---

Background & objectives: Pharmaceutical wastewater contains high concentrations of organic matter, high salt and difficult biodegradability, so it must be treated before discharge to the environment. In this study, it is aimed to evaluate the treatment of pharmaceutical wastewater (methadone feedstock and neutralized capecitabine) using chemical and biological methods.
Methods: The laboratory evaluation of this study was performed in two parts: The first part included the study of wastewater treatment of methadone production using chemical coagulation and flocculation method with FeCl₃, PAC and Alum as coagulants (at concentrations of 100 mg/L, 500 mg/L, and 1000 mg/L), and cationic flocculant (at concentration of 1 mg/L), and at two pH values of 7.5 and 14 in the Jars test apparatus. The second part included of the treatment capability of wastewater produced during neutralization section of capecitabine drug according to the following steps: a) the chemical pretreatment using PAC and Alum coagulants (at concentration of 4000 mg/L) and anionic, cationic and neutral flocculants (at concentration of 20 mg/L), followed by the anaerobic biological treatment for 67 hr, and b) the anaerobic biological treatment for 41 hr followed by the chemical treatment using PAC and Alum coagulants and anionic and cationic flocculants. In this study changes in chemical oxygen demand (COD), pH, turbidity and total dissolved solids (TDS) of wastewater were investigated.
Results: At pH=7.5, the best treatment efficiency of methadone feedstock production wastewater was observed at 100 mg FeCl₃/L (COD removal of 35.8±0.8%, turbidity removal of 99.4±0.1%, and TDS removal of 7%) and at pH=14, the best performance was obtained using 1000 mg FeCl₃/L (COD removal of 42.5±0.0%, turbidity removal of 97.6±0.1%, and TDS removal of 51.6%). The highest combined chemical and biological treatment efficiencies were obtained for wastewater including neutralized capecitabine by Alum coagulant and cationic flocculant (COD removal of 61.3%). While, the highest combined biological and chemical treatment efficiency for this wastewater was obtained by Alum coagulant and anionic flocculant (COD removal of 39.0%).
Conclusion: Due to the characteristics of the pharmaceutical industry wastewater, the use of chemical methods, in addition to having good removal efficiency as the main stages of treatment, can also be used as pre-treatment for biological processes.

---

Background & objectives: The attached growth process is an aerobic method for wastewater treatment where microorganisms grow on the surface of a substrate. In this study, a small-scale attached growth reactor was used for wastewater treatment for eight weeks in rural and small communities. 
Methods: The average operational parameters of HRT, DO, MLSS, and MLVSS were measured in the pilot-scale reactor. The reactor's ability to remove suspended solids, organic materials such as BOD5, COD, and nutrients like TP, TKN, 4NH-N, as well as coliforms, was also analyzed. Coliform tests were conducted using the MPN method and dilution, BOD5 tests were performed with a BOD measuring device, and COD tests were carried out using the COD Set-Ups COD VARIO method and purchased kits. 
Results: The average removal efficiency for BOD5, COD, TP, TKN, NH4-N, TSS, fecal coliforms, and total coliforms was 73.1%, 82.5%, 48.9%, 58%, 82%, 92.8%, 85%, and 81%, respectively.
Conclusion: The results of this study indicated that the stability of the microbial biomass present in the biofilm is observed after several weeks of system operation, and the attached growth system effectively reduces solids and organic compounds during its various stages. Additionally, acceptable results regarding total and fecal coliforms were obtained in the absence of any disinfection, indicating that the attached growth system can be a suitable option for wastewater treatment in small communities.