How short should the SRT be? – Investigation of parallel vs series C- and N-removal processes at the Blue Plains AWTP

The performance of a bench scale upflow sludge bed (USB) denitrifying reactor was evaluated in order to integrate it into a C and N removal system for Sanitary Landfill Leachate. The raw leachate used presented COD and NH4-N average values of 30000 mg/l and 1000 mg/l, respectively. The complete system comprises in addition an UASB reactor and a nitrifying RBC. A portion of the aerobic reactor effluent was recycled into the denitrification stage and some raw leachate was also added as an additional C source. In order to obtain operating parameters the denitrifying reactor was operated alone. Sludge from an aerobic reactor (RBC) treating raw leachate was used as inoculum. Shortly after the start up, good granulation of the sludge bed was observed. Using raw leachate and UASB outlet as carbon sources with COD/NO3-N ratios of 4 and 12, respectively, denitrification efficiencies of about 90% were reached. A sludge yield of 0.16 gVSS/gCODremoved was obtained operating with raw leachate. For the anoxic reactor operating in the complete system, denitrification efficiencies of 90% were also achieved. A nitrogen gas recycle was a successful way to avoid frequently observed sludge bed rising problems.

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Nitrogen removal processes in lakes of different trophic states from on-site measurements and historic data

Aquatic Sciences ◽

10.1007/s00027-021-00795-7 ◽

2021 ◽

Vol 83 (2) ◽

Author(s):

Beat Müller ◽

Raoul Thoma ◽

Kathrin B. L. Baumann ◽

Cameron M. Callbeck ◽

Carsten J. Schubert

Keyword(s):

Eutrophic Lake ◽

Oligotrophic Lake ◽

Removal Rates ◽

N Removal ◽

Central Switzerland ◽

Denitrification Activity ◽

Historic Data ◽

Anthropogenic Nitrogen ◽

Removal Processes ◽

Sediment Interface

AbstractFreshwater lakes are essential hotspots for the removal of excessive anthropogenic nitrogen (N) loads transported from the land to coastal oceans. The biogeochemical processes responsible for N removal, the corresponding transformation rates and overall removal efficiencies differ between lakes, however, it is unclear what the main controlling factors are. Here, we investigated the factors that moderate the rates of N removal under contrasting trophic states in two lakes located in central Switzerland. In the eutrophic Lake Baldegg and the oligotrophic Lake Sarnen, we specifically examined seasonal sediment porewater chemistry, organic matter sedimentation rates, as well as 33-year of historic water column data. We find that the eutrophic Lake Baldegg, which contributed to the removal of 20 ± 6.6 gN m−2 year−1, effectively removed two-thirds of the total areal N load. In stark contrast, the more oligotrophic Lake Sarnen contributed to 3.2 ± 4.2 gN m−2 year−1, and had removed only one-third of the areal N load. The historic dataset of the eutrophic lake revealed a close linkage between annual loads of dissolved N (DN) and removal rates (NRR = 0.63 × DN load) and a significant correlation of the concentration of bottom water nitrate and removal rates. We further show that the seasonal increase in N removal rates of the eutrophic lake correlated significantly with seasonal oxygen fluxes measured across the water–sediment interface (R2 = 0.75). We suggest that increasing oxygen enhances sediment mineralization and stimulates nitrification, indirectly enhancing denitrification activity.

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Prediction of dissolved inorganic nitrogen (DIN) concentrations in deep, seasonally stratified lakes based on rates of DIN input and N removal processes

Aquatic Sciences ◽

10.1007/bf00877440 ◽

1993 ◽

Vol 55 (2) ◽

pp. 112-131 ◽

Cited By ~ 10

Author(s):

P. H�hener ◽

R. G�chter

Keyword(s):

Inorganic Nitrogen ◽

Dissolved Inorganic Nitrogen ◽

Stratified Lakes ◽

N Removal ◽

Removal Processes

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Carbon and nitrogen dynamics and greenhouse gas emissions in constructed wetlands treating wastewater: a review

Hydrology and Earth System Sciences ◽

10.5194/hess-20-109-2016 ◽

2016 ◽

Vol 20 (1) ◽

pp. 109-123 ◽

Cited By ~ 31

Author(s):

M. M. R. Jahangir ◽

K. G. Richards ◽

M. G. Healy ◽

L. Gill ◽

C. Müller ◽

...

Keyword(s):

Greenhouse Gas ◽

Empirical Evidence ◽

Constructed Wetlands ◽

Nutrient Removal ◽

Management Practices ◽

N2o Emissions ◽

Knowledge Gaps ◽

Ch4 Emissions ◽

N Removal ◽

C And N

Abstract. The removal efficiency of carbon (C) and nitrogen (N) in constructed wetlands (CWs) is very inconsistent and frequently does not reveal whether the removal processes are due to physical attenuation or whether the different species have been transformed to other reactive forms. Previous research on nutrient removal in CWs did not consider the dynamics of pollution swapping (the increase of one pollutant as a result of a measure introduced to reduce a different pollutant) driven by transformational processes within and around the system. This paper aims to address this knowledge gap by reviewing the biogeochemical dynamics and fate of C and N in CWs and their potential impact on the environment, and by presenting novel ways in which these knowledge gaps may be eliminated. Nutrient removal in CWs varies with the type of CW, vegetation, climate, season, geographical region, and management practices. Horizontal flow CWs tend to have good nitrate (NO3−) removal, as they provide good conditions for denitrification, but cannot remove ammonium (NH4+) due to limited ability to nitrify NH4+. Vertical flow CWs have good NH4+ removal, but their denitrification ability is low. Surface flow CWs decrease nitrous oxide (N2O) emissions but increase methane (CH4) emissions; subsurface flow CWs increase N2O and carbon dioxide (CO2) emissions, but decrease CH4 emissions. Mixed species of vegetation perform better than monocultures in increasing C and N removal and decreasing greenhouse gas (GHG) emissions, but empirical evidence is still scarce. Lower hydraulic loadings with higher hydraulic retention times enhance nutrient removal, but more empirical evidence is required to determine an optimum design. A conceptual model highlighting the current state of knowledge is presented and experimental work that should be undertaken to address knowledge gaps across CWs, vegetation and wastewater types, hydraulic loading rates and regimes, and retention times, is suggested. We recommend that further research on process-based C and N removal and on the balancing of end products into reactive and benign forms is critical to the assessment of the environmental performance of CWs.

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Impacts of willow and miscanthus bioenergy buffers on biogeochemical N removal processes along the soil-groundwater continuum

GCB Bioenergy ◽

10.1111/gcbb.12340 ◽

2016 ◽

Vol 9 (1) ◽

pp. 246-261 ◽

Cited By ~ 19

Author(s):

Andrea Ferrarini ◽

Flavio Fornasier ◽

Paolo Serra ◽

Federico Ferrari ◽

Marco Trevisan ◽

...

Keyword(s):

N Removal ◽

Removal Processes

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Carbon and nitrogen dynamics and greenhouse gases emissions in constructed wetlands: a review

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-11-7615-2014 ◽

2014 ◽

Vol 11 (7) ◽

pp. 7615-7657 ◽

Cited By ~ 2

Author(s):

M. M. R. Jahangir ◽

O. Fenton ◽

L. Gill ◽

C. Müller ◽

P. Johnston ◽

...

Keyword(s):

Constructed Wetlands ◽

Surface Waters ◽

Current Knowledge ◽

Sustainable Use ◽

Transformation Products ◽

Detailed Examination ◽

Dissolved Carbon ◽

N Removal ◽

Carbon And Nitrogen Dynamics ◽

C And N

Abstract. The nitrogen (N) removal efficiency of constructed wetlands (CWs) is very inconsistent and does not alone explain if the removed species are reduced by physical attenuation or if they are transformed to other reactive forms (pollution swapping). There are many pathways for the removed N to remain in the system: accumulation in the sediments, leaching to groundwater (nitrate-NO3- and ammonium-NH4+), emission to atmosphere via nitrous oxide- N2O and ammonia and/or conversion to N2 gas and adsorption to sediments. The kinetics of these pathways/processes varies with CWs management and therefore needs to be studied quantitatively for the sustainable use of CWs. For example, the quality of groundwater underlying CWs with regards to the reactive N (Nr) species is largely unknown. Equally, there is a dearth of information on the extent of Nr accumulation in soils and discharge to surface waters and air. Moreover, CWs are rich in dissolved organic carbon (DOC) and produce substantial amounts of CO2 and CH4. These dissolved carbon (C) species drain out to ground and surface waters and emit to the atmosphere. The dynamics of dissolved N2O, CO2 and CH4 in CWs is a key "missing piece" in our understanding of global greenhouse gas budgets. In this review we provide an overview of the current knowledge and discussion about the dynamics of C and N in CWs and their likely impacts on aquatic and atmospheric environments. We suggest that the fate of various N species in CWs and their surface emissions and subsurface drainage fluxes need to be evaluated in a holistic way to better understand their potential for pollution swapping. Research on the process based N removal and balancing the end products into reactive and benign forms are critical to assess environmental impacts of CWs. Thus we strongly suggest that in situ N transformation and fate of the transformation products with regards to pollution swapping requires further detailed examination.

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Ammonium and nitrate removal in vegetated and unvegetated gravel bed microcosm wetlands

Water Science & Technology ◽

10.2166/wst.1995.0144 ◽

1995 ◽

Vol 32 (3) ◽

pp. 219-228 ◽

Cited By ~ 19

Author(s):

Zhu Tong ◽

F. J. Sikora

Keyword(s):

Root Biomass ◽

Plant Biomass ◽

N Uptake ◽

Nitrate Removal ◽

Solution Chemistry ◽

Batch Mode ◽

Organic C ◽

N Removal ◽

Removal Processes ◽

Nutrient Solutions

A greenhouse experiment was conducted at Tennessee Valley Authority, Alabama, USA, in the summer of 1993 to investigate ammonium and nitrate removal processes in constructed wetlands. Microcosm wetlands cells were used in the study and consisted of plastic containers with 0.4 × 0.35 m2 surface area and 0.5 m depth. Two separate experiments were conducted. One experiment analyzed NH4-N removal and the other analyzed NO3-N removal. Nutrient solutions containing approximately 48 mg/l NH4-N or NO3-N were added in a batch mode to the wetland microcosms and the solution chemistry was analyzed with time. Treatments consisted of unplanted cells or cells planted with canarygrass (Phalaris arundinacea), reed (Phragmites communis), bulrush (Scirpus atrovirens georgianus) or typha (Typha latifolia). Another treatment consisted of added nutrient solutions containing or not containing C at 112 mg/l. In the NH4-N removal experiment, the rate of NH4-N removal occurred in the order: reed > canarygrass = bulrush > typha ≫ unplanted in wetland cells with and without C. The order of NH4-N removal was believed to be associated with the density of root biomass in the gravel. The greater the root biomass, the greater the chance for plant N uptake or nitrification mediated by O2 transport to the rhizosphere. In the NO3-N experiment, the rate of NO3-N removal occurred in the order: reed = canarygrass > typha = bulrush > unplanted cells. Labelled K15NO3 was used to trace the NO3-N removal process. By measuring the 15N in the plant biomass, the quantity of NO3-N removed via plant uptake was delineated from combined removal processes of denitrification and immobilization. In the treatments with C, 55 to 70% of the NO3-N was removed via denitrification and immobilzation. For bulrush, reed and typha, the quantity of NO3-N removed via denitrification and immobilization without added C was reduced to 14 to 30%. However, NO3-N removal via denitrification and immobilization remained high at 72% of added NO3-N in canarygrass cells due to high concentrations of organic C released from the canarygrass roots (15-20 mg/l C) that apparently did not limit denitrification or immobilization.

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Combination of photo-Fenton and biological SBBR processes for sulfamethoxazole remediation

Water Science & Technology ◽

10.2166/wst.2008.532 ◽

2008 ◽

Vol 58 (9) ◽

pp. 1707-1713 ◽

Cited By ~ 3

Author(s):

O. González ◽

M. Esplugas ◽

C. Sans ◽

S. Esplugas

Keyword(s):

Biological Treatment ◽

Fenton Reaction ◽

Biofilm Reactor ◽

Synthetic Wastewater ◽

Total N ◽

Sequencing Batch Biofilm Reactor ◽

N Removal ◽

Start Up ◽

C And N ◽

Combined Strategy

A combined strategy of a photo-Fenton pretreatment followed by a Sequencing Batch Biofilm Reactor (SBBR) was evaluated for total C and N removal from a synthetic wastewater containing 200 mg L−1 of the antibiotic Sulfamethoxazole (SMX). Photo-Fenton reaction was performed with two different H2O2 concentrations (300 and 400 mg L−1) and 10 mg L−1 of Fe2 + . The pre-treated effluents with the antibiotic intermediates as sole carbon source, together with a nutrients solution, were used as feed for the biological reactor. The SBBR was operated under aerobic conditions to mineralize the organic carbon and the hydraulic retention time (HRT) was optimized down to 8 hours. Then, an anoxic denitrification stage of 24 hours of HRT was added right after the aerobic stage of the same duration in order to remove the NO3− generated along the chemical–biological treatment. TOC, COD and SMX concentrations together with O2 uptake rate (OUR) profiles were monitored in purpose of assessing the performance of the system. NO3−, NH4+ and total N concentrations were analyzed to find out the fate of N contained in the initial SMX molecule. A start up strategy resulted in the correct formation of a biofilm over the volcanic support. The total TOC removals achieved with the combination of the chemical and the biological processes were 75.7 and 87.7% for the low and the high H2O2 concentration pretreatments respectively. Practically all N present in the SMX solution was eliminated in the SBBR when the aerobic–anoxic strategy was used.

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