Assessment of a Field Tidal Flow Constructed Wetland in Treatment of Swine Wastewater: Life Cycle Approach

A systematic review of life-cycle GHG emissions from intensive pig farming: Accounting and mitigation

Pork accounts for approximately 35 % of the global meat supply, with approximately 747 million tons of CO2e greenhouse gas (GHG) emissions annually. To meet the increasing demand for pork, intensive farming is becoming the priority rearing system owing to its higher productivity. Given the climate transformation ambitions of the pig industry but the lack of knowledge and data, we conducted a systematic review of studies published in the period of 2010-2022 from a life-cycle perspective, with a focus on greenhouse gas emissions accounting and mitigation. The significant variations in systematic harmonized global warming intensities (GWIs) can be primarily attributed to differences in accounting approaches, activity data, technologies and geographical conditions. To understand more, we broke down the entire life cycle and revealed the underlying reasons for modelling mechanisms and data from the main emitters (e.g., feeding, pig rearing, and manure management). These findings are expected to support and improve the transparency, consistency, and comprehensiveness of life-cycle GHG emissions accounting in pig farming. Potential mitigation measures were also reviewed and discussed to provide insights to support the sustainable development of the pig industry.

Screening Life Cycle Environmental Impacts and Assessing Economic Performance of Floating Wetlands for Marine Water Pollution Control

The growing environmental awareness of society, the advancement of nature-based solutions (NbSs), and the need for reliable and cost-effective solutions create a favorable environment of opportunities for floating wetlands as alternative solutions for marine water pollution control. The aim of this work was to screen, through OpenLCA, the environmental impacts of floating wetlands for marine water pollution control at various life cycle stages of the system, and assess its economic performance and contribution to the welfare of society. The stage of raw materials production and acquisition was found to be responsible for the main environmental impacts of the floating wetlands, especially on global warming potential, whereas the main impact of the operational stage was related to the eutrophication potential due to N and P residuals in the effluent. The economic performance indicators of economic net present value (ENPV), economic rate of return (ERR), and benefits/costs ratio (B/C ratio) indicate, although marginally, that floating wetlands may constitute a viable investment with potential positive socioeconomic impacts. However, there are still several scientific challenges and technical issues to be considered for the operational application of such systems at full-scale in marine environments.

Influence of the flooded time on the performance of a tidal flow constructed wetland treating urban stream water

A vertical subsuperficial tidal flow constructed wetland (TFCW) operated under flooded time (FT) variation, was evaluated in the removal of carbonaceous, nitrogenous, and phosphorous matter from urban stream water. The TFCW downflow (117 L) was filled with bricks (44% porosity) and vegetated with Althernanthera philoxeroides (32 plants m^-2). The TFCW was operated under different flooded times - Stage A (48 h), B (36 h), C (24 h), and D (12 h), organic loading rates of 19.58-43.83 gCOD m^-2 d^-1, 3.68-6.94 gTN m^-2 d^-1 and 0.93-2.00 gTP m^-2 d^-1 and volumetric load rates of 46.8, 58.5, 78.0 and 11.7 L d^-1. No significant differences were observed in the removal efficiencies to Chemical Oxygen Demand (COD 66 to 94%), Total Ammonia Nitrogen (TAN 58 to 87%), and Total Nitrogen (TN 53 to 78%) among the stages, and nitrate concentrations lower than 6 mg L^-1 in the effluent. High Total Phosphorus removal was obtained in FT of 48 h (TP 79%). Total phosphorus loading rate was a limiting factor in TP removal, which reduced along with the reduction of FT. The nitrifying community was present over time since ammonia-oxidizing bacteria (Nitrosospira) and nitrite-oxidizing bacteria (Nitrobacter and Nitrospira) were identified in operational stages with variation in relative abundance, but TAN removal efficiency did not show significant differences. There was no change in the denitrifying community structure, indicating that FT did not influence the TN removal. A. philoxeroides was responsible for phytoextraction of 2.1% of TN and 2.7% of TP from the total removed by TFCW. TN removal (65%) was attributed to adsorption in the filtering material and microbial metabolism during the rest time. The findings of this study suggest FT of 12 h to remove COD and TN, and equal to or higher than 48 h to remove TP.

The configuration, purification effect and mechanism of intensified constructed wetland for wastewater treatment from the aspect of nitrogen removal: A review

Constructed wetland (CW) for wastewater treatment has attracted increasing attention. In this review, the system configuration optimization, purification effect and general mechanisms of nitrogen removal in CW are systematically summarized and discussed. Ammonia oxidation is a crucial and primary process for total nitrogen (TN) removal in domestic or livestock wastewater treatment. Aeration, waterdrop influent and tidal operation are three main methods to strengthen the oxygen supplement and nitrification process in CW. Aeration significantly increases the ammonia removal rate (almost 100%), followed by the removal of chemical oxygen demand (COD) and TN. Solid carbon source, iron and anode material can be filled as electron donor for the denitrification process. The co-adjustment of oxygen and carbon/electron donor can form different conditions for different nitrogen removal pathways (e.g. the simultaneous nitrification-denitrification, the partial nitrification-denitrification and the anammox process), and achieve the optimal removal of nitrogen.