Lodo de Estação de Tratamento de Água como substrato de formação de mudas e na fitorremediação de cobre por Ipê-de-jardim

Abstract

The demand for high-quality water is increasing, which places growing pressure on the operation of water treatment plants (WTPs). During the production of drinking water, Water Treatment Plant Sludge (WTS) is generated. The most common disposal practices for this solid waste include deposition in sanitary landfills, discharge into sewage systems, or even direct release into water bodies. Due to its potential environmental impact, the study and development of appropriate management and disposal methods for this sludge are crucial. In this context, the present study aimed to evaluate the use of sludge from the Capim Branco Water Treatment Plant, located in Uberlândia, Minas Gerais, Brazil, as a substrate for seedling growth and its capacity to promote phytoremediation by Tecoma stans (L.) Juss. ex Kunth (yellow trumpetbush) in copper-contaminated soils. In the first experiment, five treatments with different sludge concentrations (0%, 12.5%, 25%, 50%, and 75%) were established for seedling growth. The 25% sludge treatment promoted increases in plant height, fresh shoot mass (FSM), fresh root mass (FRM), and dry root mass (DRM), and reduced the percentage loss from fresh to dry mass after drying. Based on these results, this concentration was selected for a subsequent experiment conducted in copper-contaminated soil to assess the phytoremediation potential of yellow trumpetbush combined with the application of WTP sludge. In the second experiment, six treatments with different combinations were evaluated: M1, growth of yellow trumpetbush in uncontaminated soil; M2, yellow trumpetbush grown in soil with WTS addition; M3, yellow trumpetbush grown in copper-contaminated soil; M4, yellow trumpetbush grown in copper-contaminated soil with WTS addition; M5, copper-contaminated soil without plant growth; and M6, copper-contaminated soil with WTS addition and without plant growth. Seedlings germinated in a commercial substrate were transplanted into pots containing the respective treatments and cultivated for 75 days. Treatments without sludge addition (M1 and M3) showed greater copper uptake by the plants, indicating that WTS may hinder the phytoremediation process. However, treatments containing sludge (M2, M4, and M6) showed improvements in soil chemical properties, including increased pH and sum of exchangeable bases, indicating potential enhancement of soil fertility.