RFI - Attachment F - Engineering Report

4
Technical Papers


Spearman Rank Order correlation test,         phosphorus, but are ineffective at            aluminium oxide powder is mixed with
positive correlations (P<0.05) were           removing soluble phosphorus. The              clay to form a slurry, which is coated and
determined between influent and effluent      absorptive filtration properties of the       then baked onto the perlite media. In
EMCs for Ortho-P and NH3+. Based              activated alumina media provides further      operational conditions at low cartridge
on the use of the Mann-Whitney Rank           removal mechanisms of total phosphorus        flow rates, the RCFS also has the ability
Sum test, the difference in the median        in stormwater through the synergistic         to physically remove clay particles in
values between the influent and effluent      effects of precipitation, adsorption and      addition to the clay found within the
EMCs is greater than would be expected        filtration (Ma, 2009).                        media from the manufacturing process.
by chance. Therefore, a statistically                                                       Substitution of silica by aluminum in
                                                  These results not only demonstrate
significant difference (P<0.05) was                                                         soil clay particles causes clays to have
                                              that the system was able to provide
observed for TSS, SSC (<2000µm), SSC                                                        a negative charge (Cornell University,
                                              substantial and consistent removal,
(<500µm), TP, PP, TKN, TN, and ON.                                                          2007). Because of this negative charge
                                              given the high solubility of phosphorus
                                                                                            at sites on or within the media structure,
Suspended Solids                              and at low mean influent concentration
                                                                                            we expect that the media would provide
Parameters                                    for the study of 0.22mg/L, but was
                                                                                            some sorptive capacity and affinity for
Under Australian conditions Walker and        able to attenuate TP captured by the
                                                                                            ammonium. The characteristics of the
Wong (1999) found that most suspended         system over the entire course of the
                                                                                            media would also result in an increase in
solids in stormwater runoff is smaller than   study. The soluble fraction appears to
                                                                                            pH. This increase in pH would cause the
500µm. In this study the closest parameter    be higher than found by Vaze and Chew
                                                                                            ammonium to convert to ammonia and
was SSC<500µm. Influent EMCs for SSC          (2004) under Australian conditions;
                                                                                            then volatilise into the atmosphere.
<500µm ranged from 9mg/L to 393mg/L           they estimated that 20 to 30% of the
with a median of 29mg/L and a mean of         phosphorus is soluble. It would be               Fletcher et al. (2004) measured
66mg/L. Corresponding effluent EMCs           expected, given the primary removal           nitrogen concentrations of at least 2mg/L
ranged from 2mg/L to 10mg/L with a            mechanism of the RCFS is physical             for most urban land uses within Australia,
median of 3mg/L and a mean of 4mg/L,          filtration, that a higher particulate         while Duncan (1999) determined
resulting in an ER of 93% and a SOL           fraction of phosphorus would yield            median concentrations for roads and
efficiency of 94%.                            a similar result.                             urban catchments of 2.2 to 2.5mg/L.
                                                                                            In Melbourne, Taylor et al. found that,
   This result needs to be explained             Fletcher et al. (2004) measured mean
                                                                                            for TN in stormwater, 49% consisted of
in context with lower than expected           TP concentrations of between 0.25
                                                                                            dissolved inorganic nitrogen (NH3+ and
influent concentrations. High pollutant       and 0.50mg/L for most land uses while
                                                                                            NOx), which compares well with the 44%
concentrations lead to high percentage        the BMP Database (2010) suggests
                                                                                            dissolved inorganic nitrogen load from
reductions and tend to over-estimate          a typical TP range 0.11 to 0.38mg/L,
                                                                                            the RCFS study. The soluble component
the removal efficiency of pollutants from     across a variety of land uses. Clearly
                                                                                            of nitrogen in stormwater found by
stormwater treatment systems (CSIRO,          the mean influent TP concentration of
                                                                                            Wicks et al. (2011) and Miguntanna et al.
2010). A literature review by Duncan          0.22mg/L for this study correlates well
                                                                                            (2010) from roadways and commercial
(1999) showed that the median influent        with the published data from Australia.
                                                                                            areas in Queensland was 50 to 60%. Vaze
concentration for total suspended             In addition, the removal processes of
                                                                                            and Chew (2004), also under Australian
solids ranged from the lowest 41mg/L          physical straining and adsorption are
                                                                                            conditions, found that the soluble portion
for roofs to 232mg/L for urban roads.         independent of location and solely a
                                                                                            of nitrogen in stormwater can be up to
Fletcher (2004) found that mean influent      function of water chemistry, filtration
                                                                                            50%. In the RCFS study, soluble organic
concentrations for roofs to roadways          media and associated hydraulic
                                                                                            nitrogen was not measured; however,
ranged from 20mg/L to 270mg/L.                conductivity. Hence our results should
                                                                                            assuming a modest allowance for soluble
                                              apply to Australian stormwater.
Phosphorus Parameters                                                                       organic nitrogen the soluble component
                                              Nitrogen Parameters                           of nitrogen in stormwater for the RCFS
Given that the phosphorus removal
                                              Given that the nitrogen removal target in     study would be expected to be similar to
target in the Australian context is based
                                              the Australian context is based solely on     results from Australian studies.
solely on TP load removal efficiency, the
review of additional data was required        TN load removal efficiency, the review of     Conclusions
to further demonstrate the significance       additional data was required to further
                                                                                            Between April 2011 and June 2012, 13
of the RCFS TP removal efficiencies           demonstrate the significance of the
                                                                                            storm events were monitored and were
obtained. In an effort to isolate             RCFS TN removal efficiencies obtained in
                                                                                            determined to meet the relevant USA
phosphorus removal efficiency based on        this study. In an effort to further isolate
                                                                                            storm data collection requirements.
solubility of TP, dissolved phosphorus        nitrogen removal efficiency NH3+ was
                                                                                            Significant reductions in sediment and
was also measured. Removal efficiencies       also measured. Removal efficiencies
                                                                                            nutrient pollutant concentrations were
for TP and dissolved P were 86% and           based on NH3+, led to overall removal
                                                                                            measured between influent and effluent
74%, respectively, using the ER method        efficiency of 63% based on the ER and
                                                                                            sampling locations using the Efficiency
cf 87% and 67%, using the SOL efficiency      60% using the SOL efficiency calculation
                                                                                            Ratio (ER) calculation method (TSS 90%,
calculation method.                           method.
                                                                                            TP 86%, and TN 56%) and Summation
   The removal of dissolved phosphorus           There are several pathways in which        of Load (SOL) efficiency calculation
is unsurprising but warrants further          ammonium reduction may be occurring           method (TSS 91%, TP 87%, and TN 50%).
discussion. Traditional forms of treatment    in the RCFS system that require further       These results demonstrate that the
such as settling and inert filtration         discussion. During the manufacturing          radial cartridge filter system was able
are able to remove particulate bound          process of the activated alumina media,       to successfully meet the current load-




water SEPTEMBER 2014