DWSD Sludge and NEFCO

Throughout its existence, the Detroit Water & Sewerage Department (DWSD) has disposed of most of its sewage sludge (aka biosolids) by incineration or in landfills.  (Small amounts have gone to farms as fertilizer.)

The high cost of maintaining and rebuilding the incinerators, more strict air quality standards and limitations imposed by landfills caused DWSD in 2013 to contract with the New England Fertilizer Company (NEFCO) to design, build and operate a plant in Detroit to dry and pelletize a significant portion of the sludge for use as fertilizer and power plant fuel.  

NEFCO photo: construction in Detroit

Under DWSD’s contract with NEFCO, sewer system ratepayers will be on the hook for nearly $700,000,000 over 20 years.

Last month, DWSD executive director Sue McCormick reported that substantial completion of NEFCO’s Detroit facility is expected this month (December 2015).

The NEFCO plant will replace the six oldest of 14 incinerators.  The facility is expected to process incoming sludge at a modest rate of 300 (relatively dry) tons per day (dtpd), 400 in a pinch.  DWSD’s average sludge production the past year has been about 400 dtpd.  (If memory serves, sludge production was required to be at least 450 dtpd under the Second Amended Consent Judgement when DWSD was overseen by a federal judge.)

The daily tonnage that isn’t removed from wastewater ends up in the Detroit River and then Lake Erie.  So, if there are 550 tons of biosolids in the wastewater on the average day and DWSD removes 400 (perhaps 300 of which will go to NEFCO for pelletizing; 100 incinerated), that means that the remaining 150 tons daily or 54,750 tons annually will feed the algae in Lake Erie. (If there’s more to this calculation than meets the eye, DWSD hasn’t been forthcoming about it.)

There are plans to phase out the remaining eight incinerators in ten years. That’s enough time to install around the region several Janicki wastewater processors, which produce pure water, significant amounts of electricity and a small pile of ash (NO sludge).  The Detroit wastewater treatment plant and the NEFCO facility would no longer be necessary.

*****     **jl**     *****

Septic Systems and Water Quality

September 21-25  is the U.S. Environmental Protection Agency’s Third Annual SepticSmart Week.

During SepticSmart Week, EPA seeks to inform homeowners on proper septic system care and maintenance, assist local agencies in promoting homeowner education and awareness, and educate local decision makers about the infrastructure options available to improve and sustain their communities.

http://water.epa.gov/infrastructure/septic/Septic-Smart-Week.cfm

The Michigan Department of Environmental Quality (MDEQ) quotes a Rouge River Wet Weather Demonstration Project document to explain septic systems: (excerpts)

Septic systems are waste water treatment systems that use septic tanks and drainfields to dispose of sewage. They are typically used in rural or large lot settings where a sanitary sewer is not available...

A septic system usually is made up of a septic tank and a drain field. The septic tank is usually made of reinforced concrete, is buried and watertight. This tank receives untreated household waste. The drain field consists of a series of perforated pipes (pipes with holes in them), which distribute the liquid from the septic tank to the surrounding soil.

Although even the best designed and installed system will eventually fail, proper maintenance will ensure a longer lasting waste disposal system…

When waste enters the tank, bacteria begin to break down the solid materials. This break down reduces solids, but also leaves a residue behind in the tank. As time passes, this residue builds up, and must be removed to prevent it from entering the drainfield and clogging the system. The center liquid layer flows slowly from the tank into the drainage field. Perforated pipes allow the liquid to be equally distributed in a gravel-filled disposal field. Once the liquid reaches the disposal field, it soaks into the soil. The soil then acts as the final filter for treatment of waste received from the septic system.

https://www.michigan.gov/documents/deq/ess-nps-savvy-septic_209509_7.pdf

Onsite sewage disposal (septic) systems are common in southeast Michigan. In Oakland County, for example, there are more than 80,000 such systems.

According to the Oakland County Health Division, “...proper disposal of solid, liquid and sewage wastes is crucial to prevent contamination to the land and the groundwater below. The use of sewers and municipal sewage treatment plants is limited to areas where infrastructure exists. On-site sewage disposal is the only viable alternative in areas not serviced by municipal sewers.”

The Health Division’s Environmental Health Services Unit issues “...permits and conducts construction and final inspections for the installation of residential and non residential on-site sewage disposal systems…”

https://www.oakgov.com/health/services/Pages/Septic.aspx