Nitrogen removal on recycling water process of wastewater treatment plant effluent using subsurface horizontal wetland with continuous feed

Evaluation of irrigation suitability potential of brewery effluent post treated in a pilot horizontal subsurface flow constructed wetland system: implications for sustainable urban agriculture

The use of untreated or partially treated wastewater reuse for urban and peri-urban agricultural irrigation is a common practice in developing countries like Ethiopia. Such practices, however, pose significant environmental and public health risks. The objective of this study was to evaluate the irrigation suitability of anaerobic digestion brewery effluent (ADBE) and two-stage horizontal subsurface constructed wetland post-treated ADBE (CWPBE). A series of pot experiments were conducted in a plastic - greenhouse system arranged in three sets of irrigation schemes: Treatment Group1 (TG1): municipal pipe tap water (MPTW) irrigated pots; Treatment Group2 (TG2): ADBE irrigated pots, and Treatment Group3 (TG3): CWPBE irrigated pots. Pots packed with the same amount of sandy clay loam soil and local tomato seeds sown were irrigated following an updated tomato irrigation schedule derived from the FAO CROPWAT stimulation model for 120 days. The findings from key irrigation water quality parameters showed that the CWPBE achieved the prescribed irrigation water standards with values of pH (7.4 ± 0.15), electrical conductivity (1.9 ± 0.11 dS.m^-1), total suspended solids (25 ± 4.17 mgL^-1), chemical oxygen demand (185.1 ± 1.66 mgL^-1), total nitrogen (17.4 ± 0.7 mgL^-1), total phosphorous (8.8 ± 0.26 mgkg^-1), calcium (10.5 ± 3.6 mgkg^-1), magnesium (4.9 ± 0.98 mgkg^-1), sodium (4.4 ± 1.51 mgkg^-1), potassium (2.3 ± 1.15 mgkg^-1), sodium adsorption ratio (1.6 ± 0.34), and total coliform (8 ± 0.16×10^-5 CFU/100 mL). Moreover, tomato plants grown in TG3 attained higher growth such as number of leaves (85.6 ± 4.68), plant height (92.2 ± 1.29 cm), stem diameter (13.1 ± 2.35 cm) and leaf area (35.5 ± 1.03 cm²) as well as higher biomass (61.2 ± 1.33 kgm^-2) and fruit (46.4 ± 3.51 kgm^-2) yields over other treatment groups. The results revealed that irrigation waters significantly improved both growth and yield parameters of tomato plants with the ascending order of TG1 < TG2 < TG3. Moreover, CWPBE showed minima short-term residual effect on soil physicochemical properties as compared to ADBE, and thus, it has potential suitability for agricultural irrigation reuse.

High biomass yield increases in a primary effluent wastewater phytofiltration are associated to altered leaf morphology and stomatal size in Salix miyabeana

Municipal wastewater treatment using willow 'phyto'-filtration has the potential for reduced environmental impact compared to conventional treatment practices. However, the physiological adaptations underpinning tolerance to high wastewater irrigation in willow are unknown. A one-hectare phytofiltration plantation established using the Salix miyabeana cultivar 'SX67' in Saint-Roch-de-l'Achigan, Quebec, Canada, tested the impact of unirrigated, potable water or two loads of primary effluent wastewater 19 and 30 ML ha^-1 yr^-1. A nitrogen load of 817 kg N ha^-1 from wastewater did not increase soil pore water nitrogen concentrations beyond Quebec drinking water standards. The willow phytofiltration phenotype had increased leaf area (+106-142%) and leaf nitrogen (+94%) which were accompanied by significant increases in chlorophyll a + b content. Wastewater irrigated trees had higher stomatal sizes and a higher stomatal pore index, despite lower stomatal density, resulting in increased stomatal conductance (+42-78%). These developmental responses led to substantial increases in biomass yields of 56-207% and potable water controls revealed the nitrogen load to be necessary for the high productivity of 28-40 t ha^-1 yr^-1 in wastewater irrigated trees. Collectively, this study suggests phytofiltration plantations could treat primary effluent municipal wastewater at volumes of at least 19 million litres per hectare and benefit from increased yields of sustainable biomass over a two-year coppice cycle. Added-value cultivation practices, such as phytofiltration, have the potential to mitigate negative local and global environmental impact of wastewater treatment while providing valuable services and sustainable bioproducts.