我國水污染總量管制策略評析-以桃園南崁溪為例

Abstract

環境部為維護水體環境品質，將廢（污）水排放總量管制列為後續水質管理之主要策略，而位於桃園市之南崁溪流域，因印刷電路板製造業興盛，造成廢水中排放之重金屬銅總量已超過南崁溪之涵容能力，因此桃園市政府環境保護局於106年發布南崁溪流域廢(污)水重金屬銅排放總量管制方式，期望可使流域內銅排放總量獲得控制，以保護北桃園灌溉圳路水體水質安全。 本研究透過WASP水質模式對於河川水質涵容能力之分析，探討目前總量管制政策於南崁溪執行之效果，並以數種國外常見之污染量分配方法進行分配試算，期望提出未來政策執行方向之建議。 本研究採用主流流量資料中小於日流量延時曲線中超越機率80%所對應之流量(Q80)為設計流量進行模擬，配合目前支流排水平均流量，加總各測站上游可涵容之重金屬銅總量，並計算5%的安全餘裕量(Margin Of Safety)，得到容許排放量其中大埔橋以上為1.76kg/day、龜山橋以上為3.39kg/day、大檜溪橋以上為9.20kg/day、南崁溪橋以上為16.28kg/day、崁下橋以上為26.97kg/day、竹圍大橋以上為30.71kg/day，以目前核准之排放水量及放流水標準(1.5mg/L)進行現況污染量排放估算，各河段中除龜山橋段外，其於許可發放之污染排放量均遠超過河川容許排放量。 本研究分別以等排放濃度、等排放量、現況排放濃度等去除率、分區等排放濃度、現況排放濃度等去除率分配法-分級管制、重點事業別削減、重點事業別削減-分級管制等方法進行分配，其中以重點事業別削減及重點事業別削減-分級管制等兩種方法較為可行，然總量管制中各種分配方式均難以達到完全之公平性，因此本研究建議實務上可於分配方案初步完成後，密集與流域內之權益關係人進行溝通協調，並可考慮推動污染量抵換及交易作業，使市場機制協助政策執行。

To maintain the quality of the water environment, the Ministry of Environment has designated the total quantity control of wastewater discharge as a key strategy for future water quality management. In the Nankan River Basin, located in Taoyuan City, the thriving printed circuit board manufacturing industry has led to excessive discharge of heavy metal copper in wastewater, surpassing the river’s assimilative capacity. In response, the Taoyuan City Environmental Protection Bureau issued a total quantity control policy for heavy metal copper discharge in the Nankan River Basin in 2017. This policy aims to regulate the total copper discharge within the basin and safeguard the water quality of irrigation channels in northern Taoyuan. This study utilizes the WASP water quality model to analyze the river’s assimilative capacity and assess the effectiveness of the current total quantity control policy in the Nankan River. Additionally, several commonly used international pollutant allocation methods are applied for simulation calculations to provide recommendations for future policy implementation. For the simulation, this study adopts a design flow (Q80) based on the flow corresponding to the 80% exceedance probability in the daily flow duration curve, combined with the average tributary drainage flow. The total allowable heavy metal copper load is calculated by summing the assimilative capacities of upstream monitoring stations while incorporating a 5% margin of safety. The resulting permissible discharge limits are as follows: •Upstream of Dapu Bridge: 1.76 kg/day •Upstream of Guishan Bridge: 3.39 kg/day •Upstream of Dakuixi Bridge: 9.20 kg/day •Upstream of Nankanxi Bridge: 16.28 kg/day •Upstream of Kanxia Bridge: 26.97 kg/day •Upstream of Zhuwei Bridge: 30.71 kg/day Using the approved discharge volume and the effluent standard (1.5 mg/L) for current pollution load estimation, it was found that, except for the Guishan Bridge section, the permitted pollution discharge in all other river sections significantly exceeds the river’s allowable discharge capacity. This study explores various pollutant allocation methods, including equal discharge concentration, equal discharge volume, current discharge concentration with an equal reduction rate, regional equal discharge concentration, hierarchical control based on current discharge concentration and reduction rates, targeted industry reduction, and hierarchical control for targeted industries. Among these, targeted industry reduction and hierarchical control for targeted industries appear to be the most feasible approaches. However, achieving absolute fairness in total quantity control through any allocation method remains challenging. Therefore, this study recommends that after the initial allocation plan is developed, intensive communication and coordination with stakeholders within the river basin should be conducted. Additionally, the implementation of pollutant trading and offset mechanisms can be considered to leverage market forces in supporting policy execution.