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Raleigh, NC, United States

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. Source


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. Source


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. Source


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. Source


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. Source

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