About Our Facility
 
The Portage Lake Water & Sewage Authority (PLWS&A) was established in 1964 by the cities of Hancock and Houghton for the purpose of constructing and operating a joint use wastewater treatment facility. The facilities that were constructed included a lift station for each city to convey wastewater to a common site and a wastewater treatment plant located on the south shore of Hancock.

Planning was initiated by the PLW&SA in 1987 when it became evident that the existing treatment plant was operating at flows in excess of the design flow and was not able to treat all of the excess flow that was being generated by both cities.

TKDA and U.P. Engineers and Architects were retained to prepare a facility plan to determine the rehabilitation and possible expansion necessary to provide treatment of all the wastewater flow generated by the two committees. The State DNR established the criteria that all the wastewater generated must receive treatment to meet the effluent plant limits.

The facility plan determined that the most cost effective and environmentally sound long-term plan was to construct a new treatment facility on the Houghton sands site. Construction of this facility is complete and it has been placed into operation. This treatment plant has the capacity to treat wastewater flow up to 18 MGD during wet periods of snowmelt and rainfall.


Wastewater Conveyance Components
Lift Stations and Forcemain. The Hancock lift station at the old treatment plant has been remodeled to serve as a lift station to pump Hancock's wastewater across the canal to the Houghton lift station. The Houghton lift station was also remodeled so that it pumps the combined flow of both cities through a 24-inch forcemain to a 48-inch gravity interceptor, which conveys all of the wastewater to the new treatment plant.

Influent Pumping
Wastewater that arrives at the treatment plan is lifted by screw pumps through the treatment units and to Portage Lake.

Pretreatment
Pretreatment consists of screening and grit removal. The mechanically cleaned bar screen removes coarse solids from the flow. The aerated grit chambers remove sand, gravel and heavy grit to protect the downstream treatment units.

Primary Clarification
The primary clarifiers remove a significant portion of the suspended solids from the wastewater. These tanks allow solids to settle slowly to the bottom of the tank by gravity. Settled solids are collected at the bottom of the tanks and pumped as "sludge" to the anaerobic digestors.

Secondary Treatment (Activated Sludge)
Secondary treatment is a biological process that is used to remove organic material present in the wastewater. The biological process utilized is called activated sludge. Aerobic (oxygen-demanding) bacteria grow in these tanks and consume the organic materials in the wastewater. This process is accomplished in the secondary aeration tanks and the secondary clarifiers. After aeration, the bacteria-laden solids are separated in the secondary clarifiers and a portion is returned to the aeration tank. This arrangment of "return sludge" allows the operator to control the amount of bacteria present in the process. Excess solids are wasted to the primary clarifiers where it is combined with the primary solids.

Disinfection
Ultraviolet (UV) disinfection is the final treatment of the wastewater. Disinfection is accomplished by an innovative process that utilizes high dosages of ultraviolet light to eliminate any potentially harmful pathogenic organisms that could be present in the wastewater. A specific wavelength of ultraviolet light is germicidal and is used to destroy nearly all of the bacteria that are present.

Discharge
An underground pipeline carries the treated effluent to discharge by a 100 foot long diffuser into Portage Lake.

Anaerobic Digestion
Anaerobic digesters process the sludge removed from the clarifiers to produce methane gas and biosolids fertilizer. The Primary Digester is heated and mixed to foster the growth of anaerobic methanogenic bacteria. The Secondary Digester separates the biosolids from the liquid. Anaerobic digestion converts most of the organic material in the sludge to methane gas and produces biosolids that are relatively odor free and suitable for land application as a fertilizer.

Biosolids Dewatering and Storage
The biosolids are dewatered by belt filter presses to a moist state containing about 16% solid material by weight. The dewatering step removes water and reduces the volume to be hauled to land application. A storage facility provides storage of dewatered biosolids between periods of land application.

Land Application of Biosolids Fertilizer
The processed biosolids are applied as a soil fertilizer and amendment to assist in vegetation of the Mason stamp sands . Biosolids are also applied to assist in fertilizing local agricultural and wildlife areas in accord with MDEQ requirements.

 
 
100 Princess Point Drive t. 906.487.9820
Houghton, Michigan 49931 f. 906.487.9474
   

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