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Smith D.P.,Applied Environmental Technology Tampa Inc.
Water Science and Technology | Year: 2012

A passive biofiltration process has been developed to enhance nitrogen removal from onsite sanitation water. The system employs an initial unsaturated vertical flow biofilter with expanded clay media (nitrification), followed in series by a horizontal saturated biofilter for denitrification containing elemental sulfur media as electron donor. A small-scale prototype was operated continuously over eight months on primary wastewater effluent with total nitrogen (TN) of 72.2 mg/L. The average hydraulic loading to the unsaturated biofilter surface was 11.9 cm/day, applied at a 30 min dosing cycle. Average effluent TN was 2.6 mg/L and average TN reduction efficiency was 96.2%. Effluent nitrogen was 1.7 mg/L as organic N, 0.93 mg/L as ammonium (NH 4-N), and 0.03 as oxidized (NO 3 +NO 2) N. There was no surface clogging of unsaturated media, nitrate breakthrough, or replenishment of sulfur media over eight months. Visual and microscopic examinations revealed substantially open pores with limited material accumulation on the upper surface of the unsaturated media. Material accumulation was observed at the inlet zone of the denitrification biofilter, and sulfur media exhibited surface cavities consistent with oxidative dissolution. Two-stage biofiltration is a simple and resilient system for achieving high nitrogen reductions in onsite wastewater.

Smith D.P.,Applied Environmental Technology Tampa Inc.
World Environmental and Water Resources Congress 2012: Crossing Boundaries, Proceedings of the 2012 Congress | Year: 2012

Biofiltration shows promise as an appropriate technology to increase nitrogen removal in onsite wastewater treatment systems. This presentation will summarize ongoing studies of passive, two-stage biofiltration systems for onsite nitrogen removal that have been funded by the Florida Department of Health. Passive systems utilize a single pump, no aerators, and reactive media for denitrification. Biofilter media include expanded clay, natural zeolite, silica sand, elemental sulfur, lignocellulosics, limestone and oyster shell. Over twenty biofilters have been operated in upflow, downflow, horizontal flow, and in saturated and unsaturated configurations, all fed by primary effluent. Total nitrogen reductions of 95% have been achieved. Oxygen transfer analysis suggests that the unsaturated biofilter designs provide high oxygen ingress rates that support efficient nitrification. Simulation modeling shows high denitrification rates at the entrance region of sulfur biofilters and agrees qualitatively with field observations. The goal of the pilot study and process modeling is to produce functional designs for nitrogen reducing systems at single family residence and larger scale. © ASCE 2012.

Smith D.P.,Applied Environmental Technology Tampa Inc.
Journal of Environmental Engineering (United States) | Year: 2015

The plenum-aerated biofilter (PA biofilter) is an unsaturated, single pass vertical flow biofilter with horizontal air plena within the media to enhance passive aeration. Plena enlarge the surface area of the air/media interface, increase oxygen ingress, and permit a reduction in the footprint of ammonium oxidizing biofilters. An experimental PA biofilter was operated on household wastewater pretreated in a primary settling tank. The prototype was a 7.3 cm (3 in.) inner diameter circular column, containing 61 cm (24 in.) of granular clinoptilolite media. Three 5.1 cm (2 in.) aeration plena were placed at successive 7.6 cm (3 in.) media thicknesses below the upper filter surface. The biofilter was operated for 28 weeks at hydraulic loading of 69.8∈∈cm/day (17∈∈gal./ft2-day) and a 60-min dosing cycle. Performance was characterized by monitoring from days 180 to 196. Influent NH4+-N was reduced by 99% (mean 51.6∈∈mg/L to 0.61∈∈mg/L, n=3), with substantial conversion to NO3 - N (mean 38.4∈∈mg/L, n=3). Solute profiling showed ammonia reduction was substantially complete after passage through 45 cm (18 in.) of porous media and nitrite accumulated between 15 and 30 cm (5.9 and 11.8 in.). This short-term study suggests that the PA biofilter can provide a compact and passive ammonium oxidation system that is suitable for on-site wastewater treatment. Further studies are needed to verify that effective nitrogen transformations can be sustained over longer periods of operation. © 2015 American Society of Civil Engineers.

Smith D.P.,Applied Environmental Technology Tampa Inc.
Journal of Environmental Engineering | Year: 2010

A methodology was developed to monitor and evaluate the removal of solids and associated constituents by a nutrient separating baffle box (NSBB) storm-water treatment device treating runoff from a 4.3 ha (10.6 acre) residential watershed discharging into the Indian River Lagoon, Florida. The NSBB was monitored over a 359-day time period using autosamplers to quantify water column removal during runoff events, and by quantifying and analyzing solids that accumulated within the NSBB. Flow composited influent and effluent samples were collected to represent water column performance. Event mean concentration (EMC) reduction was moderate (mean: 17%) and variable (range: -39 to 68%) for suspended solids, and negative for nitrogen, phosphorus, fecal coliforms chromium, and copper. The mass of solids that accumulated in bottom chambers and in a strainer screen was quantified and analyzed for nitrogen, phosphorus, heavy metals, and polycyclic aromatic hydrocarbons. A quantitative evaluative framework was devised to estimate the total pollutant mass removal by NSBB, which consisted of the summation of the separately calculated mass removals for water column, bottom chamber material, and strainer screen material. The water column accounted for only 4% of total solids that accumulated in the NSBB, which was equally divided between bottom chamber and strainer screen. Removal of nitrogen, phosphorus, and metals could be accounted for only by considering mass accumulations. Results suggest that overall assessment of pollutant removal by NSBB must be cognizant of the materials not captured by typical autosamplers: larger size sediment particles, large floating and suspended matter, and the pollutants associated with these materials. Using water column EMCs as the sole measure of performance significantly underestimated loading reduction of storm-water constituents by the NSBB. The monitoring and evaluative methodology applied to the NSBB may be applicable to load reduction evaluations for other storm-water treatment devices with a similar function. © 2010 ASCE.

Smith D.P.,Applied Environmental Technology Tampa Inc. | Smith N.T.,University of Maryland University College
Bioresource Technology | Year: 2015

An anaerobic-ion exchange (AN-IX) process was developed for point-of-origin recovery of nitrogen from household wastewater. The process features upflow solids-blanket anaerobic treatment (ammonification) followed by ammonium ion exchange onto natural zeolite. The AN-IX system is configured as a series of linked upflow chambers that operate passively without energy input, and is amenable to intermittent and seasonal operation. A 57L prototype was operated for over 1.8years treating actual wastewater under field conditions. Total nitrogen removal exceeded 96% through the first 160days of operation and effluent ammonium nitrogen remained below detection for 300days. Ion exchange chambers exhibited sequential NH4+-N breakthrough over extended operation and complete media exhaustion was approached at Day 355. The ammonium capacity of zeolite was estimated as 13.5mg NH4+-N per gram dry weight. AN-IX is a resilient and cost effective process for local-scale nitrogen recovery and reuse, suitable for small scale and larger systems. © 2015 Elsevier Ltd.

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