Wapsie Valley School
Two 20,000-gallon (75.7 m3) septic tanks
10,000-gallon (37.9 m3) recirculation tank
Four AdvanTex-AX100 pods
Two duplex 50 gpm, 3/4-hp (3.2 Lps, 0.6 kW) pump packages
TCOM telemetry control panel
Existing subsurface drainfield
Part-time operator with quarterly maintenance visits.
<10 mg/L BOD5
<10 mg/L TSS
<5 mg/L NH3-N
Challenging Conditions Require Innovative Solution
In 2004, Wapsie Valley School desperately needed a wastewater solution. Partially treated, odorous wastewater was surfacing from the school's 45-year old drainfield and flowing over the schools' parking lot. School officials hired MMS Consultants to evaluate options for a new system.
MMS had to design a system that could deal with the school's highly variable wastewater flows. In addition to serving 350 students and staff, the rural school also hosted community activities, including athletics, music programs, drama, and conferences. During the school year, wastewater flows averaged 5000 gpd (19 m3/d), and big events strained the system's capacity to a peak of 13,000 gpd (49.2 m3/d). But during the summer, flows dwindled to almost nothing. Most wastewater treatment technologies perform poorly when flows vary this much.
Another challenge for the treatment system was Iowa's winter temperatures, which typically approach 0° F (-18° C).
In addition to these challenges, MMS had to cope with construction constraints. Space on campus was limited, and school officials insisted on preserving existing athletic space and other areas throughout the school grounds. Only a small section of land, located within 20 feet (6 m) of classrooms, was available. Moreover, construction had to be completed within a 10-week window during the 2005 summer break.
After evaluating the situation, MMS Consultants chose an AdvanTex Treatment System, manufactured by Orenco Systems, for its relatively simple, robust, and part-time operation, low energy consumption, and ease of construction. AdvanTex is a textile packed-bed filter that operates in the recirculating mode and is unaffected by variable flows.
Moreover, its low energy consumption and minimal maintenance requirements were an affordable solution.
It took only four weeks to install and commission an AdvanTex Treatment System with four AX100 pods, which easily fit into the allotted space. MMS provided design, permitting, and construction management for the project.
Once the AdvanTex system was installed, the consistently high quality of the effluent took the strain off the existing drainfield, which was rehabilitated and placed back into service. Today, the system's effluent BOD5, TSS, and NH3-N average less than 10 mg/L, 10 mg/L, and 5 mg/L, respectively.