A review on the main affecting factors of greenhouse gases emission in constructed wetlands

Greenhouse gas emission in constructed wetlands for wastewater treatment: A review

비점오염원 저감을 위해 설치된 주암호 생태습지의 수질정화효율을 평가하기 위하여 시스템별 및 시기별 오염물질의 함량과 처리효율을 조사하였다. 유입원수의 BOD, COD, SS, T-N 및 T-P의 함량은 각각 0.20~0.91, 1.24~8.00, 0.6~8.6, 0.04~2.50 및 <TEX>$0.001{\sim}0.685mg\;L^{-1}$</TEX> 범위로 나타났다. 주암호 생태습지 유입수의 대부분이 현행 오염물질 수질기준을 초과하지 않은 상태로 유입되었지만 비점오염원이 많이 유입되는 특정 시기 (장마철)에는 높은 오염물질 함량을 나타내었다. 시기별로는 전반적으로 여름철에 유입원수의 영양염류의 유입이 다른 시기에 비해 높은 경향이었다. 전반적으로 C 시스템이 오염물질의 처리효율이 가장 높은 경향이었다. A 시스템의 습지들은 대부분 겨풀이 우점하고 있었으며 B 시스템의 습지들은 겨풀과 연꽃이 우점하고 있었다. C 시스템의 습지들은 겨풀, 수련 및 부들이 우점하고 있었다. 주암호 생태습지는 오염물질의 처리능이 전반적으로 안정화 상태에 도달하지 못한 것으로 판단되며, 특히 겨풀 및 물 참새피 등 식물교란종의 습지 내 침투로 인하여 습지의 수질정화효율이 전반적으로 낮았다. 따라서 본 연구결과로부터 조성초기 인공습지는 식생의 발달 여부가 수질의 안정화와 습지의 수생태학적 역할을 증대시키는데 중요한 역할을 하는 것으로 판단된다. To reduce non-point source pollutants in Juam Lake eco-wetlands, purification efficiencies of pollutants were investigated at three different systems. The constructed wetlands (CWs) consisted of A system, B system and C system. A system consisted of <TEX>$1^{st}$</TEX> free water surface (FWS) CW, <TEX>$2^{nd}$</TEX> FWS CW, <TEX>$3^{rd}$</TEX> FWS CW, <TEX>$4^{th}$</TEX> subsurface flow (SSF) CW and <TEX>$5^{th}$</TEX> SSF CW. B system consisted of <TEX>$1^{st}$</TEX> FWS CW, <TEX>$2^{nd}$</TEX> FWS CW, <TEX>$3^{rd}$</TEX> FWS CW, <TEX>$4^{th}$</TEX> FWS CW and <TEX>$5^{th}$</TEX> SSF CW. C system consisted of <TEX>$1^{st}$</TEX> FWS CW, <TEX>$2^{nd}$</TEX> FWS CW, <TEX>$3^{rd}$</TEX> FWS CW, <TEX>$4^{th}$</TEX> FWS CW and <TEX>$5^{th}$</TEX> SSF CW. The concentrations of BOD, COD, SS, T-N and T-P in inflow ranged 0.20 ~ 0.91, 1.24 ~ 8.00, 0.60 ~ 8.60, 0.04 ~ 2.50 and <TEX>$0.001{\sim}0.685mg\;L^{-1}$</TEX> from March to October in 2011, respectively. Removal rates of BOD, SS, T-N and T-P were high in Autumn, Spring, Spring and Summer, respectively. In A system, <TEX>$1^{st}$</TEX> FWS CW, <TEX>$2^{nd}$</TEX> FWS CW and <TEX>$3^{rd}$</TEX> FWS CW were dominated by Leersia oryzoides. In B system, <TEX>$1^{st}$</TEX> FWS CW, <TEX>$3^{rd}$</TEX> FWS CW and <TEX>$4^{th}$</TEX> FWS CW were dominated by Leersia oryzoides. In C system, <TEX>$2^{nd}$</TEX> FWS CW and <TEX>$3^{rd}$</TEX> FWS CW were dominated by Nymphaea teragona.

Long-term performance of an integrated constructed wetland for advanced treatment of mixed wastewater

The effect of pre-aeration on the purification processes in the long-term performance of a horizontal subsurface flow constructed wetland

Adding Corbicula fluminea altered the effect of plant species diversity on greenhouse gas emissions and nitrogen removal from constructed wetlands in the low-temperature season

Climate regulation by free water surface constructed wetlands for wastewater treatment and created riverine wetlands

Effects of biochar and N-stabilizers on greenhouse gas emissions from a subtropical pasture field applied with organic and inorganic nitrogen fertilizers

Ibuprofen and diclofenac, two commonly used pharmaceuticals, were studied to evaluate the removal behavior of acid pharmaceuticals in constructed wetlands (CWs) with different flow types, vegetation and seasons. It was shown that flow types influenced the results significantly. The average removal efficiency of ibuprofen in horizontal subsurface flow (HSSF) and vertical subsurface flow (VSSF) CWs (69% and 60%, respectively) was significantly higher than that in surface flow (SF) CWs (26%). For diclofenac, SF CWs (58%) was significantly higher than HSSF and VSSF CWs (49% and 43%, respectively). In addition, the presence of plants improved the efficiency of ibuprofen, while it had no significant influence on the removal of diclofenac. Paired t-test found out that summer and autumn season variety had little impact on the removal. Furthermore, the removal of diclofenac and DO, as well as COD, showed very significant negative correlations. Opposite to diclofenac, the removal of ibuprofen had good positive correlations with dehydrogenase activities. The research indicated that aerobic biodegradation behavior mainly took place in ibuprofen, yet anaerobic biodegradation and photolysis behavior were expected for diclofenac.

Azolla, a common aquatic fern has been used successfully as a dual crop with lowland rice. It grows rapidly and fixes atmospheric nitrogen for rice paddy. However, its ecological significance especially on greenhouse gases emissions remains unclear. Three independent experiments -two pot (2016 and 2017), and one field in 2019- were conducted to investigate the effects Azolla (A. filiculoides Lam.) either or both as dual cropping and green manure along with rice plant on simultaneous methane (CH4) and nitrous oxide (N2O) emissions from constantly flooded paddy soil. Under pot setups, dual cropping Azolla as a cover with rice plant significantly decreased seasonal CH4 emission by 34.7%, with no effect on N2O emissions. Suppressed CH4 emission was likely due to an increase in dissolved oxygen concentration and redox potential at the soil-water interface simulating CH4 oxidation. However, incorporation of Azolla as green manure into the soil plus dual crop in conjunction with chemical fertilizers significantly increased CH4 emission by 37.5% but decreased N2O emission by 74.5%. The significantly higher CH4 and lower N2O emissions were attributed to the readily decomposable incorporated Azolla, acting both as a source of CH4 production and N2O reduction. Contrary to the pot observations, application of Azolla as a dual crop in conjunction with chemical fertilizer or incorporated as green manure plus dual cropping in the field did not significantly affect seasonal CH4 emissions, but significantly increased cumulative N2O emissions at the middle rice growth stages by 645%&amp;#8212;816%, and the total seasonal emission 3.4-fold. The higher N2O emissions were partly attributed to large quantities of exogenous organic carbon resulting from the accelerated growth and subsequent senescence of Azolla cover applied as a dual crop as impacted by higher summer air temperatures. Our observations suggest that dual cropping of Azolla with rice has the potential to reduce CH4 emissions from flooded rice paddies. Conversely, incorporation of Azolla as green manure into the paddy soil plus dual cropping in conjunction with or without chemical fertilizers indicates an inconsistent relationship between CH4 and N2O emissions. Long-term studies are needed to evaluate the relationship between leguminous cover crops and their effects on factors influencing CH4 and N2O emissions from continuously flooded rice paddies.

Greenhouse gas emission from direct seeding paddy field under different rice tillage systems in central China

Field measurements were made from June 2001 to May 2002 to evaluate the effect of crop residue application and temperature on CO2, CH4, and N2O emissions within an entire rice-wheat rotation season. Rapeseed cake and wheat straw were incorporated into the soil at a rate of 2.25 t hm−2 when the rice crop was transplanted in June 2001. Compared with the control, the incorporation of rapeseed cake enhanced the emissions of CO2, CH4, and N2O in the rice-growing season by 12.3%, 252.3%, and 17.5%, respectively, while no further effect was held on the emissions of CO2 and N2O in the following wheatgrowing season. The incorporation of wheat straw enhanced the emissions of CO2 and CH4 by 7.1% and 249.6%, respectively, but reduced the N2O emission by 18.8% in the rice-growing season. Significant reductions of 17.8% for the CO2 and of 12.9% for the N2O emission were observed in the following wheatgrowing season. A positive correlation existed between the emissions of N2O and CO2 (R 2 = 0.445,n = 73,p < 0.001) from the rice-growing season when N2O was emitted. A trade-off relationship between the emissions of CH4 and N2O was found in the rice-growing season. The CH4 emission was significantly correlated with the CO2 emission for the period from rice transplantation to field drainage, but not for the entire rice-growing season. In addition, air temperature was found to regulate the CO2 emissions from the non-waterlogged period over the entire rice-wheat rotation season and the N2O emissions from the nonwaterlogged period of the rice-growing season, which can be quantitatively described by an exponential function. The temperature coefficient (Q 10) was then evaluated to be 2.3±0.2 for the CO2 emission and 3.9±0.4 for the N2O emission, respectively.

Application of constructed wetlands for wastewater treatment in tropical and subtropical regions (2000–2013)

This study investigates the effect of energy consumption on greenhouse gas (GHG) emissions in 33 African countries from 1995–2017. It contributes to the literature by investigating the effect of disaggregated measures of energy consumption (coal, oil and other liquids, renewable energy, and electricity) on GHG emissions (CO2, N2O, CH4, and total GHG emissions) in Africa and identifies the transmission channels through which energy consumption affects GHG emissions. The system GMM is used in the study as it accounts for possible endogeneity and the potential correlation between the error term and the country fixed effects. The results show that coal consumption significantly increases CO2, CH4, and total GHG emissions and reduces N2O emissions. Oil consumption increases CO2 and total GHG emissions but reduces N2O and CH4 emissions. Renewable energy consumption reduces CO2 and CH4 emissions but increases N2O emissions. Finally, electricity consumption promotes CO2, N2O, CH4 and total GHG emissions in Africa. Further analyses show that foreign trade and economic growth are the channels through which oil consumption increases GHG emissions. The adverse effect of electricity is through urbanization. Renewable consumption could decrease GHG emissions through sustainable urbanization and trade policies. The findings suggest that countries should gradually reduce coal consumption and encourage renewable energy consumption, which has the lowest impact on the environment.

The influence of incorporating microbial fuel cells on greenhouse gas emissions from constructed wetlands

Evaluating the sustainability of free water surface flow constructed wetlands: Methane and nitrous oxide emissions