Laboratory studies have been conducted at the Civil & Environmental Engineering Laboratories at the University of Connecticut (UCONN) to assess the SedFirst technology. The studies have evaluated the SedFirst treatment impact on sand cohesion, PAC and GAC placement in a sand cap application, sediment resuspension mitigation, Organoclay-sand cap erosion resistance enhancement and mudflat soft sediment shear stress resistance enhancement.
PAC/Sand Placement Study
A study to evaluate the effect of the SedFirst treatment on enhancing PAC placement in a sand cap application has been conducted. The comprehensive testing evaluated four different PAC materials, including lignite coal PAC, bituminous PAC, and coal/wood-based PAC. Sand from a sand quarry in New Jersey was used in the study. Water turbidity was measured after placing mixes of sand and PAC in a water column in glass cylinders. SedFirst-treated and untreated mixes were evaluated.
The results indicate that 0.5% SedFirst (SED-3) performed well at reducing turbidity for placement of bituminous coal-based PAC (NTUs < 10 at 5% and 10% PAC dosages) and blends of coal/wood-based PAC (NTUs < 10 at 5% PAC dosage). The reductions in turbidity were > 99% when compared to the control tests (untreated sand/PAC mixes). The treatment resulted in a homogeneous Sand/PAC mixture (no stratification).
The results also indicate that 0.75% SedFirst (SF-2) performed well on PAC composed of lignite coal-based PAC carbon (NTUs < 10 at 5% PAC dosage). The reductions in turbidity were > 94% when compared to the control tests (untreated sand/PAC mixes). The treatment resulted in a homogeneous Sand/PAC mixture (no stratification).
The study also evaluated the effect of moisture content in the sand from 10 to 30% and determined this as an appropriate range to achieve the desired turbidity reduction of sand/PAC mixes treated with SedFirst.
Sand Cohesion Study
This study was conducted to assess the cohesion-enhancing properties of the SedFirst treatment by measuring direct shear strength (ASTM D3080) and Unconfined Compressive Strength (UCS) of treated sand and soil. The SedFirst treatment increased significantly (greater than 10-fold) the cohesion and compressive strength of cured sand samples up to a dosage of 10 g/kg (1%). Enhanced cohesion generated by the SedFirst treatment is dependent on water saturation, curing time and temperature, among other parameters.
Organoclay/Sand Placement Study
This laboratory study evaluated the shear stress resistance of saturated sand/Organoclay mixes in order to assess the potential erosion resistance of such mixes in field applications. Sand and Granular Organoclay (2 & 4% by weight) were mixed with .5 and 1% SedFirst and saturated with water. The samples were sheared as mixed with no heating or curing. The results indicate that the SedFirst (SF-6) treatment can significantly enhance the cohesion of Organoclay-amended sand. The treatment provided the highest cohesion values (1.60 at 0.5% dosage and 2.55 at 1% dosage) for the 2% Organoclay-amended saturated sand.
Silty Clay 1.89 psi
Silty or Clayey Fine Sands 1.02 psi
Silty Sand 3.19 psi
Control, Sand Only — Cohesionless
Mudflat Soft Sediment Stabilization Study
This study was conducted to assess the direct shear impact and turbidity reduction of two SedFirst treatments (SED1 and SED3) on mudflat material from Good Luck Point Bay in Bayville NJ. This treatment approach may reduce significantly the amount of material NJDOT would need to dredge to maintain navigation channels, and would minimize the environmental impact of dredging applications.
The results of the treated saturated soft sediment experiments indicate that shear stress increases with increasing PPB concentration (SED1 and SED3). Concentrations as low as 0.5% by weight result in measurable shear stress for both PPB treatments indicating that treatment of mudflat soft sediment with either PPB formulation would likely result in reduced erosion.
GAC/Sand Placement Study
This preliminary laboratory study evaluated the impact of the SedFirst treatment on the turbidity of sand/GAC mixes when placed through a water column. The results indicate that the treatment can mitigate the gravity segregation of GAC and sand during placement and minimize the dispersion of GAC and fine sand/silt in the water column. The treatment resulted in a homogeneous Sand/PAC mixture (no stratification).
Picture 1: Control vs Sand, 5% GAC, 1% SED-1
Picture 2: Close up of control vs SED-1 Treated. Note uniform GAC distribution
Aquatic Toxicity Testing
Aquatic toxicity testing was conducted at a certified laboratory, New England Bioassay (NEB), in Manchester, CT, to asshess toxicity of a PPB amendment (SandFirst SED-1). The procedures followed the protocols described by the United States Environmental Protection Agency (USEPA) in "Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms" (EPA-821-R-02-012). Duration of the tests was 48 hours for the C.dubia and 96 hours for the fathead minnow, mysid shrimp and Menidia. Each test consisted of three control replicates (which did not contain sand, to verify organism health without the interference of sand) and five replicates containing sand and overlying water, each with 10 organisms per replicate. Laboratory water used for the freshwater species (C.dubia and P.promelas) was moderately-hard reconstituted freshwater. Laboratory water used for the saltwater species (Mbahia and Mberyllina) was 25 ppt artificial saltwater. For the C.dubia, 100 ml beakers were used with 20 ml of sand covering the bottom of the beaker. For the fathead minnow, mysid shrimp and Menidia, 1-liter beakers were used with 200 ml of sand covering the bottom of each beaker. Two tests were run for each species, one with untreated sand, and one with sand treated with l0 g/kg (1%) of SED1. The results of the testing indicate that the SED-1 treatment passed the aquatic acute toxicity tests (> 90% survival of the various organisms ). thus, no negative impact is expected from the use of the SandFirst and SedFirst products in-situ.