The need to conserve water is important, as it is predicted that in approximately 20 years there will be a global water shortage. In Mexico and the rest of the world, scientists are constantly looking for methods to help conserve and improve the processes used to treat the wastewater generated and reuse it safely. In this work, Tilapia fish scales modified with acetic acid were used for the removal of heavy metals from model water. For this experiment, the following adsorbent dose range was applied: 0.4 g to 1 g; the pH ranged from 4 to 7; and the contact time varied between 60 and 120 min. A three-factor experimental design was considered, including variables such as the adsorbent dose, contact time, and pH, each at three levels. The chemical modification produced a more porous surface on the flakes, facilitating metal adsorption, as confirmed by morphological and physicochemical analyses. The results obtained confirmed the removal of 94 and 83% of Cd(II) and Pb(II) metal ions, respectively, with an bioadsorbent dose of 1 g at a pH of 4 and a contact time of 120 min for Cd(II) and an adsorbent dose of 0.4 g, a pH of 4, and a contact time of 90 min for Pb(II), with an initial concentration of 200 mg/L for both metals. The Brunauer–Emmett–Teller (BET) analysis results provide critical insights into the textural properties of modified fish scales. The modified fish scales have great potential for removing heavy metals from industrial wastewater.

During wastewater treatment (WT), sewage sludge (SS) is produced containing organic matter and pathogenic microorganisms that represent health risks so it must be stabilised. Several authors have reported secondary SS (sludge from the bioreactor for WT) stabilisation for its use in soil as fertiliser, but to date primary SS (sludge from primary settler or chemical precipitation tank in WT) is not exploited. In this study, we applied sonication and electrooxidation on primary SS in order to reduce the concentrations of total coliforms, fecal coliforms (FC), and chemical oxygen demand (COD). Here, we show that sonication, compared with electrooxidation, decreases twice as much FC in wastewater SS, and the process is influenced by the interaction of time and applied pH. Also, the interaction of pH and the current intensity influence the decrease of FC and COD in the treated primary SS by electrooxidation. Our results demonstrate that the application of sonication with pH 5 for 10 minutes decreases the concentration of FC by 31% in the primary sludge, compared to untreated sludge. It is necessary to apply complementary treatments in order to further reduce the concentrations of pathogenic microorganisms.