Effectiveness of Pennisetum purpureum and Panicum maximum planted drying beds for fecal sludge treatment at variable loading rates

BACKGROUND AND OBJECTIVES: Sustainable fecal sludge treatment poses challenges in low-resource tropical regions due to urbanization and inadequate sanitation. Planted drying beds represent a viable technology; however, their treatment performance is governed by an interplay between specific vegetation typologies and hydraulic loading dynamics. The study objectives were to assess the treatment effectiveness of two grasses, Pennisetum purpureum and Panicum maximum, at varying hydraulic loading rates of ۴۲.۹, ۶۴.۳, and ۸۵.۷ liters per day, benchmarked against unplanted beds as controls.METHODS: The experimental setup involved fifteen pilot-scale rectangular cement-brick drying beds organized into three treatment units. Each unit contained two beds with Pennisetum purpureum, two with Panicum maximum, and one control bed. Each bed measured ۱.۷۵ × ۱.۲۵ × ۱.۰ meters with a ۱ percent slope for drainage. To evaluate system performance over a four-month monitoring period, treatment efficacy was systematically quantified by monitoring the removal efficiencies of key water quality parameters, including Total Kjeldahl Nitrogen, ammonium, nitrite, nitrate, total phosphorus, phosphate, total suspended solids, biochemical oxygen demand, and chemical oxygen demand. Microbiological analyses monitored total coliforms, Escherichia coli, Shigella, and Salmonella, with assessments of eutrophication potential to evaluate the environmental impact of the effluents. FINDINGS: Planted drying beds consistently achieved higher removal efficiencies than unplanted controls across all studied parameters. Among the vegetated systems, Pennisetum purpureum achieved the highest treatment efficiencies, particularly at the lowest hydraulic loading rate (۴۲.۹ liters per day). Maximum removal efficiencies reached ۸۹.۳ percent for Total Kjeldahl Nitrogen, ۸۷.۱ percent for ammonium, ۹۰.۰ percent for total suspended solids, ۹۵.۰ percent for biochemical oxygen demand, ۹۲.۰ percent for chemical oxygen demand, ۸۹.۱ percent for total phosphorus, and ۸۹.۹ percent for phosphate. Pathogen reductions ranged from ۹۲ percent to ۹۴ percent, while eutrophication potential decreased by ۸۷.۳ percent. An inverse relationship was observed between hydraulic loading rates and treatment efficacy; furthermore, the unplanted control beds exhibited the highest vulnerability to these increased loads, demonstrating a substantial drop in operational performance.CONCLUSION: Pennisetum purpureum-vegetated Planted drying beds are a viable and cost-effective method for treating fecal sludge in tropical settings, operating at a hydraulic loading rate of ۴۲.۹ liters per day. To fully validate operational stability, scalability, and field applicability under fluctuating environmental conditions, executing extended, larger-scale investigations remains imperative.

کلیدواژه ها:

Eutrophication reduction ، Fecal sludge (FS): Hydraulic loading rate (HLR) ، Planted drying beds (PDB) ، Removal efficiency.