WTP and WWTP sludge management: a case study in the metropolitan area of Campinas, southeastern Brazil

Disposal of sludges generated at water treatment plants (WTPs) and wastewater treatment plants (WWTPs) located in highly urbanized regions challenges water industry. Legal restrictions based on public health and sustainability push managers forward in order to find beneficial use markets rather than deficit and high-cost landfilling. A GIS-based linear optimization method for sludge management was firstly proposed. The metropolitan area of Campinas belongs to the watershed of the rivers Piracicaba, Capivari, and Jundiaí (PCJ), which comprises 76 municipalities, representing over 5 million urban consumers, supplied by 100 WTPs and 116 WWTPs. An assessment of soils feasibility for WWTP sludge reception was carried out. The beneficial uses assumed to be the best for WTP and WWTP sludges were, respectively, addition in the industrial process of ceramic bricks manufacture, and application on sugarcane crop areas for ethanol production. Three scenarios were set for sludges from WTPs and also for WWTPs. Those scenarios represented maximum, intermediate, and minimum reception capability for each reception location or area. Ceramic industries located within PCJ watershed showed to be capable of receptioning the total amount of WTP sludges, if a minimum 2% mass/mass replacement of raw materials (mainly clay) is provided. There are plenty of feasible areas for WWTP sludge application; thus, sludge agronomic quality and farmers' acceptance constitute the only steps to climb. This paper brings an innovative tool regarding sludge management which may be useful to decision-makers, especially wherever several sources and reception areas are playing on game board. The proposed method can be applied at different locations and for other sludge uses.