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

Abstract

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 the development of 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 lack of resources and logistical hardships make 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 bellow 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, under different reaction pHs and using mechanical agitation, were tested to access their organic matter removal efficiency, as chemical oxygen demand (COD). The best 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%).

Keywords

• urban wastewater
• antarctica
• chemical precipitation
• co2 capture
• hydroponics