SOILS AS NATURAL REACTORS FOR SWINE WASTEWATER TREATMENT

Abstract

The ability of soils to mineralize organic matter depends on their individual characteristics; when waste waters are added to them their organic matter content (OM), cationic exchange capacity (CEC) and percentage of clay (PC) are altered. Pedotransfer functions (PTF) enable certain processes to be determined from easily measured soil properties. The aims of this study were i) to generate PTF to estimate the retention and mineralisation of dissolved organic matter (DOM) present in swine wastewater (SWW) based on measurements of OM, CEC and PC and ii) to identify the soils most suited to acting as natural reactors for treating SWW, using multicriteria analysis. Samples were taken from ten soils (epipedons or superficial samples) to measure the retention of dissolved organic matter (RDOM) in 30 cm high soil columns, making three applications of SWW. In addition, an experiment was carried out in pots to measure the effect of SWW on soil carbon evolution (SCE) and the potential anaerobic nitrogen mineralisation (PANM). Multiple regressions were made using soil OM (%), CEC (cmol+ kg-1) and PC (%) as independent variables and Chemical Oxygen Demand (COD), SCE and PANM as dependent variables. The PFT found were RDOM = 41.5 + (2.8*CEC) – (0.81*PC) – (3.5*OM)  r= 0.81; SCE =  542.3 + (20.1*OM) + (4.6*CEC) – (2.7*PC) r= 0.96; PANM = -8.4 + (3.45*OM) + (1.12*PC) – (2.20*CEC) r= 0.88. The most suitable soils for acting as natural reactors of SWW were the Luvisol LVct and an unclassified EPI-1.