Metabolic Studio Pilot Wetland Study Report…requiring little energy input, and reducing carbon dioxide (a greenhouse gas). The reported treatment performance and benefits above led

Pilot Wetland Study Treatment Performance Report

Geosyntec Consultants 2017

metabolic studio

Metabolic Studio

1745 N Spring St. #4 Los Angeles, CA 90012

(323) 226-1158

Metabolic Studio Pilot Wetland Study

i Metabolic Studio Pilot Wetland Study

TABLE OF CONTENTS

Page

1. INTRODUCTION ................................................................................................. 1

1.1 Background ............................................................................................. 1 1.2 Water Quality Objective ...................................................................... 2 1.3 Baseline Conditions ................................................................................ 3 1.4 HSSF Wetlands and Design Constraints ............................................ 4 1.5 Study Objectives ..................................................................................... 5

2. TREATMENT PERFORMANCE .......................................................................... 7

2.1 Indicator Bacteria .................................................................................. 7 2.2 Physical and Chemical Water Quality Parameters .................... 10

3. HYDRAULIC RETENTION TIME ....................................................................... 17

4. VEGETATION COVERAGE ............................................................................ 19

5. CAPITAL AND O&M COSTS.......................................................................... 21

5.1 Capital Costs ......................................................................................... 21 5.2 O&M Costs .............................................................................................. 22 5.3 Total Annual Costs ................................................................................ 22

6. CONCLUSIONS ................................................................................................ 24

7. REFERENCES ..................................................................................................... 26

TABLE OF CONTENTS (Continued)

Page

ii Metabolic Studio Pilot Wetland Study

LIST OF TABLES

Table 1 Mean and Theoretical Hydraulic Retention Time ........................ 17

Table 2 Capital costs for one and three three-tank in-series systems ... 22

Table 3 Annual O&M costs for one and three three-tank in-series systems ....................................................................................................... 22

Table 4 Annual operating costs for one and three three-tank in-series systems ............................................................................................ 23

Table 5 Physical and Chemical Water Quality Parameters Measured in the Field ................................................................................................. 29

Table 6 Physical and Chemical Water Quality Parameters Measured in the Laboratory ..................................................................................... 30

Table 7 Water Quality Data of Captured Rainwater Stored in Cisterns Onsite and LAR Water ........................................................... 32


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iii Metabolic Studio Pilot Wetland Study

LIST OF FIGURES

Figure 1 Locations of Bending the River Back into the City, the wetland site, and grab sampling ......................................................... 2

Figure 2 Total coliform geometric mean concentration for samples collected at selected locations ........................................................... 7

Figure 3 Fecal coliform geometric mean concentration for samples collected at selected locations ........................................................... 8

Figure 4 Enterococci geometric mean concentration for samples collected at selected locations ........................................................... 9

Figure 5 Average total suspended solids at selected locations along the treatment systems ........................................................................... 11

Figure 6 Average turbidity at selected locations along the treatment systems ................................................................................... 12

Figure 7 Average conductivity at selected locations along the three treatment systems ................................................................................... 13

Figure 8 Average oxidation reduction potential (ORP) at selected locations along the three wetland systems .................................... 14

Figure 9 Average BOD5 at selected locations along the treatment systems ....................................................................................................... 15

Figure 10 Average nitrate concentration at selected locations along the three wetland systems ................................................................... 16

Figure 11 RWT effluent concentration for the gravel and clay pellet wetlands .................................................................................................... 18

Figure 12 Vegetation coverage of individual wetland cells in the three wetland systems. ..................................................................................... 20

Figure 13 a) Water truck; b) floatable pump .................................................... 33

Figure 14 a) Influent storage 1 at the lower level and fabric filter installation prior to refilling the storage tanks; b) influent storage 2 and the intermediate tank ................................................ 33


Page

iv Metabolic Studio Pilot Wetland Study

Figure 15 The pilot wetland site plan ................................................................... 34

Figure 16 The layout of the wetland plants in each wetland cell. ............. 35

Figure 17 A flow control and recording setup installed at the influent of the clay pellet wetland, C. ............................................................. 35

Figure 19 An effluent sampling port located at the end of each wetland cell .............................................................................................. 36

LIST OF APPENDICES

Appendix 1 – Water Quality Results

Appendix 2 – Rainwater Versus LAR Water Quality

Appendix 3 – Materials and Methodology

Acronyms and Abbreviations

v Metabolic Studio Pilot Wetland Study

BOD5 Five-Day Biochemical Oxygen Demand BRBC Bending the River Back to the City COD Chemical Oxygen Demand CTRS California Toxic Rule Standard DCT Donald C. Tillman Water Reclamation

Plant DTLA Downtown Los Angeles E. coli Escherichia coli HRT Hydraulic Retention Time HSSF Horizontal Subsurface Flow IN Influent LACDPH Los Angeles County Department of Public

Health LAG Water Reclamation Plants LAR Los Angeles River MCL Maximum Contamination Level MPN Most Probably Number NTU Nephelometric Turbidity Units ORP Oxidation Reduction Potential PAHs Polycyclic Aromatic Hydrocarbons PCBs Polychlorinated Biphenyls PSF Pounds Per Square Foot RWT Rhodamine WT TDS Total Dissolved Solids TOC Total Organic Carbon TSS Total Suspended Solids

1 Metabolic Studio Pilot Wetland Study

1. INTRODUCTION

1.1 Background

Water scarcity due to climate change and prolonged droughts in arid regions has fueled a growing interest in capturing and using stormwater and dry-weather runoff for non-potable water applications. These innovative reuse approaches not only help diversify local water resources, but also help municipalities achieve discharge requirements specified in National Pollutant Discharge Elimination System (NPDES) Permits meeting ambient water quality criteria, such as Total Maximum Daily Loads (TMDLs).

The 48-mile long Los Angeles River (LAR) flows through the heart of Downtown Los Angeles (DTLA) discharging into the Pacific Ocean via Queensway Bay in Long Beach. LAR flow in the DTLA area is comprised primarily of 1) Title 22 recycled water discharges from the Los Angeles-Glendale (LAG) and Donald C. Tillman (DCT) Water Reclamation Plants, 2) groundwater underflow from the Glendale Narrows and Arroyo Secotributary (US Army Corps of Engineers, 2013), and 3) overflows from theJapanese Garden, Lake Balboa, Bull Creek, and the Sepulveda BasinWildlife Area (US Army Corps of Engineers, 2012).

Dry-weather base flow in the LAR that exceeds 72 cubic-feet-per-second (cfs) is estimated to be greater than 90% of the time in the DTLA area (Geosyntec Consultants, 2013). Based on a ten-year average discharge of 62 cfs, combined discharges from the LAG and DCT water reclamation plants account for over 80% of total dry-weather flow (Geosyntec Consultants, 2013). Such a unique flow composition makes the LAR water in the DTLA area relatively clean.

The capture of dry-weather runoff from the LAR to provide non-potable water for spray irrigation in nearby public parks was proposed in 2013 (Geosyntec Consultants, 2013) as part of the “Bending the River Back to the City” (BRBC) project – an alternate water use project envisioned by Metabolic Studio (the Studio). The project site is located two miles northeast of DTLA between the 110, 5, and 101 freeways (Figure 1). The proposed project will consist of an inflatable rubber dam within the LAR channel diverting dry-weather flow to a water wheel. The water wheel lifts


the water to a treatment and storage system prior to distribution to nearby parks for spray irrigation. Less than one percent of the diverted flow will be lifted by the water wheel, while the remaining flow will immediately flow back into the LAR through a subsurface flow channel.

Figure 1 Locations of Bending the River Back into the City, the wetland site, and grab sampling

1.2 Water Quality Objective

The Los Angeles County Department of Public Health (LACDPH) sets the water quality objectives for the use of non-potable water sources within the County of Los Angeles, including runoff from the LAR, for aboveground non-potable uses. At the time when BRBC was proposed, Guidelines for Harvesting Rainwater, Stormwater, & Urban Runoff for Outdoor Non-Potable Uses (LACDPH, 2011. “2011 Guidelines”) was the effective guidelines. It stipulated that non-potable water for aboveground outdoor non-potable uses shall meet the following single sample limits for indicator bacteria at the point of use when distributed offsite:

x Total coliforms <10,000 CFU/100mL;

x Fecal coliforms <400 CFU/100mL; and

x Enterococcus <104 CFU/100mL.


It is noted that the above limits are the same as the Marine REC-1 Water Quality Objectives for the Long Beach City Beaches and Los Angeles River Estuary (USEPA Region IX, 2012). In February 2016, the 2011 Guidelines were replaced by “Guidelines for Alternate Water Sources: Indoor and Outdoor Non-Potable Uses (2016 Guidelines, (LACDPH, 2016)) to make the non-potable water use requirements consistent with the California Plumbing Code (LACDPH, 2016). The Tier 3 Standards in the 2016 Guidelines specify that aboveground non-potable water uses shall meet the following water quality objectives:

x NSF 350 Standards or Title 22 Recycled Water Quality equivalenceat the point of use;

x All bacterial limits at point of use when distributed off site;

x California Maximum Contamination Levels (MCLs); and

x The California Toxics Rule Standards (CTRS).

It is noted that the total coliform limit of 2 MPN/100mL referenced in the 2016 Guidelines is intended to benchmark performance and reliability of disinfection. The presence of total coliform is not necessarily associated with fecal contamination. However, with this major change, disinfection is expected to be needed as the final treatment step prior to distribution.

1.3 Baseline Conditions

Dry-weather sampling events were performed between July 2012 and October 2014 to determine concentrations of indicator bacteria and other contaminants in the LAR water (Geosyntec Consultants, 2015). A total of 144 parameters listed in the MCLs, REC 1 and 2, CTRS, and Title 22 were analyzed during the first sampling event. These parameters can be broadly divided into: general chemistry parameters, pesticides, metals, indicator bacteria, nutrients, organic compounds, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs).

Water quality parameters that did not meet the applicable regulatory limits were selected as “priority parameters” and monitored during the subsequent 21 sampling events to provide data necessary for treatment design. These priority parameters were total coliform, fecal coliform, Escherichia coli (E. coli), enterococcus, specific conductance, turbidity,


and pH. The results from the first sampling event concluded that LAR water did not have exceedance concerning pesticides, metals, organic compounds, PCBs, and PAHs.

1.4 HSSF Wetlands and Design Constraints

Horizontal subsurface flow (HSSF) wetlands have been used for a wide range of water treatment applications including: nitrogen and phosphate removal (Tanaka, N., Karunarathna, A.K. & Jindasa, K.B.S.N., 2008), graywater treatment (Dallas, S. & Ho, G., 2005), highway runoff treatment (Terzakis, S. et al, 2008), heavy metal removal from acid mine drainage (Sheoran, A. & Sheoran, V., 2006), and stormwater runoff treatment (Idris, S.M. et al, 2012). It has been reported that 99% or greater indicatorbacteria reduction is achievable using HSSF wetlands (Kadlec, R.H. &Wallace, S.D., 2009).

HSSF wetlands are considered as an attractive alternative to other physio-chemical and biological treatment options. In addition to proven water quality treatment performance, HSSF wetlands bring added benefits of greening highly developed urban spaces, creating wildlife habitats, requiring little energy input, and reducing carbon dioxide (a greenhouse gas).

The reported treatment performance and benefits above led the Studio to consider the use of this treatment option to treat LAR water at the BRBC facilities in early 2014. In a memo prepared by Geosyntec (2014), a conventional full-scale rectangular HSSF wetland with two 5.5 ft. deep gravel beds would occupy a footprint of 65,000 square foot. Such a large footprint was deemed impractical due to the space constraint.

To save space, the Studio subsequently expressed a preference of installing part of the wetland on top of the Studio’s main building roof. To accommodate this siting preference, the wetland systems would be required to meet a loading limit of no more than 150 pounds per square feet (psf). Also, the shape of the roof selected had a five-sided polygon (See Figure 1), this would mean that a wetland with a flexible configuration would be desirable to optimize the use of available space. Given these constraints, alternative media with lower density than conventional gravel media and smaller and shallower beds would need to be considered.


Also, the Studio expressed a preference for using media from sustainable sources.

In order to demonstrate the feasibility of using a wetland system that would meet the above criteria, a pilot study was subsequently planned. During the design phase, a total of 15 alternative media were considered, including: commercial media products (e.g., Growth Rock, Rockwool, expanded clay pellets), natural rock minerals (e.g., perlite, pumice, gravel), and agricultural waste (e.g., wood chips, rice hull, coconut coir).

Three media types, namely gravel, coconut coir, and clay pellets, were ultimately selected. Gravel was selected because of its frequent use as wetland media and was recommended in preliminary design proposed by Geosyntec (2014). Coconut coir was selected as a sustainable and low density alternative that has been used for HSSF wetlands (Tanaka, N., Karunarathna, A.K. & Jindasa, K.B.S.N., 2008). Expanded clay pellets were selected as an alternative because its density was between gravel and coconut coir, and they are typically used as a soil substitute in hydroponic systems. Also, clay was selected by the Studio because they had experimented their use in other projects.

To accommodate the size and geometry of potential spaces available for conducting the pilot study, multiple wetland bed configurations using temporary structures were considered, including high aspect ratio (up to 1:20) rectangular beds with sloped bottoms, elongated rectangular beds that spiraled down from the top of a circular mount, multiple wetland beds in-series. Multiple-bed-in-series using rectangular fiberglass tanks were selected in the end. This option would allow the Studio to construct the systems using their existing contractor, accommodate the space limitations at the site, and allow reuse of materials after the pilot study is complete.

1.5 Study Objectives

To evaluate the performance of HSSF wetland systems for treatment of dry-weather LAR water, a pilot study (study) was conducted. Three HSSF wetland treatment systems were designed and built between June and September 2015. The primary objectives of this study were:


1. To demonstrate that HSSF wetlands were capable of treating LARwater to meet 2011 Guidelines for aboveground non-potable wateruses;

2. To evaluate and compare the treatment performance of threedifferent media types with respect to FIB, turbidity, organics, andnutrient removal; and

3. To determine the hydraulic retention time (HRT) required to achieveoptimal treatment performance.

Findings from this study will provide the design basis for scale-up. They will support the use of HSSF wetland systems for treatment of dry-weather runoff from the LAR and other rivers in similar urban regions for non-potable water use. These results will also provide data to support the use of wetland systems for treatment of dry-weather runoff for bacteria TMDL Marine REC-1 compliance purposes.

The organization of this report is as follows:

Section 2: Treatment Performance

Section 3: Hydraulic Retention Time

Section 4: Capital and O&M Costs

Section 5: Vegetation Coverage

Section 6: Conclusions.


2. TREATMENT PERFORMANCE

2.1 Indicator Bacteria

Indicator bacteria are the primary biological contaminant of concern in LAR water in the previous water quality sampling and testing effort as described in Section 1.3. As such, indicator bacteria in water samples collected from the LAR, the influent to the wetland systems (IN), and the effluent of wetland cells 1, 2, 3, 5, 8, and 9, were analyzed. The total coliform, fecal coliform, and enterococcus results for these locations are presented in Figures 2-4, respectively.

Note: Error bars represent the standard deviation of the geometric mean of n= 4- 8 samples. Figure 2 Total coliform geometric mean concentration for samples collected at selected locations

As shown in Figures 2-4, indicator bacteria concentrations in the LAR water were variable. Although the geometric mean was below the limits specified in the 2011 Guidelines and the bacteria TMDL Marine REC-1, their single sample concentrations did not consistently meet these two


requirements. For example, total coliform concentrations in the LAR water samples were measured in the range between 2 and 16,000 MPN/100mL during the four sampling events performed and one of them exceeded the 10,000 MPN/100mL limit.

Note: Error bars represent the standard deviation of the geometric mean for n=4-8 samples. Figure 3 Fecal coliform geometric mean concentration for samples collected at selected locations

This results showed that total coliform and fecal coliform concentrations in IN (i.e. wetland influent after storage) were 93% and 87% lower than the LAR, respectively (Figures 2-3). This suggests that storage of LAR water prior to treatment provide reductions, although such reductions were not statically significant based on a t-test (p-value=0.16>0.05 for total coliform; p-value=0.24>0.05 for fecal coliform). In contrast, a decrease inenterococcus concentration was not observed after storage. Thisobservation is consistent with other studies where enterococci have beenshown to be more persistent in aquatic environments compared to


coliform bacteria (Davies, C.M. et al, 1995;Anderson, K.L., Whitlock, J.E. & Harwood, V.J., 2005).

Note: Error bars represent the standard deviation of the geometric mean for n=4-8 samples. Figure 4 Enterococci geometric mean concentration for samples collected at selected locations

Reduction in total coliform, fecal coliform, and enterococcus concentrations after one wetland cell treatment was observed. The percentage reduction ranges were 80-92% (effluent geomean = 3.6 - 10.5 MPN/100mL), 60-70% (effluent geomean = 1-1.3 MPN/100mL), and 88-97% (effluent geomean = 1.2-4 MPN/100mL) for total coliform, fecal coliform, and enterococci, respectively. However, these reductions were not considered to be significant according to a t-test (p-value=0.16 for total coliform>0.05, p-value=0.24 for fecal coliform >0.05). The t-test results could have been a result of relatively low IN concentrations, the variability in the data, and the limited number of samples taken.


The effect of providing additional treatment (i.e. with longer HRT) after the first wetland cell with respect to indicator bacteria removal was evaluated. The data suggest that additional treatment provide little to no observable bacterial removal benefits for all the three systems. For the coconut coir wetland, indicator bacteria removal was observed to be optimal after one cell. For the gravel and clay pellet wetlands, adding two more wetland cells was shown to provide negligible improvement. It is worth pointing out that the treatment system was unable to consistently attain an effluent total coliform concentration of at or below 2 MPN/100mL (i.e. the 2016 Guidelines requirements) during the sampling period. This is not surprising because total coliform is an environmental indicator and can be found in surface water and soil. Nevertheless, to attain the prescribed effluent quality consistency for compliance, disinfection of effluent after treatment is necessary.

2.2 Physical and Chemical Water Quality Parameters

pH, turbidity, and conductivity were identified as the primary physical and chemical water quality parameters of concern in the 2015 Report (Geosyntec Consultants, 2015). These three parameters, in addition to others listed in Tables 1-2, were characterized through field measurements and laboratory analysis of grab samples. The results are summarized in Tables 1-2. LAR water and IN had an average pH of 7.7±1.2 and 7.9 ±0.3, respectively. The wetland processes buffered the pH to near neutral, ranging between 6.8±0.1 and 7.0±0.2. These results were consistent with those reported by other researchers (Kadlec, R.H. & Wallace, S.D., 2009).

Total suspended solids (TSS) and turbidity (a surrogate for TSS) were measured at the selected locations and the results at these locations are presented in Figures 5-6, respectively. LAR water contained an average TSS and turbidity of 18 mg/L and 3 NTU, respectively. Both exceeded the limits of 10 mg/L TSS and 2 NTU turbidity as stipulated in 2016 Guidelines (Figure 5). Storage was shown to provide as much as 90% TSS reduction on average, resulting in an average IN TSS of 1.8 mg/L. All effluent TSS levels were consistently well-below the 10mg/L TSS. Consistent with the TSS results, storage provided an average of 80% of turbidity reduction, resulting in an average IN turbidity of 0.6±0.1 NTU, below the 2 NTU limit (Figure 6). The reduction was described as significant per a t-test (p-value=0.04<0.05).


Recognizing the relatively low average IN TSS and turbidity levels, any additional reduction gained through wetland treatment was expected to be limited. Both gravel and coconut wetlands were shown to have further reduced TSS levels consistently to below the detection limit of 0.5 mg/L. It is noted that detectable levels of TSS were measured in all clay pellet wetland effluent samples. These average values were maintained at no more than the average IN TSS level of 1.8 mg/L, thus these were still considered as low.

Note: Error bars represent the standard deviation of n=4 samples. Figure 5 Average total suspended solids at selected locations along the treatment systems

As for turbidity, both gravel and clay pellet wetlands maintained an average of no more than the IN turbidity of 0.6 NTU. Based on the slight turbidity increase detected in Cell 2 of the clay pellet wetland and coupled with the detectable TSS levels in effluent samples in the clay pellet wetland, the gravel wetland provided more consistent turbidity and TSS removal in comparison.

It is noted that effluent turbidity levels in other coconut wetland effluent samples (Cells 2, 3, 5, 8, and 9) rose with the increasing number of wetland cells (i.e. HRT, see Figure 6). The causes had yet to be investigated, but media leaching was thought to be one of the main potential causes. Even


though the average turbidity levels were below the 2 NTU requirements for all effluent samples, the coconut coir wetland was considered to have the poorest turbidity removal performance compared to the other two wetlands.

Note: Error bars represent the standard deviation of n= 4-12 samples. Figure 6 Average turbidity at selected locations along the treatment systems

Conductivity, a surrogate for measuring total dissolved solids (TDS), was another contaminant of concern identified in a previous study (see Section 1.3). High conductivity can be detrimental to plant health and thus it is prudent to maintain the conductivity level at a reasonable level based on the end use. The results show that the average LAR conductivity level was 1,061 µS/cm, above the recommended MCL of 900 µS/cm but below maximum MCL of 1,600 µS/cm (Figure 7) as specified in the 2016 Guidelines. Slight elevated average IN conductivity (1,122 µS/cm) could have been a result of evaporation during storage.

Measurable changes in effluent conductivity was observed after the wetland treatment processes. As shown in Figure 7, conductivity levels in the gravel and clay pellet wetlands generally followed a similar upward trend and increased with HRT (cell 9, gravel = 1,312 µS/cm and clay pellet = 1,256 µS/cm). Conductivity in the coconut coir wetland effluent


decreased with increasing HRT (cell 9 = 968 µS/cm). This striking difference between the gravel and clay pellet wetlands (using inorganic siliceous minerals) and the coconut coir wetland (using organic cellulose materials) is hypothesized to be stemmed from the biochemical environments in these media as supported by the oxidation-reduction potential (ORP) data.

Note: Error bars represent the standard deviation of n=8 samples. MCL = CA Secondary Maximum Contaminant Levels. Figure 7 Average conductivity at selected locations along the three treatment systems

The ORP data (Figure 8) showed that the ORP levels in the coconut coir wetland were much lower than the other two wetlands with an average of -280 mV were measured at the selected locations. The average effluent ORP for the gravel and clay pellet wetlands were +16 mV and +41 mV, respectively. These results suggest that the biochemical conditions in the coconut coir wetland was highly reduced; while the other two were slightly oxidized. A reduced environment favors anaerobic processes, such as metal precipitation, fermentation, and sulfate reduction. The decrease in conductivity, increase in organics (total organic carbon (TOC), chemical oxygen demand (COD), and five-day biochemical


oxygen demand (BOD5)), and reduction in sulfate (see Table 1) with increase in hydraulic retention time suggest these processes took place in the coconut coir wetlands.

Note: Error bars represent the standard deviation of n=8 samples. Figure 8 Average oxidation reduction potential (ORP) at selected locations along the three wetland systems

Consistent with the difference in the ORP results, similar water quality changes were not observed in the gravel and clay pellet wetlands. For example, these two wetlands were shown to provide organics reduction (TOC, COD, and BOD), while no conductivity reduction was observed. Elevated effluent conductivity compared to IN, which could be a result of water loss due to evapotranspiration (Kadlec, R.H. & Wallace, S.D., 2009).

Biodegradable organic concentrations in the LAR and other selected locations were measured. The average BOD5 levels for LAR and IN were 2.8 mg/L and 1.8 mg/L, respectively, well below limit of 10 mg/L as specified in the 2016 Guidelines (Figure 9). This shows that storage provided slight BOD5 reduction. After treatment using two wetland cells, BOD5 concentrations in both gravel and clay pellet wetlands were


reduced to below detection limit of 1 mg/L and remained at the same level after water passed through additional seven wetland cells.

As noted previously, BOD5 concentrations in the coconut wetland were evaluated with measurements collected from cells 8 and 9 exceeding 10 mg/L. This gave an overall increase of 88% BOD5 at cell 9 compared to IN (Figure 9). Consistent with the BOD5 results, an ascending trend was also observed in COD and TOC results. These BOD5 observations suggest that controlling the HRT in the coconut coir wetland would be crucial to limit organic increases and long HRT should be avoided.

Note: Error bars represent the standard deviation of n=4 samples. Figure 9 Average BOD5 at selected locations along the treatment systems

Change in nitrate concentrations was observed in this study. LAR water contained an average nitrate concentration of 4 mg/L as N which was below the Secondary MCL limits as specified in the 2016 Guidelines. Storage did not provide reduction benefits. After two cells of wetland treatment, 99% of nitrate was removed and the concentration remained unchanged in increasing in hydraulic retention time as expected (Figure 10).


Note: Error bars represent the standard deviation of n=4 samples. MCL = California Maximum Contaminant Levels. Figure 10 Average nitrate concentration at selected locations along the three wetland systems


3. HYDRAULIC RETENTION TIME

The HRT of each treatment system was determined theoretically (void space divided by flow rate) and empirically (using rhodamine WT (RWT) dye tracer) (Table 3). The influent flow rate of each treatment system was set to approximately 0.5 liter per minute (lpm) to attain a theoretical HRT of one day per cell. The empirical HRT was calculated based on the time required for the RWT dye to exit the cells.

When calculating the HRT, a RWT mass recovery of at least 80% must be attained (Headley, T.R. & Kadlec, R.H., 2007). As shown in Table 3, tracer test results from gravel and clay pellet wetlands met such a requirement. The RWT masses recovered from these two wetlands were greater than 100%, which could be attributed to evaporation and/or instrumentation errors (e.g. RWT sensors and flow meters). For the coconut coir wetland, only 12% of RWT mass was recovered, and thus an empirical HRT for a typical coconut coir cell could not be determined. The low tracer recovery could be due to the sorption of RWT onto the organic coconut coir media (Lin, A.Y.-C. et al, 2003).

Table 1 Mean and Theoretical Hydraulic Retention Time

Tracer Tests Theoretical HRT, day per

cell Measured Mean HRT,

day per cell

Tracer Volume, mL

Dye Recovery

Initial Dye Detection,

hr

Gravel 1.85 1 123% 13.10 0.80

Coconut coir

Cannot Be Determined

4 12% 0.83 1.08

Clay Pellet

1.66 2 112% 6.77 0.93

The normalized effluent RWT concentrations from cell 1 of the gravel and clay pellet wetlands are shown in Figure 11. The flow of the RWT in these two cells can be described as dispersed based on the shape of the curves. Multiple peaks observed in both wetlands suggest the presence


of multiple flow paths (Levenspiel, O., 1999). This observation is consistent with the design of the wetland where multiple holes were predrilled into the PVC pipes placed horizontally across the wetland bed.

Figure 11 RWT effluent concentration for the gravel and clay pellet wetlands

The calculated HRTs for the gravel and the clay pellet cells were 1.85 and 1.66 days per cell, respectively. They were longer than the theoretical hydraulic retention time of approximately one day per cell. The longer than expected HRTs could be attributed to the presence of extensive plant roots in the wetland cells that were not accounted for calculating the theoretical HRT. Extensive root systems alter flow paths and may create stagnant zones to impede flow (Kadlec, R.H. & Wallace, S.D., 2009).

Regarding the tracer test performed at the coconut coir cell, a relatively short RWT detection time of 50 minutes was recorded. This could be a result of a combination of high hydraulic conductivity of coconut coir (Abad, M. et al, 2005) and the presence of short circuiting in the cell (Levenspiel,O., 1999). Despite the relatively short HRT, treatment performance of thecoconut coir wetland for indicator bacteria and nitrate removal did notseem to be affected and the effluent concentrations were comparableto the gravel and clay systems (see Section 2).


4. VEGETATION COVERAGE

Plant species selected and planting layout were identical in all the wetland cells. After one year of operation, vegetation coverage and size in all the cells are shown in Figure 12. Vegetation coverage and size variation in the gravel and clay pellet wetlands were similar with the first cells having the largest plant sizes and densest vegetation coverage; while the thinnest coverage and smallest plants were found in the last cells (A9 and C9). Such a decrease in plant size and coverage could have been a result of geochemical composition variation in the water, but further analysis would need to be conducted to confirm this.

Vegetation coverage and size change in the coconut coir wetland system was noticeably different from the other two wetland systems. The vegetation coverage, size, and coloration changed abruptly in the mid-section of cell 1. The plant size remained relatively small with little to no noticeable difference from cells 2 to 9. The small plant size in the coconut wetland cells could be related to the presence of highly reduced conditions (i.e. highly negative ORP). It has been reported that such conditions cause oxygen stress in plants, affecting photosynthetic activities and plant growth (DeLaune, R., Pezeshki, S. & Pardue, J., 1990;Bandyopadhyay, B. et al, 1993). Based on the above observations, using a relatively short HRT would be crucial for maintain plant health, in addition to controlling effluent organic concentrations (Section 2.2).

20 Metabolic Studio Pilot W

etland Study

Figure 12 Vegetation coverage of individual w

etland cells in the three wetland system

s.

It is noted that water flow

from left (influent) to right (effluent). T

he white arrow

mark the locations w

here untreated water flow

s into the wetland system

s, while the blue arrow

s mark effluent discharge points.

c)Clay Pellet W

etland

b)Coconut C

oir Wetland

a)Gravel W

etland

C1

C2

C3

C4

C5

C6

C7

C8

C9

B1

B2

B3

B4

B5

B6

B7

B8

B9

A1

A2

A3

A4

A5

A6

A7

A8

A9


5. CAPITAL AND O&M COSTS

The annual capital and O&M costs for deploying these wetland systems were estimated using the material and O&M costs incurred during the study. Based on the findings presented in Section 2-3, it was determined that treatment systems consisting of three cells would be required to provide sufficient redundancy for both the gravel and clay pellet media. The option to use coconut coir as a soil medium was excluded due to its limitation. The BRBC project would provide the water diversion system and effluent storage at the Studio site, costs for water delivery and storage were therefore excluded from the cost estimates presented in this section.

5.1 Capital Costs

The capital costs for a single wetland cell and a single treatment system were estimated for the gravel and clay pellet systems for comparison. The costs of a single cell were assumed to be comprised of a fiber glass tank, metal frames for creating an elevation difference between tanks, plumbing for influent flow distribution and effluent; wetland vegetation, media; and labor costs for assembly. The costs of a treatment system include plumbing for influent distribution, effluent collection, and connections among the wetland cells; pumps for water transfer and flow distribution; and labor for system installation.

System assembly and installation were assumed to be conducted by a contractor who would provide all field equipment, and thus equipment rental was not necessary. The labor rate of $90 per hour per person was assumed. It was assumed that a total of 90 hours of labor would be sufficient to assemble a single wetland cell. An additional four hours of labor effort was required for installation of pumps and other plumbing work. A total of 61 hours of labor would be needed to install a system (i.e. one wetland system with three cells). For three systems connected in parallel with a single inflow, it was assumed that a total of 175 hours of labor would be required. A 15% contingency was also assumed. Table 4 summarizes the total capital costs for installing one and three three-tank in-series systems.


Table 2 Capital costs for one and three three-tank in-series systems

Media Total capital Costs, $/system

One System (up to three wetland cells)

Gravel $17,000

Clay Pellet $19,000

Three Systems (up to three wetland cells per system)

Gravel $44,000

Clay Pellet $50,500

5.2 O&M Costs

O&M activities for treatment wetlands typically involve pretreatment maintenance (e.g., screen filter replacement), pump maintenance, vegetation trimming, pest control, and routine site walks to ensure that the treatment system is in good working order. During the study period, algal fouling in the plumbing system was observed due to the abrupt change in LAR water quality. As a result, additional cleaning was conducted to prevent clogging. Also, it was assumed that sweeping would be required to maintain site cleanliness. Based on the above, approximately 55 hours of labor per annum were assumed to be necessary to perform these activities. The O&M cost estimates for one and three three-tank in-series systems are presented in Table 5. These cost estimates are expressed in terms of annual costs.

Table 3 Annual O&M costs for one and three three-tank in-series systems

Labor Effort, hours/year

O&M by Onsite Staff, $/year

O&M by Contractor, $/year

One System 88 4,080 4,960

Three Systems 154 7,200 8,740

5.3 Total Annual Costs

The total annual cost to provide a wetland system (gravel or clay pellets) is presented in Table 6. To calculate the annual operating costs, a useful lifetime of 15 years for each system and a salvage value of zero at the end of its lifetime with a uniform rate of depreciation were assumed. The results


show that some economy of scale could be achieved if more systems were installed. Also, additional cost saving could be provided by retaining onsite personnel to perform the O&M work.

Table 4 Annual operating costs for one and three three-tank in-series systems

Media O&M by Onsite Staff, $/year

O&M by Contractor, $/year

One System (up to three wetland cells)

Gravel $5,200 $7,900

Clay Pellet $5,400 $8,300

Three Systems (up to three wetland cells per system)

Gravel $8,300 $11,700

Clay Pellet $8,500 $12,100


6. CONCLUSIONS

A pilot study was conducted to evaluate the treatment performance of modular and compact horizontal subsurface flow (HSSF) wetlands for treatment of Los Angeles River (LAR) dry-weather runoff for aboveground non-potable uses. Three systems, each with different media types (gravel, coconut coir, and clay pellets), were tested. Water quality analysis revealed that LAR water contained levels of indicator bacteria exceeding both the LACDPH 2011 and 2016 Guidelines for aboveground non-potable uses. LAR water contained TSS and turbidity levels that exceeded the 2016 Guidelines. Storage of water prior to treatment was shown to reduce total and fecal coliform, turbidity, TSS, and organics. Turbidity and TSS were reduced to below the limits specified in the 2016 Guidelines. Storage, however, did not reduce other contaminants, such as enterococcus, nitrate, and TDS.

These wetlands reduced and maintained indicator bacteria concentrations to levels that complied with the 2011 Guidelines requirements without the use of disinfection. Indicator bacteria concentrations in effluent had an average of 10 MPN/100mL or lower after one cell of treatment and it was maintained at approximately the same levels throughout the treatment processes1. Under the more stringent 2016 Guidelines, disinfection would need to be used to ensure that water quality objectives for bacteria were consistently met. However, the wetland systems were effective in reducing organics (e.g. BOD5 and COD) and nitrate. Based on the water quality results and adding redundancy to the system, it was determined that three cells per system should be used in future designs.

Gravel, coconut coir, and clay pellets have different physical characteristics. Of these three, coconut coir has the lowest density which makes it a better material for rooftop installation where the weight of the system is of a concern. However, coconut coir may cause issues including fine material leaching, dissolved organic concentration increases and odor when inappropriate HRT is used. On the other hand, gravel has the highest density which makes it a less desirable material for rooftop

1Bacteria concentrations can fluctuate across a broad range (2MPN/100mL->10,000MPN/100mL), thus the increases were considered as small from <10 MPN/100mL to <20 MPN/100mL


installation. However, it is the preferred HSSF media compared to clay pellets due to its lower material cost, easy access, higher material integrity, and lack of buoyancy.

This study demonstrated that influent storage of LAR water coupled with a HSSF wetland could be an effective option for the BRBC project. This wetland design approach can be easily integrated into commercial, industrial, and residential properties that have stormwater capture capability to provide alternative water supply for onsite non-potable uses. Additionally, other larger-scale stormwater capture projects for non-potable uses during dry weather could also benefit from the treatment approach evaluated in this pilot study. Further investigation should be performed to determine the use of this treatment approach beyond LAR dry-weather flow in urban areas. These capture, treatment, and use activities can help diversify local water sources and foster greater water sustainability.


7. REFERENCES

Abad, M., et al, 2005. Physical properties of various coconut coir dusts compared to peat. HortScience, 40:7:2138.

Anderson, K.L., Whitlock, J.E. & Harwood, V.J., 2005. Persistence and Differential Survival of Fecal Indicator Bacteria in Subtropical Waters and Sediments. Applied and Environmental Microbiology, 71:6:3041.

Bandyopadhyay, B., et al, 1993. Influence of soil oxidation-reduction potential and salinity on nutrition, N-15 uptake, and growth of Spartina patens. Wetlands, 13:1:10.

Dallas, S. & Ho, G., 2005. Subsurface flow reedbeds using alternative media for the treatment of domestic greywater in Monteverde, Costa Rica, Central America. Water Science and Technology, 51:10:119.

Davies, C.M., et al, 1995. Survival of fecal microorganisms in marine and freshwater sediments. Applied and Environmental Microbiology, 61:5:1888.

DeLaune, R., Pezeshki, S. & Pardue, J., 1990. An oxidation-reduction buffer for evaluating the physiological response of plants to root oxygen stress. Environmental and Experimental Botany, 30:2:243.

Geosyntec Consultants, 2013. LA River Water Reuse Opportunities/Requirements – Irrigation, Los Angeles.

Geosyntec Consultants, 2015. Bending the River Back into the City Project Water Quality Data Summary Los Angeles, CA

Headley, T.R. & Kadlec, R.H., 2007. Conducting hydraulic tracer studies of constructed wetlands: a practical guide. Ecohydrology & hydrobiology, 7:3:269.

Idris, S.M., et al, 2012. Performance of the giant reed (Arundo donax) in experimental wetlands receiving variable loads of industrial stormwater. Water, Air, & Soil Pollution, 223:2:549.

Kadlec, R.H. & Wallace, S.D., 2009 (2nd). Treatment wetlands. CRC Press, Boca Raton, FL.

LACDPH, 2016. Guidelines for Alternate Water Sources: Indoor and Outdoor Non-Potable Uses.

Levenspiel, O., 1999. Chemical reaction engineering. Industrial & engineering chemistry research, 38:11:4140.

Lin, A.Y.-C., et al, 2003. Comparison of rhodamine WT and bromide in the determination of hydraulic characteristics of constructed wetlands. Ecological Engineering, 20:1:75.

McMillan, 2016. Model S-111/S-112/S-114 Liquid Flow Meters. <http://www.mcmflow.com/shop/index.php/model-s-111-s-114.html#prettyPhoto>, September 1.


Sheoran, A. & Sheoran, V., 2006. Heavy metal removal mechanism of acid mine drainage in wetlands: a critical review. Minerals engineering, 19:2:105.

Tanaka, N., Karunarathna, A.K. & Jindasa, K.B.S.N., 2008. Effect of coconut coir-pith supplement on nitrogen and phosphate removal in subsurface flow wetland microcosms. Chemistry and Ecology, 24:1:15.

Terzakis, S., et al, 2008. Constructed wetlands treating highway runoff in the central Mediterranean region. Chemosphere, 72:2:141.

US Army Corps of Engineers, 2012. Donald C. Tillman Water Reclamation Plant Multi-Use Facility Project Sepulveda Dam Basin - Notice of Preparatin Los Angeles County

US Army Corps of Engineers, 2013. Los Angeles River Ecosystem Restoration Integrated Feasibility Report, Los Angeles County

USEPA Region IX, 2012. Long Beach City Beaches and Los Angeles River Estuary Total Maximum Daily Loads for Indicator Bacteria.


APPENDICES


etland Study

APPEN

DIX 1- WA

TER QUA

LITY RESULTS

Table 5 Physical and Chem

ical Water Q

uality Parameters M

easured in the Field

Location W

ater Q

uality O

bjective

LAR

IN

Gravel

Coconut C

oir C

lay Pellets Effluent

Tank

A1

A2

A3

A5

A8

A9

B1 B2

B3 B5

B8 B9

C1

C2

C3

C5

C8

C9

pH

6-8

7.7±1.2 7.9±0.3

7±0.2 6.9±0.2

6.9±0.2 7±0.2

6.9±0.3 6.9±0.4

6.9±0.3 6.8±0.1

6.8±0.1 6.8±0.1

6.9±0.1 6.8±0.1

6.9±0.1 6.8±0.1

6.9±0.1 6.9±0.1

6.9±0.1 6.9±0.3

7.5±0.1

ORP

1, mV

N

A

158 ±115

-31±825±150

20±168 24±190

28±208 6±210

10±227 -274±23

-294±26

-295±24

-304±27

-285±25

-232±51

42±123 15±121

50±134 63±144

48±154 28±156

-21±108

DO

2, mg

/L 9.8±0.5

6.3±1.2 0.7±0.3

0.8±0.2 1.5±0.5

1.8±0.3 1.5±1

1.9±1.4 0.4±0.3

0.3±0.1 0.4±0.1

0.3±0.1 0.4±0.1

0.6±0.1 0.9±0.3

1±0.4 1.2±0.3

1.7±0.4 1.9±0.6

1.6±0.3 7.3±0.2

Co

nduc

t-ivity, µS/c

m

1,600 1061 ±37

1122 ±43

1096 ±60

1151 ±72

1212 ±75

1291 ±111

1300 ±146

1312 ±137

1069 ±63

1067 ±74

1078 ±76

1021 ±103

980 ±52

968 ±41

1102 ±60

1145 ±81

1186 ±109

1260 ±158

1243 ±164

1256 ±160

1320 ±98

Turbid

ity, N

TU3

2 2.9±0.8

0.6±0.1 0.5±0.5

0.3±0.1 0.4±0.3

0.2±0.1 0.2±0.1

0.2±0.1 0.6±0.1

0.9±0.3 1.2±0.3

1.4±0.4 1.3±0.2

1.8±0.2 0.3±0.1

0.7±0.9 0.3±0.1

0.2±0 0.3±0.2

0.3±0.2 0.3±0.1

1Oxid

atio

n-red

uctio

n po

tentia

l. 2Disso

lved

oxyg

en. 3N

ep

hlom

etric

Turbid

ity Unit. Re

d fo

nts indic

ate

exce

ed

anc

e o

f reg

ulato

ry limits. The

numb

er o

f me

asure

me

nts take

n is n=6


etland Study

Table 6 Physical and Chem

ical Water Q

uality Parameters M

easured in the Laboratory

Criteria

Gravel

Coconut C

oir C

lay Pellet W

ater Quality

Parameters

MC

L* LA

R Influent

A2

A8

A9

B2 B8

B9 C

2 C

8 C

9 TO

C1, m

g/L

NA

10.9±9.5

6.6±0.5 5.1±0.1

4.2±0.3 4.5±0.6

6.6±0.6 12.5±1.3

16±3.5 5.1±0.5

4±0.1 4±0.3

BOD

52, m

g/L

10 2.8±1.3

1.8±1 N

D

1.4±0.7 N

D

6.2±2.1 13.4±4.6

17.4±6 N

D

ND

1.3±0.6

CO

D3, m

g/L

NA

26±15.3

17.5±3.7 11±8.5

10.3±10.5 8.5±7

29.5±2.5 59.5±12.4

63.8±15.8 9.8±6.2

6.5±3 20.3±14.9

Am

mo

nia, m

g/L-N

N

A

0.2±0.2 0.2±0.1

0.1±0.1 0.1±0

0.1±0 0.1±0

0.1±0.1 0.1±0

0.1±0.1 0.1±0

0.1±0 N

itrate

, mg

/L-N

10 4.13±1.08

5.03±0.31 0.19±0.15

ND

N

D

ND

N

D

ND

0.05±0.04

ND

N

D

Nitrite

, mg

/L-N

1 0.37±0.19

0.43±0.13 N

D

ND

N

D

ND

N

D

ND

N

D

ND

N

D

Ortho

pho

spha

te, m

g/L-

P N

A

0.35±0.3 0.45±0.38

ND

N

D

ND

N

D

ND

N

D

0.17±0.08 0.53±0.41

0.36±0.29

Ha

rdne

ss, mg

/L-Ca

CO

3 N

A

225±17.3 220±8.2

270±8.2 352.5±15

367.5±37.7 230±18.3

202.5±15 200±29.4

257.5±9.6 367.5±42.7

355±37

Arse

nic, m

g/L

0.01 0.005±0.003

ND

N

D

ND

N

D

0.004±0.002 0.003±0.001

0.005±0.003 0.004±0.002

0.006±0.002 0.006±0.003

Co

pp

er, m

g/L

1.0 0.026±0.022

0.01±0.005 0.004±0.002

0.005±0.002 0.007±0.002

ND

N

D

0.012±0.02 0.008±0.003

0.016±0.003 0.053±0.072

Chro

mium

, mg

/L 0.05

ND

N

D

ND

N

D

ND

N

D

ND

N

D

ND

0.002±0.002

ND

Sele

nium, m

g/L

0.05 N

D

0.004±0.002 0.004±0.002

ND

N

D

ND

N

D

ND

N

D

ND

0.004±0.003

Zinc, m

g/L

5.0 0.06±0.02

0.08±0.02 0.01±0.01

ND

0.01±0

ND

N

D

0.03±0.04 0.01±0

ND

0.01±0.01

Boro

n, mg

/L 1.0

0.49±0.01 0.47±0

0.5±0.03 0.5±0.08

0.53±0.1 0.43±0.02

0.36±0.04 0.27±0.03

0.52±0.01 0.58±0.06

0.57±0.06 M

ag

nesium

, mg

/L N

A

19.5±0.7 19.7±0.6

20.7±0.6 22.3±0.6

23.7±2.1 19.3±1.2

19.3±1.5 22.3±2.5

21.3±0.6 25.7±1.5

26.3±1.5 C

alc

ium, m

g/L

NA

54.5±6.4

56.3±2.1 77±1.7

106.7±5.8 113.3±5.8

61.3±3.5 48.3±5.1

39.3±6.7 69.3±2.1

116.7±5.8 106.7±5.8

TSS4, m

g/L

10 18±6.1

1.8±1.2 N

D

ND

0.4±0.4

ND

0.4±0.4

0.5±0.4 1.8±1.9

0.5±0.4 0.4±0.4

*Ma

ximum

co

ntam

inatio

n leve

l req

uirem

ents fo

r ab

ove

gro

und no

n-p

ota

ble

uses. 1To

tal o

rga

nic c

arb

on. 2Five

-da

y bio

che

mic

al o

xyge

n de

ma

nd. 3C

hem

ica

l oxyg

en d

em

and

. 4Tota

l suspe

nde

d so

lids. N

A m

ea

ns nota

pp

lica

ble

. Red

fonts ind

ica

te e

xce

ed

anc

e o

f reg

ulato

ry limits. The

numb

er o

f sam

ple

s co

llec

ted

is n=4


APPENDIX 2 - RAINWATER VERSUS LAR WATER QUALITY

The Studio installed rainwater cisterns to capture runoff generated from the roof and parking structure onsite during the winter of 2015/2016. In July 2016, the Studio requested Geosyntec to collect water samples from selected rainwater cisterns across the site to evaluate their water quality. The water quality results for these cisterns are presented in Table 7 with LAR water shown as a comparison.

Rainwater stored in the cisterns was less contaminated than the LAR water. It contained lower levels of dissolved solids (conductivity and hardness), biodegradable organics (BOD5), nutrients (ammonia, nitrite, nitrate, orthophosphate), and metals compared to LAR water. In contrast, zinc concentrations in rainwater were noticeably higher than that collected from the LAR water. Elevated zinc concentrations in harvested rainwater could be associated with the roof materials and the deposition of suspended zinc particulates from vehicles and the environment.

Total suspended solid concentrations were also low. This could be due to the fact that the water had been stored in the cisterns since early 2016. This allowed time for solids and particulates to settle. BOD5 concentrations were below the detection limit of 1 mg/L in harvested rainwater while COD concentrations ranged from 8 to 23 mg/L. High COD suggests that organics present were predominately oxidizable organics.

Indicator bacteria levels in rainwater were also measured. Harvested rainwater contained very low levels of FIB. E. coli counts were below the detection limit of 1 MPN/100mL, which is also below the 2.2 MPN/100 mL criterion specified in the NSF standards specified in the 2016 Guidelines. Low levels of total coliform were found in all tanks except for R4 (the confluence point) where the total coliform count was measured at 538 MPN/100mL.


Table 7 Water Quality Data of Captured Rainwater Stored in Cisterns Onsite and LAR Water

Criteria Rain Cistern Locations LAR Water Quality Parameters

LACDPH 2016

R1 R2 R3 R4 R5 R6 Avg.

TOC, mg/L NA 2.13 3.10 1.30 4.43 1.20 0.88 10.9 BOD5, mg/L 10 ND ND ND 2.43 ND ND 2.8 COD, mg/L NA 10.33 24.50 13.00 22.67 21.50 8.00 26 Ammonia, mg/L-N NA 0.05 ND ND 0.26 ND ND 0.2 Nitrate, mg/L-N 10 0.51 0.95 ND 0.57 0.73 0.61 4.13 Nitrite, mg/L-N 1 ND ND ND ND ND ND 0.37 Orthophosphate, mg/L-P NA 0.19 ND ND 0.21 ND ND 0.35

Hardness, mg/L-CaCO3

NA 48.67 13.50 6.25 9.30 6.35 6.60 225

Arsenic, mg/L 0.01 ND ND ND ND ND ND 0.005 Copper, mg/L 1.0 0.009 0.009 0.006 0.008 0.006 0.007 0.026 Chromium, mg/L 0.05 ND ND ND 0.002 ND ND ND Selenium, mg/L 0.05 ND ND ND ND ND 0.006 ND Zinc, mg/L 5.0 0.150 0.195 0.235 0.242 0.230 0.265 0.060 Boron, mg/L 1.0 0.051 0.017 0.008 0.012 0.013 0.012 0.49 TSS4, mg/L 10 2.37 ND ND 2.37 0.68 1.03 18.4

Turbidity, NTU NA 0.67 -- -- 0.37 -- 0.56 Conductivity, µs/cm 900 22.17 -- -- 29.80 -- 32.75 1061 Fecal Coliform, MPN/100 mL NA ND -- -- ND -- -- 14.6*

Total Coliform, MPN/100 mL 2.2 1.26 3.58 4.12 537.5 2.79 2.00 251.4*

Enterococcus, MPN/100 mL NA 1.26 ND ND ND ND 9.64 19.2*

E. Coli, MPN/100 mL 2.2 ND ND ND ND ND ND -- Note: *Geomean values, n = 2 samples.


APPENDIX 3 - MATERIALS AND METHODOLOGY

LAR Water This pilot study used water extracted from the LAR at the location shown in Figure 1. Approximately 8,000 gallons of water from the LAR was extracted and delivered weekly to the site via a water truck (Figure 13a). The water extraction processes involved placing a floatable pump directly on top of the river bank where water was shallower to prevent the pump from getting washed off (Figure 13b).

Extracted water was stored in two 5,000-gallon storage tanks installed in series on site as an influent water supply for the wetland systems. Screening was provided to prevent large solids, as well as snails, from entering the storage tanks

and eventually into the treatment systems (Figure 14a). The 5,000-gallon tank used to store LAR water prior to distribution to the wetland systems is referred to as the “influent tank” in this report. Water from the influent tank was pumped to an elevated 50-gallon intermediate tank for gravity flow distribution (Figure 14b).

Pilot Wetland Systems Three pilot wetland systems were deployed (Figure 15). Each wetland system consisted of nine wetland cells linked together in series. Each cell was a 7.8 ft L x 3.8 ft W x 3.0 ft D fiberglass tank that had holes pre-set at 8 inches and 4 inches from the top of the edge of the tank on the influent and effluent

Figure 13 a) Water truck; b) floatable pump

Figure 14 a) Influentstorage 1 at the lower level and fabric filter installation prior to refilling the storage tanks; b) influent storage 2 and the intermediate tank


sides, respectively. The elevation difference between these two holes created a fixed hydraulic head of 4 inches across the length of each wetland cell. Individual tanks were connected using one-inch clear flexible tubing. Influent flowed into standing pipes and was subsequently distributed over the width of the wetland via a horizontal perforated pipe that was fixed at the bottom of each wetland cell. Effluent was collected from another perforated pipe located about 2.5 inches below the soil surface on center at the other end of each wetland cell. Such an arrangement allowed for a horizontal upward flow regime within the wetland cells as well as enhanced aeration between wetland cells.

The first eight cells of the three wetland systems were made of three different materials: 1) 3/8 gravel (gravel wetland, A); 2) coconut coir dust mixed with coconut coir pieces (coconut wetland, B); and 3) expanded clay pellets (clay wetland, C). The ninth cell in the gravel (A9) and the clay (C9) wetland systems consisted of coarse sand; while the ninth wetland cell in the coconut wetland (B9) contained coconut coir dust. The site layout of these three wetland systems is presented in Figure 15.

Figure 15 The pilot wetland site plan

To promote the use of native vegetation, six native Southern California wetland plant species were selected and planted in each wetland cell. These plant species were Schoenoplectus californicus (a.k.a. Scirpus californicus), Schoenoplectus americanus (a.k.a. Scirpus americanus), Juncus xiphoides, Bidens laevis, Pluchea purpurascens (PP), and Minulus guttatus (MG). The plants were arranged to enhance aesthetics of the

Sampling Locations

Effluent TankInfluent Tank

A1A2A3A4A5A6A7A8A9

B1B2B3B4B5B6B7B8B9

C1C2C3C4C5C6C7C8C9 Cin

INT

LAR

EFT

ee ee ee ee ee ee ee ee eenn nn nn nn nn nn nn nn nn




wetlands by planting the larger species in the middle and the dwarf species along the edge. The layout of the plants is presented in Figure16.

Figure 16 The layout of the wetland plants in each wetland cell.

Flow Rate Control and Recording

Three McMillan S-Series Model S-111Microturbine Flo-Meters were installed at the influent of cells 1 of each system to measure and record flow rates during the study period. These flow meters were rated to measure low flow rates in a range of between 0.013 and 10 liters per minute (lpm) with an accuracy of ± 1.0% (McMillan, 2016). Each flow meter was paired with a Cole-Parmer multi-turn needle tip valve to allow for precise flow control. Flow rates were also measured manually on a weekly basis for comparison. Figure 17 shows the location of the valve and the flow meter installed in the three system.

Figure 17 A flow control and recording setup installed at the influent of the clay pellet wetland, C.


Water Quality Sampling and Analysis

Grab samples were collected between May and August, 2016 for laboratory analysis and onsite measurements. Grab samples to be sent to a certified laboratory for analysis were preserved in coolers (<4˚C). Water quality parameters analyzed in the laboratory were FIB (total coliform, fecal coliform, Escherichia coli, enterococci), organics (five-day biochemical oxygen demand (BOD), total organic carbon (TOC), chemical oxygen demand (COD), nutrients (orthophosphate, ammonia, nitrite, and nitrate), heavy metals that are known to be commonly found

in the LAR (chromium, arsenic, selenium, copper, and zinc), total suspended solids, boron, and hardness. FIB analyses were conducted twice weekly, and the remaining water quality parameters were analyzed weekly.

Turbidity (La Motte 2020we, Chestertown, MD), temperature, oxidation-reduction potential (ORP), conductivity, total dissolved solids, pH (YSI ProDSS, YSI, Yellow Springs, OH), and chlorophyll (YSI 650MDS, YSI, Yellow Springs, OH) were measured in the field twice weekly. The methods used for the onsite measurements are presented in Appendix 2.

In addition to routine sampling, a suite of one-time special sampling was conducted after the outbreak of iron bacteria overgrowth was observed in the first three cells of the clay pellet wetland systems (C1-3). The water quality parameter suite tested was total iron, ferric ion, ferrous ion, sulfate, and manganese.

Hydraulic Retention Time and Tracer Tests

The theoretical hydraulic retention time (tHRT) of each cell was calculated based on the effective porosity (ε) of the media. Both clay pellets and coconut coir are porous materials. In the calculation, it was assumed that fine pores in individual media did not contribute to water flow within individual wetland cell. Presoaked clay pellets and coconut coir was used. The measured effective porosities of gravel, coconut coir, and clay

Figure 18 An effluent sampling port located at the end of each wetland cell


pellets were 34%, 36%, and 41%, respectively. The porosity data were used to calculate the operational flow rate to yield a tHRT of one day per cell using the relationship presented in Equation 1.

Equation 1 Operational flow rate

𝑄 =𝜀𝑉

𝑡𝐻𝑅𝑇

Where Q = operational flow rate ε = the effective porosity V = total volume (media + void spaces) tHRT = theoretical hydraulic retention time

The mean hydraulic retention time in these three systems was measured by performing rhodamine WT dye (RWT) tracer tests. RWT was selected for its ease of use, relatively low cost, low adsorptive tendency in siliceous materials, strong fluorescence, high diffusivity, chemical stability, and benign character in aquatic environment (Kadlec, R.H. & Wallace, S.D., 2009). In-situ RWT concentration detection and recording were achieved using three YSI 6130 RWT sensors that were attached to three YSI 6820 sondes for data collection purposes. These sensors were calibrated by the vendor according to the procedures specified by the manufacturer.

Prior to the tracer tests, the RWT background concentrations were measured at Cells 1, 4, and 9 on a 5-minute interval for 24 hours. Additionally, RWT sorption potential for coconut coir and clay pellet media was evaluated by mixing the media in containers filled with a known RWT concentration. The RWT concentrations in each container were measured after 24 hours to determine the extent of RWT sorption. Such information was used to adjust the quantity of dye added to the cells to yield the desirable peak RWT concentration. It was determined that the volume of the dye volume required were 1 mL, 4mL, and 2mL of 2.5% RWT for the gravel, coconut coir, and clay pellet cells, respectively.

The RWT concentration change was measured and recorded at end of the cell outlet. The sensors remained in the cell outlet until the most of the


tracer tail was captured. The data collected from the tracer tests were used to determine the average cell hydraulic retention time using Equation 2 below.

Equation 2 Mean hydraulic retention time of tracer in the wetland, t’, mins

𝑡 =∫ 𝐶𝑡 𝑑𝑡

∫ 𝐶 𝑑𝑡

Where t’ = mean hydraulic retention time of tracer in the wetland, min C = concentration exiting the wetland at time t, µg/L t = time since addition of tracer pulse to influent port, min

The exit concentration and the time were normalized using Equations 3-5.

Equation 3 Normalized time

𝜃 =𝑡𝑡′

Where θ = normalized time

Equation 4 Total mass concentration of mass recovered

𝐶 = 𝐶𝑑(𝜃) = ∫ 𝐶 𝑑𝑡

𝑡′Where CN = total mass concentration of tracer recovered, µg/L

Equation 5 Normalized concentration

𝐸(𝜃) = 𝐶𝐶

Where E (θ) = normalized concentration

Capital and O&M Evaluation

Capital and operation and maintenance (O&M) costs are an important decision factor for technology selection. A common operational challenge for HSSF wetland systems is clogging from biofouling or solids accumulation. Improperly designed pretreatment processes often exacerbate clogging extent and frequency. Remedy for HSSF wetlands


that are clogged with solids are either removing accumulated solids or replacing the bed. If such maintenance activities are performed frequently, it will add significant costs to the overall operations. The normal O&M costs and incidental repair costs are expected to differ for these three HSSF wetlands. Accordingly, an evaluation of the capital and O&M costs was conducted based on the experience and lessons learned from operating these wetland systems.

Rainwater Cisterns

Metabolic Studio installed rainwater cisterns across the property site that captured and stored roof runoff for irrigation water use during dry weather seasons. A total of 60,000 gallons were collected from four roof structures during the previous rainy season. To characterize the water quality of the stored rainwater, water samples were collected from six locations to evaluate bacteria, organics, nutrients, and metals. Water quality parameters tested in the laboratory were identical to those routinely tested parameters for the pilot wetland study.

In order to distribute the LA River water captured by Bending the River Back Into the City, it must first be treated to meet state and local water-quality requirements. As sophisticated natural water treatment systems, wetlands are capable of removing many contaminants, including metals, nutrients, and bacteria. Three modular subsurface-flow wetland systems were constructed on the Studio's Undevelopment 1 site on the banks of the LA River. Each contains different soil media — gravel, coconut coir, clay pallets. These modular pilot wetlands were planted with locally sourced native California wetland plant species. This pilot wetland report evaluates the treatment performance of these wetland systems to determine which type of soil media, the required residence time, and what operating conditions make the biggest difference in helping meet the treatment goals of Bending the River Back Into the City. Metabolic Studio's pilot Wetland Study Performance Report confirms that wetlands are a suitable method for treating LA River water.

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Documents

Metabolic Studio Pilot Wetland Study Report…requiring little energy input, and reducing carbon dioxide (a greenhouse gas). The reported treatment performance and benefits above led