Treatment perform treatment syste SUN 1 Funding provided by NYSDEC grant mance of advanced onsite wa ems in the Otsego Lake water 2008-2011 1 Submitted by: Holly Waterfield NY Oneonta Biological Field Station 5838 State Highway 80 Cooperstown, NY 13326 #49298. astewater rshed
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Advanced Onsite Treatment System Performance Final Report … · This report documents the treatment performance of four advanced onsite wastewater treatment systems based on monitoring
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Treatment performance of advanced onsite wastewater
treatment systems in the Otsego Lake w
SUNY Oneonta Biological Field Station
1 Funding provided by NYSDEC grant #49298.
Treatment performance of advanced onsite wastewater
treatment systems in the Otsego Lake watershed
2008-20111
Submitted by:
Holly Waterfield
SUNY Oneonta Biological Field Station
5838 State Highway 80
Cooperstown, NY
13326
Funding provided by NYSDEC grant #49298.
Treatment performance of advanced onsite wastewater
atershed
EXECUTIVE SUMMARY
This report documents the treatment performance of four advanced onsite wastewater
treatment systems based on monitoring during the summers of 2008 through 2011. All four
systems are installed in the Otsego Lake watershed; three were installed as part of a NYS DEC
grant to demonstrate the use of advanced onsite wastewater treatment systems. Three systems
have been monitored since 2008 (Waterfield and Kessler 2009, Waterfield 2010, Waterfield
2011); OWTS 1 and OWTS 2, funded by the grant, and the UIC system (serving BFS Upland
Interpretive Center). Another system, also funded by the grant, was installed in the spring of
2009 at the BFS Thayer Farm; this system serves three buildings; the Hop House, Boat House,
and a rented residence. Many of these enhanced treatment technologies are new the region, and
thus are unfamiliar to industry professionals, regulators, and residents. For this reason, a DEC
grant was sought and obtained to fund a demonstration project to install and monitor the
treatment performance of six shared advanced treatment systems. The scope of the grant has
since been amended, changing the total number of treatment systems to four, with the last
installed in early 2011 to serve SUNY Oneonta’s newly renovated Cooperstown Campus, which
houses the Biological Field Station and the Cooperstown Graduate Program. The grant did not
fund the installation of the system, though the treatment technologies used were chosen by the
demonstration project’s coordinators.
Treatment performance was assessed based on the following analyses: biochemical
oxygen demand (BOD or CBOD), total suspended solids (TSS), nitrate (NO3), ammonium
(NH3), and total phosphorus (TP). Systems were sampled a total of about 31 occasions, though
all four systems weren’t necessarily sampled on each collection date. Detailed analysis of each
system’s performance is provided in the System Performance, Operation, and Maintenance
section of the 2008-2011 report. Overall, treatment systems performed well, but mainly because
they were actively managed and serviced by qualified professionals. The systems incorporating
textile filters received the most consistent use with the incoming effluent being of typical
household strength (higher than the other systems monitored). Outgoing effluent from these units
was of the highest quality, achieved the best nitrogen transformation rates, and was the least
variable of the systems monitored. The aerobic treatment unit (ATU) serving the UIC produced
effluent of consistent quality, though the system saw very low use compared to its designed
capacity. It handled typical UIC functions and events (field trips, workshops, etc.) and long
periods of low use very well without compromising effluent quality. The foam filter’s treatment
was most variable of the four systems and produced effluent of lower quality than the other units.
The configuration and dosing regime of this system may play a role in the variability observed
throughout this monitoring program.
In the end, most treatment performance issues were improved by communicating with the
trained service provider contracted for each system. As the manufacturer’s recommend, regular
maintenance is needed in order for these systems to operate as they are intended and produce
high quality effluent. Homeowners should be encouraged (and potentially regulated) to prioritize
such maintenance as they would for other major investments (heating systems, vehicles, etc.).
Treatment performance of advanced onsite wastewater treatment systems
in the Otsego Lake watershed, 2008-20112
Holly Waterfield3
INTRODUCTION
This report serves to document the treatment performance of four advanced onsite
wastewater treatment systems monitored during the summers of 2008 through 2011. All four
systems are installed in the Otsego Lake watershed; three were installed as part of a NYS DEC
grant to demonstrate the use of advanced onsite wastewater treatment systems. Three systems
have been monitored since 2008 (Waterfield and Kessler 2009, Waterfield 2010, Waterfield
2011); OWTS 1 and OWTS 2, funded by the grant, and the UIC system (serving BFS Upland
Interpretive Center). Another system, also funded by the grant, was installed in the spring of
2009 at the BFS Thayer Farm. This system serves three buildings; the Hop House, Boat House,
and a rented residence. Due to operation and maintenance issues, OWTS 2 was not monitored in
2010 or 2011. Treatment performance was assessed based on the following analyses:
biochemical oxygen demand (BOD or CBOD), total suspended solids (TSS), nitrate (NO3),
ammonium (NH4), and total phosphorus (TP).
Otsego Lake is located in northern Otsego County, New York. According to the
historical overview by Harman, et al. (1997), the monitoring of Otsego Lake’s water quality
dates back to a 1935 NYS Department of Environmental Conservation (DEC) study. Routine
water quality monitoring efforts began subsequent to the establishment of the Biological Field
Station (BFS) in 1968 (Harman, et al. 1997). Comparisons to these and other historical datasets
had shown overall decreasing water quality conditions, noting in particular increased
phosphorous concentrations likely tied to loading from watershed activities (agriculture, road
maintenance, onsite wastewater treatment, etc.). Onsite wastewater treatment (septic) systems
are estimated to contribute only 7% of the total phosphorus load (Albright 1996), though the
combination of the bio-available form and time of greatest loading at the height of the growing
season is likely to lead to stimulation of algal production (Harman, et al. 1997). The cascading
effects of such nutrient loading on the lake’s ecosystem are far-reaching, and began to concern
lake users and the Village of Cooperstown, which uses Otsego Lake as its source of drinking
water. In 1985, the Village implemented public Health Law 1100 in order to give them legal
grounds to protect the lake as their source of drinking water (Harman, et al. 1997). Additional
actions to curb further water quality degradation in the lake culminated in the formation of a
watershed management plan in 1998, which identified nutrient loading as the greatest threat to
the health of Otsego Lake. Wastewater treatment via onsite treatment systems were listed
second on a prioritized list of action areas (Anonymous 1998), and efforts to manage the
effectiveness of these treatment systems began with a 2004 inventory of all systems in the
established Lake Shore Protection District followed by the inception of the inspection program in
2005 (Anonymous 2007). Under the program, any system found to be in failing condition is to
be replaced within one calendar year. Such replacement systems generally make use of
advanced or enhanced treatment technologies due to conditions that constrain the use of
2 Funding provided by NYSDEC grant #49298.
3 Research Support Specialist, SUNY Oneonta Biological Field Station.
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conventional designs, such as setback to the lake or a tributary, soil depth to bedrock or
groundwater, percolation rate, etc. Many of these enhanced treatment technologies are new the
region, and thus are unfamiliar to industry professionals, regulators, and residents. For this
reason, a DEC grant was sought and obtained to fund a demonstration project to install and
monitor the treatment performance of six shared advanced treatment systems. The scope of the
grant has since been amended, changing the total number of treatment systems to three, with the
last installed in December of 2008.
Biochemical oxygen demand (BOD or CBOD) and total suspended solids (TSS) are
typical metrics used to characterize the strength of residential wastewater (Crites and
Tchobanoglous 1998). BOD is an analysis used to determine the relative oxygen requirements
of wastewater, effluents, and polluted waters, by measuring the oxygen utilized during a given
incubation period (APHA 1992). It is expected that organic material is broken down as
wastewater progresses through a treatment system, thus decreasing the oxygen requirements of
highly-treated wastewater and in turn resulting in lower BOD concentrations over the course of
the treatment system (APHA 1992). TSS analysis measures the total amount of suspended or
dissolved solids in wastewater. Solids may negatively affect water quality for drinking or bathing
and potentially clog a drain field. As with BOD, the amount of solids in treated effluent should
be lower than that of raw wastewater (APHA 1992).
Nitrate and ammonia concentrations will provide insight into the physio-chemical
conditions along the treatment train, as the transformations between various nitrogen forms are
dependent on oxygen availability, alkalinity, temperature, and the presence of specific bacterial
populations. Nitrogen is a dynamic component of wastewater treatment systems, which are often
designed to facilitate specific transformations of nitrogen species. Advanced treatment systems
most often incorporate a secondary treatment step that involves aerating the wastewater in order
to create favorable conditions for the bacterial transformation of ammonia to nitrate, called
nitrification. Nitrogen can be completely removed from the waste stream through the process of
denitrification, during which nitrate is converted to nitrogen gas (N2), which is released to the
atmosphere. Nitrification is generally considered the most limiting step of this overall nitrogen
removal process, as it supplies the nitrate that is converted to N2 gas.
Phosphorus, as previously mentioned, is the nutrient of greatest concern with regards to
vulnerable freshwater bodies. The removal of phosphorus from the waste stream prior to
subsurface disposal will be of great benefit to lake management efforts should the technologies
installed prove to be successful. The nutrient removal units installed in all four systems are of the
same, or very similar design, sourced from a single manufacturer. Phosphorus removal occurs
via adsorption of P onto active sites of an iron-oxide based reactive media; this design results in
the gradual reduction in performance as active adsorption sites on the media surface become
occupied. Eventually the adsorption capacity of the media is exhausted and the media must be
replaced in order to restore the treatment unit’s ability to effectively reduce the phosphorus
concentration leaving the treatment system.
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METHODS AND MATERIALS
Four onsite wastewater treatment systems (OWTS) were monitored in this study and are
illustrated and described in Figure 1; these include the systems serving the SUNY Oneonta BFS
Thayer Farm Upland Interpretive Center (UIC) and Hop House (HH) and two shared homeowner
systems, OWTS 1 and 2. The UIC system has relatively high treatment capacity, as the UIC was
built to accommodate large groups for field trips and meetings. However, typical water usage is
relatively low due to the short duration of most events (<4 hours); actual flow has not been
measured. The system was installed and use commenced in fall of 2005. The system has been in
continuous operation, though initially the main tank was not sealed adequately and as a result
proper function did not begin until fall of 2007. Use of this facility increased during the summers
of 2009 and 2010, when typical BFS operations were moved temporarily to the Thayer Farm. A
period of intensive use occurred in 2011 and is reflected in the performance results. OWTS1 and
OWTS2 are located within 100 feet of the western shore of Otsego Lake off of State Highway
80, and are used mainly on weekends during the summer. Each system is shared by two adjacent
residences and they are designed to receive daily flows of 440 gallons and 550 gallons
respectively. Actual flow for OWTS1 was not measured. Flow through OWTS2 was measured
by the service provider. OWTS1 has been in use since 1 June 2006. OWTS2 has been in use
since 1 June 2007; this system was not monitored in 2010 or 2011 due to operational issues,
which have since been resolved. The HH system was installed at the BFS Thayer Farm to serve
the Hop House (BFS temporary main offices and labs), the Thayer Boat House, and the Thayer
Farm House (a residential rental) and operation began in April 2009 with waste from the Hop
House and Farm House. Flow from the Boat House began in August 2009. The system receives
consistent domestic flow from the Farm House, which is anticipated to be beneficial to the
treatment system especially during the winter months, which is a low-occupancy period at the
BFS.
Preliminary sampling efforts were conducted during the summer of 2007 in order to
assess the concentrations of various chemical and nutrient parameters. Regular grab samples
were collected between May and August 2008, and June through September 2009. Weekly
samples were collected between 9 June and 13 August 2010 and 6 June and 3 August 2011.
During each sampling event, approximately 600 mL of wastewater were collected following
each treatment component of all systems. Each sample site is shown in Figure 1 as “S#”.
Samples were tested for BOD5 using methods summarized by Green (2004). This method
involves determining initial dissolved oxygen (DO) concentration of the sample and nutrient
buffer followed by incubation at 20°C for five days and determination of the final DO
concentration. Samples were diluted to obtain target DO values such that the 5-day DO
concentration would be lower than the initial by at least 2 mg/L but with a final concentration
greater than 1 mg/L. These conditions were not always achieved, thus valid BOD values were
not obtained for every sample collected. Because a nitrification inhibitor is used during
incubation, results are presented as values of CBOD, and are associated with the carbonaceous
oxygen demand rather than the total oxygen demand (APHA 1992). Overall CBOD reduction
rates for each secondary treatment unit (OWTS 1, 2 and HH filters, UIC 1-3) were calculated
based on the average CBOD concentrations observed over the monitoring period, presented in
Table 6.
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Figure 1. Onsite wastewater treatment system configurations. “S#” indicates a sampling point.
A) The UIC system is comprised of a 2-compartment tank, a phosphorus removal unit, a pump tank, and gravel bed drainfield.
Wastewater is circulated and aerated in the first chamber (UIC1 and 2), and settles in the clarification chamber for final solids
settling (UIC3). It then flows through the phosphorus removal unit, on to a pump chamber (UIC4), from which it is pumped in to
the drain field.
B) OWTS1 provides primary treatment in a septic tank and processing tank (PTE) which flow into an equalization tank, then to a
pump tank where the wastewater is pumped and sprayed over an open-cell foam media filter (BFE). In this case the foam media
filter aerates the wastewater and provides surface area for beneficial bacteria, increasing organic digestion. 25% of flow is
returned to the headworks of the processing tank to facilitate the removal of nitrogen from the waste stream, and 50% flows to
the P removal unit (PRE) and on to the drainfield via gravity.
C) OWTS2 provides primary treatment in 2 septic tanks which flow to a two-compartment processing tank. Effluent flows from
the processing tank to a pump tank which periodically doses a textile media filter. Filter-effluent (AXE) is split between the
processing tank (PTE) and the P removal unit (PRE). A portion of effluent from the textile media filter is returned to the
processing tank to facilitate the removal of nitrogen from the waste stream.
D) HH provides primary treatment in 2 septic tanks (STE) which flow to a two-compartment processing tank (PTE). Effluent is
pumped from the processing tank to a textile media filter. Filter-effluent (AXE) is split between the processing tank (PTE) and
the P removal unit (PRE). A portion of effluent from the textile media filter is returned to the processing tank to facilitate the
removal of nitrogen from the waste stream.
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Total suspended solids (TSS) concentration was determined according to the standard
method (APHA 1992). A recorded volume of wastewater was filtered through a rinsed, dried,
pre-weighed glass fiber filter. Filters were dried for a minimum of 24 hours at 105°C in a
gravimetric oven and then removed to a desiccator to cool before being weighed. The
concentration of solids in each sample was calculated from the weight of the filtered solids and
the volume of sample filtered; concentrations are reported in mg solids/L. Overall TSS reduction
rates for each secondary treatment unit (OWTS 1, 2 and HH filters, UIC 1-3) were calculated
based on the average TSS concentrations observed over the monitoring period, presented in
Table 6.
Total phosphorus concentrations were determined using the ascorbic acid following
persulfate digestion method run on a Lachat QuikChem FIA+ Water Analyzer (Laio and Marten
2001). Nitrate and ammonia concentrations were also determined for most samples, using
Lachat-approved methods (Pritzlaff 2003, Liao 2001). All reduction and transformation rate
estimates are calculated based on average concentrations observed over the duration of the
monitoring period (Table 6). Total nitrogen concentrations were not determined and are not
presented here due to incomplete oxidation of ammonia to nitrate during the digestion process,
which results in underestimation of TN concentration.
SYSTEM PERFORMANCE, OPERATION, AND MAINTENTANCE
Monitoring results for each sampling location in all treatment systems are presented in
tabular and graphical form for all parameters monitored (Tables 1-6, Figures 2-5). The tables
summarize the testing results for each year (2008-2011) and over the entire monitoring period,
including calculated standard error and the sample size. Figures for CBOD, TSS, TP and
NO3/NH4 include standard error bars. The overall performance of the systems can be assessed by
comparing the first stage of treatment with the last. Typical CBOD concentrations associated
with raw wastewater vary greatly (100 – 600 mg/L) depending on per capita water usage and
inputs of solids to the system (i.e. garbage grinder waste) (Crites and Tchobanoglous 1998). The
industry standard for BOD5 and TSS in effluent from secondary treatment units is 30 mg/L (NSF
2007).
Each system will be discussed individually in the following sections; the treatment
performance of each is assessed in addition to a description of operation and maintenance issues
encountered over the course of the monitoring period. At the time of installation and design,
phosphorus removal units were available from single manufacturer, and so the same treatment
unit is used in all four systems; the results obtained for each treatment system expose the same
performance and maintenance issues for this specific treatment unit, which are addressed in the
last section, Phosphorus Removal Components.
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average +\- SE n average +\- SE n average +\- SE n average +\- SE n average +\- SE n