1. Urban Bioswale Efficacy Monitoring
2. Integrated Vegetated Agricultural Drainage Ditch Efficacy Monitoring
Urban Bioswale Efficacy
During the 18.5 h of the storm, 1.52" of rain was recorded by the rain gauge, and this resulted in 50,490 gallons of water flowing from the parking lots into the bioswale. Of this total volume, 5,248 gallons were recorded by the outlet flow meter, resulting in a total infiltration of 90% of the stormwater that flowed into the bioswale. The bioswale reduced all of the chemicals monitored. Total suspended solids were reduced 72% (Table 1). Concentrations of PAHs were very low when they were detected, but all concentrations of PAHs were reduced by 100%. All metals were reduced in the outlet samples. Zinc and copper were reduced by 97% and 92%, respectively (Table 1). A number of pyrethroid pesticides were detected in the inlet samples and all of these were reduced in the outlet samples. Total pyrethroid concentrations were reduced 99%. Toxic concentrations of the pyrethroids bifenthrin, cypermethrin, lambda-cyhalothrin, and permethrin were detected in the inlet samples, and were reduced to concentrations below median lethal concentrations (LC50s) for H. azteca in the outlet samples (Table 1). For example, bifenthrin was detected at a toxic concentration in the inlet sample and was reduced by 93% in the outlet sample.
Treatment of the phenylpyrazole pesticide fipronil was inconsistent. The parent compound of fipronil was detected in the inlet sample and was reduced by 100% in the outlet sample. The fipronil degradates, fipronil desulfinyl and fipronil sulfone were detected in the inlet sample. The desulfinyl degradate was reduced 100% in the outlet sample, but the sulfone degradate increased by 45%. Possible reasons for the variable treatment of fipronil include its moderate solubility. The neonicotinoid pesticide imidacloprid was not detected in the inlet sample.
Toxicity of the stormwater varied by species tested. None of the inlet samples were toxic to daphnids (Table 1). All inlet samples were toxic to H. azteca and toxicity was reduced by the bioswale. Amphipod survival was 66% in the inlet sample, and improved to 98% in the outlet. Toxicity to C. dilutus survival was observed in inlet and outlet samples. Significant reductions in C. dilutus weight were observed in the inlet sample, and growth significantly improved by 49% in the outlet sample (Table 1).
Integrated Agricultural Vegetated Drainage Ditch Efficacy
Efficacy of the integrated vegetated ditch system to treat chlorpyrifos varied depending on the flow rate, but TSS and chlorpyrifos in spiked irrigation water were significantly reduced at both flow rates. The average TSS reduction in the three trials conducted at 3.2 L/s and 6.3 L/s was 79.7% and 82.3%, respectively. Chlorpyrifos was reduced from about 750 ng/L to less than detection (<50 ng/L) in two of the low flow-rate trials, and to an estimated concentration of 78 ng/L in the third trial (below reporting limit). Chlorpyrifos was reduced from an average of 707 ng/L to less than 100 ng/L in all three trials at the higher flow rate. When combined with infiltration, average load reductions were 98% and 94% for the low and high flow rates, respectively (Table 2).
Complete mortality to C. dubia was observed in all inlet samples (pre-treatment). Two of the 3.2 L/s outlet samples and one of the 6.3 L/s outlet samples were not toxic (Table 2), corresponding to the outlet samples with the three lowest chlorpyrifos concentrations.
Figure 1: Image of a parking lot bioswale. Inlet (untreated) stormwater samples were collected from several of the curb openings to the bioswale. Outlet (treated) stormwater samples were collected from a drainage pipe located inside an overflow grate located at the top of the image (not shown). Please click here to view a larger version of this figure.
Figure 2: Schematic diagram of integrated vegetated ditch system (152 m length, not to scale). Entire ditch was vegetated with red fescue grass. Compost and GAC installations were placed as shown. Please click here to view a larger version of this figure.
Toxicity | Units | Inlet | Outlet |
H. azteca | % Survival | 66 | 98 |
C. dubia | % Survival | 100 | 100 |
C. dilutus | % Survival | 81 | 71 |
Dry Wt. (mg) | 0.39 | 0.77 | |
Quimica | |||
TSS | mg/L | 136 | 38 |
Bifenthrin | ng/L | 5.6 | 0.4 |
Cyfluthrin | ng/L | 1.2 | ND |
Cypermethrin | ng/L | 3.1 | ND |
(Es)Fenvalerate | ng/L | 0.7 | ND |
Fenpropathrin | ng/L | 3.6 | ND |
L-Cyhalothrin | ng/L | 1.3 | ND |
Permethrin | ng/L | 15 | ND |
Fipronil | ng/L | 0.8 | ND |
Fipronil Desulfinyl | ng/L | 0.6 | ND |
Fipronil Sulfide | ng/L | ND | ND |
Fipronil Sulfone | ng/L | 0.6 | 1.1 |
Imidacloprid | ng/L | ND | ND |
Cadmium | µg/L | 0.52 | 0.07 |
Copper | µg/L | 78 | 5.9 |
Lead | µg/L | 11 | 1 |
Nickel | µg/L | 32 | 2.8 |
Zinc | µg/L | 590 | 15 |
Total PAHs | µg/L | 0.47 | ND |
Table 1: Toxicity and chemistry of bioswale inlet and outlet monitored during one storm. TSS = total suspended solids; ND = not detected.
3.2 Liters/second | 6.3 Liters/second | |||||
1 | 2 | 3 | 1 | 2 | 3 | |
Chlorpyrifos (ng/L) | ||||||
Inlet | 638 | 738 | 879 | 282 | 973 | 966 |
Outlet | ND | ND | 78 | 52 | 82 | 58 |
Percent Change | -100 | -100 | -91 | -82 | -92 | -94 |
TSS (mg/L) | ||||||
Inlet | 422 | 588 | 448 | 238 | 218 | 258 |
Outlet | 46 | 66 | 176 | 40 | 52 | 31 |
Percent Change | -89 | -89 | -61 | -83 | -76 | -88 |
Toxicity (% Survival) | ||||||
Inlet | 0 | 0 | 0 | 0 | 0 | 0 |
Outlet | 96* | 100* | 0 | 100* | 0 | 4 |
Control | 96 | 100 | 100 | 96 | 100 | 100 |
Avg. Chlorpyrifos Reduction | 97% | 89% | ||||
Avg. Runoff Infiltration | 52% | 43% | ||||
Avg. Chlorpyrifos Load Reduction | 98% | 94% |
Table 2: Chlorpyrifos concentrations, total suspended solids concentrations, and percent survival in composite samples from replicate trials evaluating the effectiveness of the integrated ditch treatments at two flow rates (3.2 L/s and 6.3 L/s). Asterisk indicates significant reduction in toxicity.
HOBO tipping-bucket digital logger rain gauge | Onset Computer Co., Bourne MA, USA) | Onset RG3 | Rain gauge |
Mechanical geared pulse flow meter | Seametrics Inc., Kent WA | Seametrics MJ-R | Flow meter for measuring bioswale outlet flow |
Filtrexx SafteySoxx | Filtrexx Co. – info@filtrexx.com | SafetySoxx | perforated synthetic cloth for granulated activated carbon and compost |
Granulated activated carbon | Evoqua – Siemens Corp., Oakland CA | AC380 | GAC for agriculture irrigation water treatment |
Digital flow meters | Seametrics Inc. Kent WA | Ag2000; WMP101 | Flow meters for agriculture irrigation treatment system monitoring |
Data Loggers | Campbell Scientific Inc., Logan, UT | CR1000 | Data loggers for recording flow data |
Peristaltic pumps for composite sampling | Omega Engineering Inc. Stamford CT | Omegaflex FPU-122-12VDC | Pumps for composite sampling |
Urban stormwater and agriculture irrigation runoff contain a complex mixture of contaminants that are often toxic to adjacent receiving waters. Runoff may be treated with simple systems designed to promote sorption of contaminants to vegetation and soils and promote infiltration. Two example systems are described: a bioswale treatment system for urban stormwater treatment, and a vegetated drainage ditch for treating agriculture irrigation runoff. Both have similar attributes that reduce contaminant loading in runoff: vegetation that results in sorption of the contaminants to the soil and plant surfaces, and water infiltration. These systems may also include the integration of granulated activated carbon as a polishing step to remove residual contaminants. Implementation of these systems in agriculture and urban watersheds requires system monitoring to verify treatment efficacy. This includes chemical monitoring for specific contaminants responsible for toxicity. The current paper emphasizes monitoring of current use pesticides since these are responsible for surface water toxicity to aquatic invertebrates.
Urban stormwater and agriculture irrigation runoff contain a complex mixture of contaminants that are often toxic to adjacent receiving waters. Runoff may be treated with simple systems designed to promote sorption of contaminants to vegetation and soils and promote infiltration. Two example systems are described: a bioswale treatment system for urban stormwater treatment, and a vegetated drainage ditch for treating agriculture irrigation runoff. Both have similar attributes that reduce contaminant loading in runoff: vegetation that results in sorption of the contaminants to the soil and plant surfaces, and water infiltration. These systems may also include the integration of granulated activated carbon as a polishing step to remove residual contaminants. Implementation of these systems in agriculture and urban watersheds requires system monitoring to verify treatment efficacy. This includes chemical monitoring for specific contaminants responsible for toxicity. The current paper emphasizes monitoring of current use pesticides since these are responsible for surface water toxicity to aquatic invertebrates.
Urban stormwater and agriculture irrigation runoff contain a complex mixture of contaminants that are often toxic to adjacent receiving waters. Runoff may be treated with simple systems designed to promote sorption of contaminants to vegetation and soils and promote infiltration. Two example systems are described: a bioswale treatment system for urban stormwater treatment, and a vegetated drainage ditch for treating agriculture irrigation runoff. Both have similar attributes that reduce contaminant loading in runoff: vegetation that results in sorption of the contaminants to the soil and plant surfaces, and water infiltration. These systems may also include the integration of granulated activated carbon as a polishing step to remove residual contaminants. Implementation of these systems in agriculture and urban watersheds requires system monitoring to verify treatment efficacy. This includes chemical monitoring for specific contaminants responsible for toxicity. The current paper emphasizes monitoring of current use pesticides since these are responsible for surface water toxicity to aquatic invertebrates.