Water treatment plant sludge: possibility for soil application

Abstract

The growing demand for drinking water, due to economic and population development, causes an increase in the generation of water treatment plant sludge (WTPS), which is a solid waste Class II A, and should receive an environmentally appropriate destination, according to Brazilian legislation NBR 10004/2004. A sustainable disposal alternative is the application of stake as a substitute to soil, fertilizer or as adsorbent of heavy metals in degraded soils. Aiming to provide parameters for the reuse of WTPS Santa Bárbara, from Pelotas/RS, the waste was characterized physical and chemically and its generation was estimated. From the characterizations, its agronomic potential was analyzed through CONAMA Resolution nº 498/2020, its potential for adsorption of heavy metals, and the possibility of use in waterproofing layer and coverage of landfills. The per capita generation of WTPS Santa Bárbara, with moisture content of 94.96%, was estimated at 315 L hab^-1 year^-1. The heavy metals present in the sludge presented values below the legal advisors, however, the presence of Al and Fe can immobilize the P, nutrient necessary to the plants. The waste showed cation exchange capacity to serve as adsorbent of heavy metals in the remediation of degraded soils, and presented organic matter, macro and micronutrient substances necessary for the development of vegetables. Like landfill layers, the sludge needs to be mixed with other materials with lower permeability coefficients. The recycling of WTPS in agricultural, degraded soils and landfills are promising alternatives to its sustainable management, and reduce its environmental impact.