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5.22.2010

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Project location

The PROBLEM

A Community that has 200 homes is connected to a septic tank with a failed leeching field for their waste treatment. The failed system is causing the waste to be discharged without adaquate treatment. The untreated water is currently routed into a stream which is used by local farmers for irrigation. The system requires redesign of current components and design of additional components.

 

lOCATION

The Community of Carabuela, Ecuador is located in the northern portion of the nation of Ecuador. It is located about a 2 hour drive from the capital city of Quito.

SMALLMAP

THE DESIGN

Grit Chamber

Grit Removal follows the unit process of screening and removes grit (heavy metals and sand) as to prevent any unnecessary abrasion of equipment downstream and accumulation of grit in the biological processes downstream. With the high presence of grit in combined sewer, it is necessary to achieve the appropriate levels of removal for our customer. Grit materials have a greater settling velocity than do organic materials and therefore can be removed without removing organics, which are needed for the digestion process downstream in the Imhoff tank or waste stabilization lagoons.

GRIT

Imhoff Tank

The Imhoff tank was invented and patented by a German engineering named Karl Imhoff in 1906. The tank combines two wastewater treatment processes, sedimentation and biological digestion, into one physical system. The tank is typically a two-story system in which simple sedimentation and anaerobic digestion are used to treat the influent wastewater. The upper story uses simple discrete particle settling as the driving force to remove particulate from the stream. The lower story uses anaerobic digestion to change the physical, chemical and biological properties of the settled sludge.

IMHOFF

Stabilization Lagoon

The third process of the wastewater system involves a stabilization pond, which will reduce large amounts of BOD, COD and TSS in the waste stream. Stabilization ponds can either be aerated, anaerobic or aerobic.


The stabilization pond of our choice will be placed at a location 500 meters away from the original septic tank. The vertical drop in this distance is about 1%, which means that the waste stream entering the lagoon will be 5 meters below the point at which waste stream leaves the Imhoff Tank. Because of the landscape in this region, an inverted siphon is required. An inverted siphon is the makeup of a sewage pipe that goes under an obstruction. The wastewater will flow under pressure in this particular section.

LAGOON

Drying Beds

After each treatment process, the sludge produced will need to be treated.  Often this involves aerobic or anaerobic digestion, but with an Imhoff tank this is done during the settling stage.  The sludge will be piped to the dewatering stage.  This decreases the volume by up to three-quarters and makes the sludge handle as a solid. The sludge will have to be removed approximately every twenty years and incinerated, brought to a landfill, or used as fertilizer.

DRYINGBED

 


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