P&T RegenOx ORC Adv in Herts UK

Integrated Physical – Chemical – Biological Remedial Strategy for TPH Impacted Groundwater Service Station, Hertfordshire, UK Historical operations at a service station in Hertfordshire resulted in petroleum hydrocarbon contamination in soil and groundwater. The site was demolished and was to become a residential development with underground parking. Shallow soil samples and groundwater monitoring were conducted to determine the extent of total petroleum hydrocarbon (TPH) contamination. Shallow soils impact was associated with a former tank farm and was limited to the northern portion of the site. A TPH concentration of 3,600 milligrams per kilogram (mg/kg) was observed in the vicinity of borehole WS1 (<0.5m bgl). The maximum TPH concentrations observed in groundwater were 53 milligrams per liter (mg/L) and 34 mg/L at locations MW4 and MW1, respectively (Figure 1). Remedial Strategy The remedial objective was to reduce concentrations of TPH and benzene in soil and groundwater to the site specific target level (SSTL) of 10 mg/L. However, due to WS3 WS1 the presence of a chalk formation underlying the site, a significant proportion of the identified contamination WS2 would persist as a result of the dual porosity nature of WS8 the chalk formation. For this reason, the most effective remedial solution was determined to be groundwater WS4 abstraction using a down‐well pump and treat (P&T) WS9 WS5 system, in combination with RegenOx™ augmentation WS7 WS6 to address the sorbed material. A phased remedial WS10 approach optimised treatment whereby the Phase 1 WS12 WS11 P&T removed the bulk of the impact from the fractures. However, post pumping rebound resulted from the hydrocarbons in the formation pore spaces coming into Figure 1. Service Station Site Map solution. RegenOx was used to target the hydrocarbon contamination by chemical oxidation whilst also making it more available for removal during the second phase of the P&T operation. ORC Advanced® was used as a polishing step to aerobically degrade any remaining petroleum hydrocarbon contamination to the SSTL. System Augmentation using RegenOx™ RegenOx™ is a proprietary two‐part chemical oxidation product developed and sold by Regenesis for in situ groundwater treatment. It combines the use of a controlled‐release percarbonate‐based oxygen compound with a proprietary multi‐part catalyst to generate surface‐mediated free‐radical generation and contaminant oxidation (e.g. perhydroxyl radical, hydroxyl radical and superoxide radical), with reactive power comparable to that of Fenton’s reagent but with much easier handling and subsurface delivery / longevity (up to 30 days). This provides an effective contaminant oxidation reaction without violent exothermic reaction, and can therefore be handled using a wide range of standard field equipment (e.g. direct push injection rigs) or applied directly to excavations.

Augmentation of the P&T system using chemical oxidation allowed for enhanced recovery of petroleum hydrocarbons from soil and groundwater. This occurs as a result of the powerful desorption‐surfactant effect of RegenOx (principally the catalyst) that draws the contaminant off the soil surface and into solution. The contaminant then reaches the catalytic surface where localised free‐radical generation occurs, leading to focused contaminant destruction. This restricts the oxidant losses onto tightly bound and Table 1. Subsurface Details heavier soil organics such as humic, roots, and Soil Type Glaciofluvial clays and chalk other natural or immobile fractions. As a result Depth to Groundwater 10m of the above processes, RegenOx‐desorbed Treatment Area 300 m2 contaminant mass and partially oxidised (more soluble) organic species are recovered via Treatment Thickness 3m groundwater abstraction using the existing P&T Table 2. RegenOx Application Details system, whilst further contamination is destroyed in situ by oxidation. Enhanced Application Type Fixed point – through P&T abstraction points biodegradation using ORC Advanced, as a polishing step, was applied following the RegenOx Part A – 16.4 kg/m Application Rate (avg) RegenOx treatment to target residual dissolved RegenOx Part B – 16.4 kg/m phase contamination and reach the SSTL. Table 3. ORC Advanced Application Details RESULTS Application Type Fixed point Initial pumping/free product removal activities Application Rate 9.07 kg/m proved very successful, having achieved a 60% reduction in average total TPH concentration TOTAL REGENOX <£9,000 within the first four months of operation. MATERIAL COST However, upon shutdown of the P&T system, rebound was observed at all locations (MW1 to TOTAL PROJECT COST ~£80,000 MW6) as a result of desorption. The system was then augmented using RegenOx to target the sorbed phase. Shortly following augmentation of the P&T system, an anticipated increase in dissolved phase TPH was observed. Following this increase, the P&T system was switched on and the ‘rebound’ abstracted, thus making the physical removal of the TPH impaction much more effective. The RegenOx applications were repeated approximately 2‐4 times, depending on location, between April 2008 and July 2008. Once the dissolved phase contamination was reduced to a level suitable for aerobic bioremediation, an ORC Advanced injection was completed in all wells to target residual TPH concentrations in groundwater. The combined P&T, RegenOx and ORC Advanced treatment was effective at reducing TPH to below the SSTL of 10 mg/L in all wells. An average 99% reduction in average Total TPH was reported in September and October 2008. No further rebound was observed after this time. In addition, the combined treatment approach reduced the time taken to achieve the remedial targets from an estimated 12 months using P&T alone to 6 months using a combined treatment approach.

Pumping RegenOx ORC Adv Remedial Target CONCLUSIONS As a result of the integration of RegenOx and ORC Advanced with a physical treatment system, petroleum hydrocarbon concentrations were reduced quickly and cost effectively. RegenOx augmentation of the pumping system on site allowed for reduced pumping time and faster decommissioning. It is estimated that the combined treatment approach allowed for the entire treatment time frame to be reduced from 12 months using P&T alone to 6 months with the RegenOx & ORC‐Advanced material costs totaling approximately only 10% of the total project costs. The ORC Advanced application enhanced the biodegradation of the residual contamination and effectively reduced TPH concentrations to the target goal. An average 99% contaminant reduction was reported across the treatment area and concentrations of TPH were reduced to below the SSTL of 10 mg/L in all wells of concern. Successful regulatory sign off was achieved due to the overall reduction in TPH concentrations. WD Environmental Land Clean Ltd Regenesis Ltd Simon Ware Mark Swanston Gareth Leonard +44 (0) 1442 825570 +44 (0) 1730 23478 +44 (0) 1833 630411 sware@wdenvironmental.com mark.swanston@landclean.net gleonard@regenesis.com www.wdenvironmental.com www.landclean.net www.regenesis.com

P&T RegenOx ORC Adv in Herts UK

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