Integrated assessment of decentralized wastewater treatment plants in a semi-arid region in Bolivia

Abstract

This study comprehensively evaluates four wastewater treatment plants intended for agricultural reuse in a semi-arid low-moderate temperature region. It considers environmental, technical, economic, and social perspectives. Anaerobic baffled reactors with hybrid gravel filters (ABR + HGF + VGF) proved the most efficient, with moderate requirements in space, O&M, and energy, albeit the highest treatment cost. Up-flow sludge blanket reactor with activated sludge (UASB + AS) demonstrated high efficiency and compactness, with moderate treatment costs. However, it incurred high energy demands, complex O&M, and more sludge generation. UASB with horizontal gravel filter (UASB + HGF) was among the most land-intensive systems, with moderate costs and O&M requirements, and low energy consumption. However, it fell short of meeting certain environmental criteria. ABR with stabilization ponds (ABR + PONDS) emerged as the most economical, with low energy consumption, but was also among the most land-intensive and failed to achieve adequate effluent quality. Socially, all WWTPs were well accepted for agricultural reuse benefits. In terms of odor perception, UASB + AS and ABR + HGF + VGF exhibit the lowest impact. The Most Appropriate Treatment Technology Index ranked ABR + HGF + VGF and UASB + AS as adequate technologies, while UASB + HGF and ABR + PONDS were poorly adequate. The study recommends a four-dimensional assessment for selecting the most suitable technology, considering the specific context.