A source-to-sea decision-support framework for wet-weather wastewater load management: evidence from Jiaozhou Bay

Abstract

Coastal concentration compliance can overlook increased wastewater throughput during wet weather. We developed a source-to-sea decision-support framework using 2019–2022 wastewater, river, and marine observations from Jiaozhou Bay, China. The analysis combined source-record auditing, hydraulic and concentration decomposition, benchmark comparison, and source–receptor chronology. At Loushan wastewater treatment plant, throughput increased by 87.5% from the second to the third quarter of 2020 while total phosphorus remained low at 0.06–0.07 mg L −1 . The corresponding operational loading estimate increased by 118.8%. Hydraulic amplification persisted across seven benchmarks, whereas the direction of estimated load change depended on the reference concentration. Earlier biological surveys characterized receiving-water conditions and informed subsequent monitoring design. The resulting five-stage framework connects data validation, hydraulic review, synchronized source-to-sea monitoring, sediment and benthic follow-up, and adaptive evaluation. It uses hydraulic amplification to prioritize representative effluent sampling and assigns each stage to existing source, river, or marine monitoring functions. Explicit benchmark rules and a proposed sampling timetable make the workflow reproducible and operationally interpretable. The framework provides a practical route from sparse concentration records to coordinated coastal load management, with operational estimates used for screening and representative measurements required for regulatory load assessment.