ASABE Technical Library - Abstract
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TREATING HIGHER-STRENGTH COMMERCIAL SEWAGE FOR DISPOSAL OR RE-USE
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 701P0104, . (doi: 10.13031/2013.15820)Authors: E. C. Jowett
Keywords: wastewater treatment, aerobic treatment, high-strength sewage, re-claimed water, nitrogen removal, pre-engineered design, waste utilization, subsurface disposal
Commercial high-strength sewage can have surprises like high organics and nitrogen, variable
diurnal and seasonal flows, use of disinfectants and grease-strippers, or untrained employees. A
pre-engineered treatment process developed to counter these challenges results in a more
consistent effluent quality. Consistency is important for nitrogen removal, for difficult disposal
sites, or for re-use of effluent in irrigation or toilet flushing.
The standard treatment process for this high-strength sewage includes an exterior grease trap,
septic tanks with effluent filters, surge flow storage in the pump tank, timed dosing to Waterloo
trickle filters, and 50-67% re-circulation to the septic tank inlet. For on-site subsurface disposal,
a shallow, thin Area Bed made of medium-fine sand is preferred for optimum fecal coliform
removal which is near zero, even at high loading rates. For irrigation re-use, ultraviolet
disinfection is added for irrigation re-use, and multi-media filtration plus ozone and chlorine are
added for toilet re-use.
The additional key component is a separate, closed-loop BIOFILTER with 100% return to the
surge-pump tank. This independent BIOFILTER is hydraulically loaded at very high rates to
remove organics and nitrogen, and to oxygenate the pump tank. Median effluent values in the
first few months at five commercial sites are <10 mg/L cBOD and TSS, even though influent
sewage is variable and high-strength.
With maturity, the nitrate-N to TN ratio approaches 1.0, and nitrogen removal increases to 40-
80% by septic tank re-circulation alone, being higher with higher organic strength. The use of
ammonium-based cleaners can raise influent to >500 mg/L TKN.
For resort facilities such as golf courses and campgrounds, with a low flow followed abruptly by
a high flow, the system requires quick ramp-up with little to no deterioration in effluent quality.
The ClubLink golf courses are characterized by a step-function increase of 5-7 times within a
week or two, and the BIOFILTERS have been designed to successfully pass this hurdle.
A new highway truck stop includes the 100% loop in two self-contained Waterloo SC-40
BIOFILTERS (ISO containerized), with the chlorinated effluent being re-used for toilet flushing in
the facility, which is an estimated 60-70% of the water use. Groundwater shortages, nitrogen
contamination of groundwater, and real estate savings are all factors in choosing re-use.