In Madeira, the vast majority of Wastewater Treatment Plants (WWTP) operate only with primary treatment, an essentially physical and mechanical process that is limited to removing coarse solids, sand, grease and part of the suspended matter through sedimentation. Unlike more advanced systems, this elementary level of treatment does not include the secondary stage (a biological process that uses microorganisms to degrade dissolved organic matter) nor the tertiary stage (which applies chemical disinfection processes, advanced filtration and removal of nutrients such as nitrogen and phosphorus). As a consequence, the effluent discharged into the marine environment still carries a high polluting load and a strong potential for unpleasant odor release.
The problem is aggravated by the fact that many of these infrastructures are deeply undersized for the current demographic and economic reality of the region. Designed in the past for substantially smaller populations and effluent volumes, the WWTPs face unprecedented pressure today due to the continuous increase in residents, the mass tourism boom and the proliferation of new real estate developments and local accommodations. During peak attendance periods and during episodes of heavier rainfall, the retention and pre-treatment capacity of these facilities is completely exceeded, generating hydraulic overloads that undermine the very efficiency of primary treatment.
The future is shaping up under the sign of worsening and persistence of bad odors, creating an impasse that is technically and urbanistically difficult to resolve. The densification of the urban fabric around the WWTPs and the scarcity of land in the areas where they are located physically prevent the expansion of infrastructure to accommodate secondary and tertiary treatment phases, which require large-scale biological reactors, aeration tanks and secondary settling tanks. Without physical space to install these additional modules or advanced gas neutralization systems, the population will continue to be subject to increasingly intense and frequent odor emissions.
