Modelling of temperature effects on removal efficiency and dissolved oxygen concentrations in stormwater ponds

The performance of stormwater ponds, operated under winter conditions, was modelled using the commercial software Mike21 and MOUSE. Direct and indirect effects of changing temperature were investigated. The most important effect of winter conditions is the changed hydrology, characterised by long periods with no runoff followed by snowmelt events with large runoff volumes during several days. This gives lower removal efficiencies than during a period with the same precipitation but without winter conditions. For the concentration of dissolved oxygen, wind is an important factor. Consequently the most important effect of an ice cover on the pond is that it prevents the oxygenation effects of the wind. The direct temperature effects on the removal processes are negligible compared to the indirect effects in changed hydrology and forming of ice cover.

Download Full-text

Simultaneous Nitrification and Denitrification in Biofilm-Electrode Reactor

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.652-654.1633 ◽

2013 ◽

Vol 652-654 ◽

pp. 1633-1636 ◽

Cited By ~ 1

Author(s):

Xiao Liu ◽

Mei Yang ◽

Xian Huai Huang

Keyword(s):

Dissolved Oxygen ◽

Electric Current ◽

Removal Efficiency ◽

Nitrogen Removal ◽

Simultaneous Nitrification And Denitrification ◽

Autotrophic Denitrification ◽

Effluent Recirculation ◽

Removal Efficiencies ◽

Nitrification And Denitrification ◽

Limited Oxygen

To study the nitrification and denitrification in compartmented biofilm-electrode reactor (C-BER) under limited oxygen, influence of mild electrolysis on nitrogen removal was investigated under low C/N (mole ratios) with dissolved oxygen about 1mg/ L. It was found that nitrogen removal was mainly through simultaneous nitrification and denitrification (SND). C/N ratio was 1, average total nitrogen (TN) removal efficiencies were 33% and 45% for electric current of 5 and 15mA. C/N was 0.5, electric current was 25mA and effluent was recirculated, TN removal efficiency increased to 60%, within which autotrophic denitrification accounted for about 51%. There was about 50% NH3-N reduced under 15mA when C/N ratio was 1, this increased to 70% for 25mA when C/N ratio was 0.5. Nevertheless, TN reduced between anode and cathodes accounted for 64% in all. The experimental results show that both higher electric current and effluent recirculation are good for SND process under oxygen-limited condition, nitrogen removal can be activated by mild electrolysis.

Download Full-text

Direct and indirect effects of sea ice cover on major zooplankton groups and planktivorous fishes in the Barents Sea

ICES Journal of Marine Science ◽

10.1093/icesjms/fsz063 ◽

2019 ◽

Vol 76 (Supplement_1) ◽

pp. i24-i36 ◽

Cited By ~ 4

Author(s):

Leif Christian Stige ◽

Elena Eriksen ◽

Padmini Dalpadado ◽

Kotaro Ono

Keyword(s):

Sea Ice ◽

Indirect Effects ◽

Barents Sea ◽

Ice Cover ◽

Arctic Sea Ice ◽

Polar Cod ◽

Direct And Indirect Effects ◽

Top Down ◽

Bottom Up ◽

Delayed Effects

Abstract Reductions in Arctic sea ice affect marine food webs through a multitude of direct and indirect effects. We here analysed direct, indirect, and delayed associations between winter sea ice cover and year-to-year changes in biomasses of the main zooplankton groups (copepods, krill, amphipods) and planktivorous fishes (capelin, polar cod) in the central and northern Barents Sea from 1980 to 2015. Climate effects and species interactions were estimated jointly in a Bayesian state-space model framework. We found that population biomass of capelin increased in years with low sea ice cover, while biomasses of copepods and amphipods decreased. Furthermore, results suggested strong bottom-up effects by krill on capelin and by copepods on amphipods and top-down effects by polar cod on amphipods and by capelin on krill and copepods. Sea ice effects thereby cascaded through the food web through indirect and delayed effects. The indirect and delayed effects amplified the effects of sea ice cover on capelin, copepods and amphipods. For krill, low sea ice cover most likely increased biomass in the short-term but reduced biomass in longer terms because of increased predation pressure. These findings suggest that both bottom-up and top-down processes need to be considered when projecting effects of future climate change on ecosystems.

Download Full-text

Removal of Nitrogen and Phosphorus from Wastewater by Modified Pyrite in a Sequencing Batch Reactor (SBR)

E3S Web of Conferences ◽

10.1051/e3sconf/201913606027 ◽

2019 ◽

Vol 136 ◽

pp. 06027

Author(s):

Hou-Yun Yang ◽

Pei Xu ◽

Hua-Yuan Wang ◽

Wei-Hua Li ◽

Shu-Guang Zhu

Keyword(s):

Removal Efficiency ◽

Phosphorus Removal ◽

Sequencing Batch Reactor ◽

Batch Reactor ◽

Ammonia Nitrogen ◽

Nitrogen And Phosphorus ◽

Nitrogen And Phosphorus Removal ◽

Removal Efficiencies ◽

Removal Processes ◽

Biological Nitrogen

The removal efficiency of nitrogen and phosphorus is challenging in the conventional biological nitrogen and phosphorus removal processes. In this study, the modified pyrite was used as the fillings of se-quencing batch reactor (SBR) in order to improve the efficiencies of nitrogen and phosphorus removal from wastewater. The results showed that SBR with the modified pyrite could significantly improve the removal efficiencies of nitrogen and phosphorus when compared with that in SBR without fillings (control SBR). The average influent ammonia nitrogen (NH4+-N) and total phosphorus (TP) were 6.96±0.17 mg L-1 and 6.94±0.01 mg L-1, respectively. The average NH4+-N and TP removals of modified pyrite constructed SBR were 49.65±19.49% with 3.54±1.31 mg L-1 of average effluent NH4+-N and 76.20±6.55% with 1.84±0.46 mg L-1 of average effluent TP, respectively. While the average NH4+-N and TP removal efficiencies of con-trol SBR were only 34.76±11.28% and 56.28±0.11%. The mechanisms of the SBR with enhanced simulta-neous nitrogen and phosphorus removals might be anaerobic and aerobic oxidations of modified pyrite, and phosphorus retained in the SBR of modified pyrite was mostly in the form of Fe-bound-P.

Download Full-text