RFI - Attachment F - Engineering Report

        refereed paper                                                          stormwater treatment

 Table 3. Nitrogen results from Storm 6.
                                                         Influent EMC              Effluent EMC               Mean Removal Efficiency
 Phase                           Analyte
                                                             (mg/L)                    (mg/L)                     (Sum of Loads)
                                   TN                         0.8                         0.4                            50%

 Total                            TKN                         0.8                        0.34                            58%
 (dissolved and                  NH3-N                       0.15                        0.07                            53%
 particulate)                     Org-N                      0.65                        0.27                            58%
                               NO3-/NO2--N                   0.01                        0.06                           -500%
                                   TN                         0.4                         0.3                            25%
                                  TKN                        0.39                        0.23                            41%
 Dissolved                       NH3-N                       0.16                        0.073                           54%
                                  Org-N                      0.23                        0.157                           32%
                               NO3-/NO2--N                   0.01                        0.07                           -600%
                                   TN                         0.4                         0.1                            75%
                                  TKN                        0.41                        0.11                            73%
 Particulate
                                 NH3-N                        0                            0                              N/A
 (by calculation)
                                  Org-N                      0.41                        0.11                            73%
                               NO3-/NO2--N                    0                            0                              N/A

reduction recorded in the Stormwater360          biological uptake or denitrification               Given the removal efficiency for
trial could be related to the difficulty in      (in an anaerobic environment).                  suspended solids, the high removal
removing TP at very low influent EMCs,           Consequently, the consistent removal            of particulate organic nitrogen is
and a much higher removal rate (similar          of TN exhibited by the system deserves          understandable. Removal mechanisms
to the 70% recorded by JCU) could be             further consideration. The majority (ca.        for dissolved organic nitrogen are less
expected as the influent EMC increased.          95%) of the total nitrogen load at Kuranda      obvious. It is possible that there is
                                                 is TKN and a breakdown of TN species            some adsorption to the ‘schmutzdecke’
   The system achieved an aggregate load         is contained in Table 3.
reduction for total nitrogen (TN) of 44%,                                                        (bio-film) that develops on the cartridge;
while the median influent and effluent              A small proportion of this TKN load          another possibility is removal under
EMCs for TN were 1.045 mg/L and 0.615            (ca. 5%) is ammonia nitrogen, which             the anaerobic conditions within the
mg/L respectively (Table 2). Again, this         implies that ca. 90% of the total nitrogen      standing water within the wet-zones,
influent EMC is low with respect to most         load is present as organic nitrogen, in         being the wet-sump and around the
                                                 either soluble or particulate forms. An         base of the cartridge.
of the published data and, according to
                                                 expanded nitrogen suite analysis was
Duncan (1999), it correlates well with the                                                           When runoff first enters the StormFilter®,
                                                 conducted for Storm 6, and filtered (0.45
median for data from forested catchments                                                         it initially displaces the standing water
                                                 micron) and unfiltered samples were
(0.95 mg/L), but is significantly lower than                                                     in the wet-zones. Any pollutants in the
                                                 processed in order to establish whether
the median for roads (2.2 mg/L) or urban                                                         standing water are sampled by the effluent
                                                 the removal processes, for this event,
catchments (2.5 mg/L). Fletcher et al.                                                           sampler (once they have passed through
                                                 involved particulate removal or removal of
(2004) recommends using a typical total          dissolved species. Essentially, the entire      the StormFilter® cartridge), but they are
nitrogen value of at least 2 mg/L for most       TN load was present as TKN and ca. 20%          not sampled by the influent sampler.
land uses, with the exception of forested        of this was ammonia-N (Table 3).                Furthermore, the last of the runoff to
catchments.                                                                                      enter the cartridge during a storm event
                                                    The entire ammonia-N load was
  The total nitrogen results from JCU            soluble, and the treatment train system         does not necessarily pass through the
and SW360 are presented in Figure 6.             achieved 54% removal of this species.           filter cartridge during that event and
The spread of influent EMCs is broad,            The remainder (ca. 80%) of the TN/TKN           may be retained within the wet-sump
but removal efficiency appears relatively        load was present as organic nitrogen, of        until the next storm event, whereupon
consistent and substantial. This is in spite     which ca. 35% was dissolved. Overall,           it is displaced. When the (particulate or
of the low influent concentrations. TN is        73% removal of particulate organic              dissolved) organic nitrogen converts to
generally considered to be predominantly         nitrogen and 32% removal of dissolved           ammonia in the anaerobic wet sump, it can
soluble, which is best removed by                organic nitrogen was achieved.                  be removed as ammonia-N by the zeolite.

 Table 4. Grab samples from wet sump.
                    Antecedent Dry                      Diss. Cu     Diss. Zn      DOC           Diss. N    Diss. NH3-N         Diss. NOx--N
 Date                                      Report #
                     Period (days)                       (mg/L)       (mg/L)      (mg/L)         (mg/L)        (mg/L)              (mg/L)
 07/07/2008                8                  40627      0.011          0.053       17              -              -                 -
 20/02/2009                6                  42998      0.001          0.016        -            2.4            2.39              <0.01
 06/05/2009               19                  43826      0.005          0.082       16            7.2            5.85               0.72
 21/07/2009               79                  44703      0.004          0.083       20            3.4            2.24              0.025


                                                                                                               water    SEPTEMBER 2011 5