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An Eco-Innovative Solution for Reuse of Leachate Chemical Precipitation Sludge: Application to Sanitary Landfill Coverage

Martínez-Cruz Alfredo, Fernandes Annabel, Ramos Filomena, Soares Sofia, Correia Pedro, Baía Ana, Lopes Ana, Carvalho Fátima

Ecological Engineering & Environmental Technology

2021

Vol. 22, iss. 2

52--58

Sanitary landfill leachate was treated by chemical precipitation and the potential use of mixtures of the chemical precipitation sludge (CPS) generated and natural soil to cover the solid waste at sanitary landfills was evaluated. Tests were performed with soils having 0, 5 and 10% CPS, and the organic matter, pH, compaction, hydraulic conductivity, particle-size, liquid limit, plastic limit, and plasticity index were determined. It was found that leaching increased with CPS concentration, as well as the fine particles content in the soil, which reduced the hydraulic conductivity. pH was the most affected parameter, with values of 7.03, 7.12, and 11.46 for 0, 5 and 10% CPS, respectively. However, at 5% CPS, biodegradability was favored without a significant increase in the leaching process, showing that CPS can be used as temporary cover material, without adversely affecting the landfill system, being an eco-innovative solution for the final disposal of the sludge.

Manual Treatment of Urban Wastewater by Chemical Precipitation for Production of Hydroponic Nutrient Solutions

Correia Tânia, Regato Mariana, Almeida Adelaide, Santos Teresa, Amaral Leonor, Carvalho Fátima

Journal of Ecological Engineering

2020

Vol. 21, nr 3

143--152

An urban wastewater treatment system was developed in Portugal for posterior in situ feasibility testing at the Bulgarian Antarctic Base, using its domestic wastewater. The aim of this system was to develop a low cost, integrated approach for wastewater treatment and production of nutrient solutions (NS) for hydroponic cultivation of lettuce (Lactuca sativa var. crispa) in Antarctic stations, or any other place where the lack of resources and logistical hardships make the wastewater treatment and reuse impractical. The wastewater treatment system consisted in manual agitation lime chemical precipitation (LCPm) and effluent natural neutralization (NN) by atmospheric CO2 carbonation reactions (with and without air injection). The resulting effluent/NS had macronutrient values (nitrogen and phosphorous) for the hydroponic cultivation of lettuce below the values of commercial NS and a high pH (pH ≈ 8). The treatment achieved a total coliform removal rate of 100%. Before the LCPm treatment system development, several lime-based reagents were tested under different reaction pH and using mechanical agitation, to access their organic matter removal efficiency, as chemical oxygen demand (COD). The best COD removal results obtained were: commercial Ca(OH)2 (pH 11.5 – 89%), reagent grade Ca(OH)2 (pH 11.5 – 79%) and CaO (pH 12.0 – 64%).