Naturally Wallace Consulting LLC

Raleigh, NC, United States

Naturally Wallace Consulting LLC

Raleigh, NC, United States

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Nivala J.,University of Aarhus | Nivala J.,Helmholtz Center for Environmental Research | Knowles P.,Natural Systems Utilities LLC | Knowles P.,Aston University | And 4 more authors.
Water Research | Year: 2012

This paper reviews the state of the art in measuring, modeling, and managing clogging in subsurface-flow treatment wetlands. Methods for measuring in situ hydraulic conductivity in treatment wetlands are now available, which provide valuable insight into assessing and evaluating the extent of clogging. These results, paired with the information from more traditional approaches (e.g., tracer testing and composition of the clog matter) are being incorporated into the latest treatment wetland models. Recent finite element analysis models can now simulate clogging development in subsurface-flow treatment wetlands with reasonable accuracy. Various management strategies have been developed to extend the life of clogged treatment wetlands, including gravel excavation and/or washing, chemical treatment, and application of earthworms. These strategies are compared and available cost information is reported. © 2012 Elsevier Ltd.


Murphy C.,ARM Ltd | Rajabzadeh A.R.,McMaster University | Weber K.P.,Royal Military College of Canada | Nivala J.,Helmholtz Center for Environmental Research | And 2 more authors.
Bioresource Technology | Year: 2016

In aerated treatment wetlands, oxygen availability is not a limiting factor in sustaining a high level of nitrification in wastewater treatment. In the case of an air blower failure, nitrification would cease, potentially causing adverse effects to the nitrifying bacteria. A field trial was completed investigating nitrification loss when aeration is switched off, and the system recovery rate after the aeration is switched back on. Loss of dissolved oxygen was observed to be more rapid than loss of nitrification. Nitrate was observed in the effluent long after the aeration was switched off (48 h+). A complementary modeling study predicted nitrate diffusion out of biofilm over a 48 h period. After two weeks of no aeration in the established system, nitrification recovered within two days, whereas nitrification establishment in a new system was previously observed to require 20-45 days. These results suggest that once established resident nitrifying microbial communities are quite robust. © 2016 Elsevier Ltd.


Murphy C.,ARM Ltd | Wallace S.,Naturally Wallace Consulting LLC | Knight R.,Heathrow Airport Ltd | Cooper D.,ARM Ltd | Sellers T.,ARM Ltd
Ecological Engineering | Year: 2015

Mayfield Farm Treatment System receives effluent collected from the Southern Catchment of Heathrow Airport, a total of 290ha. During winter operations, weather-related de-icing activity results in large shifts in the flow and concentrations of airport run-off. The biological treatment of spent de-icing fluids is challenging because it involves the treatment of a cold and nutrient-deficient wastewater of variable flow and strength. After a successful full scale trial to determine the efficacy of aerated wetlands, the entire treatment system was upgraded and optimized in 2010. It consisted of a primary reservoir, partial and complete mix zones, a balancing lagoon, and 12 aerated horizontal sub-surface flow (HSSF) treatment wetlands operating in parallel, with a total wetland area of 2.08ha. The original non-aerated HSSF wetland system, commissioned in 2001 had a design cBOD5 loading rate of 374kg/day at a flow rate of 40l/s (Revitt et al., 2001; Richter et al., 2003). The aerated HSSF wetlands now have a design cBOD5 loading rate of 2073kg/day at a maximum flow rate of 80l/s. Due to the weather conditions of the UK, the system is event-driven with highly variable flows and loads, with peak cBOD5 loadings of up to 12,188kg/day.The entire treatment system is now designed to remove 3500kg/day cBOD5 at a design flow of 40l/s. It has a combined capacity of >44,000m3 of wastewater with a retention time of approximately 21 days, depending on the pump flow rate which varies between 40 and 80l/s. Nutrient dosing points have been positioned at strategic points throughout the whole system to prevent nutrient deficiency becoming a limiting factor in the development of a stable and viable mass of bacteria necessary to achieve the design criteria. © 2014 Elsevier B.V.


PubMed | McMaster University, Naturally Wallace Consulting LLC, ARM Ltd, Royal Military College of Canada and Helmholtz Center for Environmental Research
Type: | Journal: Bioresource technology | Year: 2016

In aerated treatment wetlands, oxygen availability is not a limiting factor in sustaining a high level of nitrification in wastewater treatment. In the case of an air blower failure, nitrification would cease, potentially causing adverse effects to the nitrifying bacteria. A field trial was completed investigating nitrification loss when aeration is switched off, and the system recovery rate after the aeration is switched back on. Loss of dissolved oxygen was observed to be more rapid than loss of nitrification. Nitrate was observed in the effluent long after the aeration was switched off (48h+). A complementary modeling study predicted nitrate diffusion out of biofilm over a 48h period. After two weeks of no aeration in the established system, nitrification recovered within two days, whereas nitrification establishment in a new system was previously observed to require 20-45days. These results suggest that once established resident nitrifying microbial communities are quite robust.


Van Oirschot D.,Rietland bvba | Wallace S.,Naturally Wallace Consulting LLC | Van Deun R.,Thomas Moore Kempen
Environmental Science and Pollution Research | Year: 2015

The Badboot (Dutch for swimming pool boat) is a floating swimming pool located in the city center of Antwerp in Belgium. The overall design consists of a recycled ferry boat that serves as a restaurant and next to that a newly built ship that harbours an Olympic size swimming pool, sun decks, locker rooms with showers, and a party space. A major design goal of the project was to make the ship as environmentally friendly as possible. To avoid discharge of contaminated waste water in the Antwerp docks, the ship includes onsite treatment of wastewater in a compact constructed wetland. The treatment wetland system was designed to treat wastewater from visitor locker rooms, showers, toilets, two bars, and the wastewater from the restaurant kitchen. Due to the limited space on board the ship, only 188 m2 could be allocated to a wetland treatment system. As a result, part of the design included intensification of the wetland treatment process through the use of Forced Bed Aeration, which injects small quantities of air in a very uniform grid pattern throughout the wetland with a mechanical air compressor. The system was monitored between August 2012 and March 2013 (with additional sampling in the autumn of 2014). Flows and loads to the wetland were highly variable, but removal efficiency was extremely high; 99.5 % for chemical oxygen demand (COD), 88.6 % for total nitrogen and 97.2 % for ammonia. The treatment performance was assessed using a first-order, tanks-in-series model (the P-k-C* model) and found to be roughly equivalent to similar intensified wetlands operating in Germany. However, treatment performance was substantially better than data reported on passive wetlands, likely as a result of intensification. Even with mechanically assisted aeration, the total oxygen delivered to the treatment wetlands was insufficient to support conventional nitrification and denitrification, so it is likely that alternate nitrogen removal pathways, such as anammox, are operating in the wetland. © 2014, Springer-Verlag Berlin Heidelberg.


Nivala J.,University of Aarhus | Nivala J.,Helmholtz Center for Environmental Research | Headley T.,Bauer Nimr LLC | Wallace S.,Naturally Wallace Consulting LLC | And 4 more authors.
Ecological Engineering | Year: 2013

The Langenreichenbach ecotechnology research facility contains 15 individual pilot-scale treatment systems of eight different designs or operational variants. The designs differ in terms of flow direction, degree of media saturation, media type, loading regime, and aeration mechanism. Seven systems were constructed as planted and unplanted pairs, in order to elucidate the role of common reed (Phragmites australis) in these technologies. The facility is unique in the fact that it is located adjacent to the wastewater treatment plant for the nearby village, enabling all of the pilot-scale systems to receive the same wastewater. The construction of the Langenreichenbach research facility is placed within the overarching discipline of ecological engineering. An overview of the treatment wetland design spectrum (ranging from passive to highly intensified designs) is discussed and the specific designs implemented at Langenreichenbach are presented in detail, along with the internal sampling methods for both saturated and unsaturated systems. © 2013 Elsevier B.V.


Nivala J.,University of Aarhus | Nivala J.,Helmholtz Center for Environmental Research | Wallace S.,Naturally Wallace Consulting LLC | Headley T.,Bauer Nimr LLC | And 5 more authors.
Ecological Engineering | Year: 2013

Subsurface oxygen availability tends to be one of the main rate-limiting factors for removal of carbonaceous and nitrogenous compounds in subsurface flow (SSF) wetlands used for domestic wastewater treatment. This paper reviews the pertinent literature regarding oxygen transfer and consumption in subsurface flow treatment wetlands, and discusses the factors that influence oxygen availability.We also provide first results from a pilot-scale research facility in Langenreichenbach, Germany (15 individual systems of various designs, both with and without plants). Based on the approach given in Kadlec and Wallace (2009), areal-based oxygen consumption rates for horizontal flow systems were estimated to be between 0.5 and 12.9g/m2-d; for vertical flow systems between 7.9 and 58.6g/m2-d; and for intensified systems between 10.9 and 87.5g/m2-d. In general, as the level of intensification increases, so does subsurface oxygen availability. The use of water or air pumps can result in systems with smaller area requirements (and better treatment performance), but it comes at the cost of increased electricity inputs. As the treatment wetland technology envelope expands, so must methods to compare oxygen consumption rates of traditional and intensified SSF treatment wetland designs. © 2012 Elsevier B.V.


Headley T.,Helmholtz Center for Environmental Research | Nivala J.,Helmholtz Center for Environmental Research | Kassa K.,Helmholtz Center for Environmental Research | Olsson L.,University of Aarhus | And 4 more authors.
Ecological Engineering | Year: 2013

Subsurface flow ecotechnologies encompass a range of different designs, varying in terms of flow configuration, media type, energy requirements and use of wetland plants. This study compared the removal rates and internal dynamics of Escherichia coli in a range of commonly used and emerging subsurface flow systems designed for secondary treatment of domestic sewage. Fifteen pilot-scale units were loaded with primary treated sewage in Langenreichenbach, Germany and monitored at the inlet, outlet and a several internal sample points between August 2010 and December 2011. The compared systems spanned a range of energetic intensification levels, including passive horizontal flow (HF) beds (25cm versus 50cm deep), moderately-intensified unsaturated pulse-loaded (12 versus 24 times per day) vertical flow (VF) beds (gravel versus sand media), and highly-intensified beds with aeration (HF versus VF) or reciprocating fill and drain hydraulics. Planted (Phragmites australis) and unplanted forms were compared for all designs except for the reciprocating system (unplanted only). In general, there was no significant effect of vegetation on E. coli removal. Despite receiving the highest loading rates (131-146L/m2d), the aerated HF systems and the reciprocating system achieved the highest log concentration reductions (2.8-4.0log10) and the lowest effluent E. coli concentrations (geometric mean less than 1×104MPN/100mL). The gravel-based VF beds had the lowest log concentration reduction (0.8log10) and highest effluent concentrations (6.4-8.9×105MPN/100mL) at a hydraulic loading rate of 96L/m2d. The design type had an extremely significant effect on areal mass removal rates, with the passive HF beds having the lowest removal rates (50cm depth significantly better than 25cm), followed by the unsaturated VF systems (which were not significantly different from one another), while the aerated and reciprocating systems had the highest removal rates. Within the unsaturated VF beds, the use of sand versus gravel substrate, or hourly versus bi-hourly loading regime in the sand-based systems, had no effect on areal load removal. The internal concentration profiles were not significantly different between the unsaturated VF designs, with the exception of the hourly-loaded, planted bed with sand media which had a more rapid rate of concentration reduction with depth. In the HF beds, the internal E. coli concentration reduction was significantly faster in the aerated beds than in the non-aerated beds. Depth and plants had no significant effect on the internal concentration profiles within the non-aerated HF beds. Within the aerated systems, horizontal-flow achieved better E. coli removal than vertical-flow. Subsurface flow ecotechnologies offer great potential as robust and low-maintenance solutions for reducing the pathogen risk associated with domestic wastewater. The intensified systems produced effluent potentially suitable for restricted surface irrigation, at the cost of higher energy consumption, while the effluent from the other design types would require subsurface irrigation or further disinfection prior to reuse. © 2013 Elsevier B.V.


Boog J.,Helmholtz Center for Environmental Research | Nivala J.,Helmholtz Center for Environmental Research | Aubron T.,Helmholtz Center for Environmental Research | Wallace S.,Naturally Wallace Consulting LLC | And 2 more authors.
Bioresource Technology | Year: 2014

In this study, a side-by-side comparison of two pilot-scale vertical subsurface flow constructed wetlands (6.2m2×0.85m, qi=95L/m2d, τn=3.5d) handling primary treated domestic sewage was conducted. One system (VA-i) was set to intermittent aeration while the other was aerated continuously (VAp-c). Intermittent aeration was provided to VA-i in an 8h on/4h off pattern. The intermittently aerated wetland, VA-i, was observed to have 70% less nitrate nitrogen mass outflow than the continuously aerated wetland, VAp-c. Intermittent aeration was shown to increase treatment performance for TN while saving 33% of running energy cost for aeration. Parallel tracer experiments in the two wetlands showed hydraulic characteristics similar to one Continuously Stirred Tank Reactor (CSTR). Intermittent aeration did not significantly affect the hydraulic functioning of the system. Hydraulic efficiencies were 78% for VAp-c and 76% for VA-i. © 2014 Elsevier Ltd.


PubMed | Naturally Wallace Consulting LLC and Helmholtz Center for Environmental Research
Type: | Journal: Bioresource technology | Year: 2014

In this study, a side-by-side comparison of two pilot-scale vertical subsurface flow constructed wetlands (6.2 m(2)0.85 m, q(i)=95 L/m(2) d, (n)=3.5 d) handling primary treated domestic sewage was conducted. One system (VA-i) was set to intermittent aeration while the other was aerated continuously (VAp-c). Intermittent aeration was provided to VA-i in an 8 h on/4 h off pattern. The intermittently aerated wetland, VA-i, was observed to have 70% less nitrate nitrogen mass outflow than the continuously aerated wetland, VAp-c. Intermittent aeration was shown to increase treatment performance for TN while saving 33% of running energy cost for aeration. Parallel tracer experiments in the two wetlands showed hydraulic characteristics similar to one Continuously Stirred Tank Reactor (CSTR). Intermittent aeration did not significantly affect the hydraulic functioning of the system. Hydraulic efficiencies were 78% for VAp-c and 76% for VA-i.

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