RFI - Attachment F - Engineering Report

             refereed paper                                                                                 stormwater treatment

                                                                                                     Antecedent dry period was not identified as a constraint, due
                                                                                                   to the impervious nature of the catchment and the absence of a
                                                                                                   base flow; however, at least a three-day antecedent dry period
                                                                                                   was preferred. If the storm was deemed to qualify, Stormwater360
                                                                                                   would inform Cairns Water and Waste Laboratory Services
                                                                                                   (Cairns Water, NATA accreditation # 14204) that samples required
                                                                                       VEE NOTCH
                                                                                         WEIR
                                                                                                   collection and analysis. Analysis was performed by Cairns
                                                                                      PRESSURE
                                                                                     TRANSDUCER
                                                                                                   Water and Waste Laboratory Services, ALS Laboratory Group
                                                                                                   – Brisbane (ALS, NATA accreditation # 825). All water quality
                                                  OUTLET PIPE




                                                                                                   parameters for qualifying storms were sent to an independent
 ROAD




                                                                                                   peer reviewer at Queensland University of Technology (QUT),
                                                                                                   ensuring transparency of data. Test methods for water quality
                                                                                                   analysis used for this study are provided in Table 1.
                                 DRAIN




                                                     SAMPLING TUBE

                                                                                                      Gross pollutants were not monitored as part of this
                                                                                                   study, although significant quantities were captured. Previous
                                                                     AUTOSAMPLER
                                                                                                   monitoring by White et al. (2001) demonstrated that the
                                         AUTOSAMPLER
                                                                      FLOW METER
                                                                                                   Enviropod® filter retained all (100%) litter up to an approach
                                                                                                   flow of 100L/sec.
                           NEL
                       CHAN




                                                   PLAN LAYOUT

                                                                                                   Results and Discussion
                                                                                                   The system was installed at the Streets Creek site in March 2006
Figure 3. Schematic of the sampling location.                                                      and remained an active treatment and sampling site for four
                                                                                                   years until being decommissioned in March 2010. Stormwater360
Sampling Procedure and Equipment                                                                   monitored the system from April 2008 to December 2009. During
A graphical representation of the system is shown in Figure 2.                                     this time, the unit was maintained annually, prior to the onset
The direction of flow through the gully pit insert (EnviroPod®)                                    of each dry season. Complete maintenance involved removing
and into the cartridge media filter (StormFilter®) is shown in                                     all sediments and debris from the system, gully pit insert and
sequence from 1 to 4. The gully pit insert is intended to treat                                    replacing the cartridge media. The gully pit insert required
most flows and filter solids above 100 µm while containing                                         additional manual maintenance approximately once per year.
contaminants in a dry state.                                                                          Maintenance frequencies for the study were conducted
                                                                                                   in line with the systems standard operational lifecycle. Due to
  After treatment by the gully pit insert, water is filtered radially
                                                                                                   the nature of the catchment and size, there was an absence of
through the media cartridge (outside to inside). The media
                                                                                                   a base flow or dry weather flows. Potential pollutant leaching
cartridge had a nominal flow rate of 0.95 L/s (at 46 cm head,
                                                                                                   of soluble contaminants was, however, still accounted for;
when the cartridge is primed) and a peak flow rate of ca. 1.3 L/s
                                                                                                   organic debris left within the system was allowed to break
(at maximum 0.88 m head prior to bypass). The ZPGTM media
                                                                                                   down between maintenance periods and permitted to be
used was a proprietary blend containing perlite (50%), granular
                                                                                                   sampled by the effluent sampler during storm events.
activated carbon (GAC, 10%) and zeolite (40%).
                                                                                                      A summary of the principal analytes sampled is contained
   The system samples were collected using automated
                                                                                                   in Table 2.
influent and effluent samplers (Figure 3), collecting continuous
flow and precipitation data and water quality simultaneously.                                      Suspended Solids
The influent sampler was programmed to send an SMS alert
to Stormwater360, via the GSM cellular network, when the                                           ANZECC (2000), DECC (2007) and Fletcher et al. (2004)
                                                                                                   have identified suspended solids as a stressor of aquatic
sampling program was triggered. A dial-up connection was
                                                                                                   ecosystems. In addition, many of the other pollutants, such
then made to each sampler to download data for analysis.
                                                                                                   as metals, hydrocarbons etc, are transported attached to the
 To qualify as a representative sample, the following criteria                                     suspended solids and sediment. The system achieved an SSC
were specified.
                                             Table 2. Summary of results.
I.      Collection of at least three
        simultaneous influent and                                                     Range of             Median        Range of        Median      Mean Removal
                                                                        No. of
        effluent samples per storm;          Analyte                               Influent EMCs       Influent EMC   Effluent EMCs   Effluent EMC      Efficiency
                                                                        events
                                                                                        (mg/L)             (mg/L)          (mg/L)         (mg/L)     (Sum of Loads)
II. Samples must have been
                                             SSC                           6        75 to 4384            1181           8 to 63          20             99%
        collected while the treatment
        system operated within               SSC < 500
                                                                           6         48 to 180             105           8 to 62          20             78%
        design flow rates (not in            micron
        bypass);                             TP                            6       0.08 to 0.19           0.123        0.02 to 0.15      0.055           47%

III. The sampled portion of the              TN                            6         0.6 to 1.5           1.045         0.2 to 0.9       0.615           44%
        storm event must represent                                                                                      0.175 to
                                             TKN                           6         0.6 to 1.2           1.007                          0.515           49%
        at least 60% of the storm                                                                                        0.800
        total flow volume;                   NH3-N                         6       0.05 to 0.15           0.050        0.05 to 0.07      0.050           31%
IV. A minimum of six data sets               TOC                           6          3 to 16               7            3 to 10           5             32%
        must be collected for a full
                                             DOC                           6          3 to 12               7            3 to 11           6             21%
        performance evaluation.

                                                                                                                                       water     SEPTEMBER 2011 3