrations that may be problematic. The DSDS has established “local Limits” for the following 32 pollutant parameters of concern:
|Barium||Nickel||Bis (2-ethylhexyl) phthalate||Trichloroethylene|
|Cadmium||Thallium||Tetrachloroethylene||Fats, Oil & Grease (FOG)|
|Cyanide||Mercury||Ethylbenzene||Total Suspended Solids (TSS)|
The Industrial Pretreatment Program is currently administered by Wayne County, but the IPP will transfer to the Downriver Utility Wastewater Authority as part of the Authority’s acquisition of the System.
Biosolids Handling and Disposal
Biosolids, which are sometimes commonly referred to as “sludge”, are a byproduct of the wastewater treatment process. Basically, pollutants are removed from the liquid stream by the treatment plant, and these are captured, collected, dried and disposed of in accordance with State and Federal environmental regulations. As the second largest municipal wastewater system in Michigan, the Downriver Sewage Disposal System generates a significant quantity of biosolids which must then be carefully handled. Failure to effectively remove and dispose of biosolids can result in environmental problems and permit violations due to excess suspended solids in the discharge from the treatment plant to the Detroit River.
On average, the Downriver Sewage Disposal System generates and disposes of more than 100 tons of sludge cake per day from the wastewater plant. Managing and disposing of biosolids is a significant operating expense for the System, and one that is subject to increase in the future due to anticipated changes in market conditions affecting haulers and landfills.
The basic process used by the DSDS is to pump the biosolids generated in the primary and secondary treatment processes to the Solids Complex where it can be stored, thickened and dewatered prior to disposal. Dewatering is accomplished by two Belt Filter Presses and two Centrifuges. Polymers are added to aid the dewatering process and achieve a dryer sludge cake. The dried sludge cake is loaded onto closed containers which are then hauled to a licensed landfill for disposal. The hauling and disposal work is handled by an independent contractor based on competitive bids.
The Sludge Hauling/Disposal Contract currently being used by the DSDS is with Stansley Industries and the contract runs through July, 2017.