Using the Simulation Model to Verify Water Quality Improvement of Er-Jen River through Pig Toilets Promotion

[[abstract]]本研究運用污染源頭改善為思維–於豬舍內設置豬廁所設施，針對台灣地區深受畜牧業污染之河川-二仁溪流域，探討豬廁所之設置前後對於二仁溪污染負荷量之削減效益，除以河川之最大涵容能力為基礎探討河川之可承受污染負荷量外，並經由水質模式之建置與率定作為豬廁所之設置成效之佐證。 蒐集台灣地區宜蘭、彰化、雲林、台南及高雄等豬舍示範戶於豬廁所設施設置，對其清洗水量、清洗頻率、污染削減量等效益予以評估分析。於傳統平面沖水式豬舍中設置『豬廁所』設施，顯示可減少豬舍清洗13 4~52 6%用水量，同時在減少豬舍清洗時間與頻率及增加篩除豬糞上皆有顯著之污染削減效益。在搭配豬糞尿廢水即時進行固液分離程序，可提升污染物削減效益，放流水污染削減量平均約40%。 在總量管制架構下，本研究利用線性規劃程式-LINDO，評估二仁溪於中游河段設置豬廁所後，在符合台灣地區水質指標RPI嚴重污染以下等級，即符合BOD濃度≦15mg/L條件下所能承受之最大污染物含量。結果顯示於枯水季水量不足下，部分河段污染負荷已超出其河川涵容能力，另分析補助入鄰近旗山溪水源下對二仁溪涵容能力提升助益，結果顯示當灌溉期間補助旗山溪較潔淨水質約1 cms後，二仁溪之BOD涵容能力可提升至10 544 8 kg/d，已接近該流域每日污染排放量，水質獲得明顯改善。 承上，本研究同時利用水質模式QUAL2K，進一步分析二仁溪BOD涵容能力下現況及模擬其推動豬廁所後之效益。設定中游河段佈設3 900座豬廁所，在各集污區與二仁溪匯流點下游最近之『高速公路橋』站為檢核點，針對二仁溪中游模擬結果， BOD、NH3-N、SS改善率分別為19 87%、14 62%、10 26%，DO則由0 8mg/L提昇至1 4mg/L，顯示出可降低畜牧廢水排入二仁溪對水體造成之影響。再模擬增加上游旗山溪越域引水1cms對河川水質改善，結果BOD、NH3-N改善率大幅增加，分為73 68%及77 22%，DO由0 8mg/L提升為5 42mg/L，SS濃度雖因旗山越域引水質中無機粉砂偏高提高改善率降低為-12 72%，但整體河川水質RPI指標由嚴重污染之8 3降級為中度污染之5 5。 故建議未來除繼續推動豬廁所政策以控制畜牧污染排放量外，在枯水季時由旗山溪適時補助潔淨水源及搭配推動其他減污作為，為同步需採取之措施。[[abstract]]Applying the concept that pollution should be overcome at the source through pig toilets were installed in pig pens to reduce livestock pollution in Taiwan’s Er-Jen River basin which is substantially affect by this type of pollution The study investigated the effects of pig toilet installation for reducing pollution load in the Er-Jen River In addition to exploring the pollution load the river could sustain based on the maximum assimilative capacity a water quality model was established and calibrated to verify the effects of pig toilet installation This research focused on evaluating the effectiveness of pig toilets in reducing pollutants from farms in Ilan Changhua Yunlin Tainan and Kaohsiung areas by assessing water usage cleaning frequency and pollution loads Pigs were trained to use pig toilets so the area that needed to be washed and the wastewater produced could be minimized Training conducted at farms in Ilan Changhua Yunlin Tainan and Kaohsiung indicated that pigs could be effectively trained to use the pig toilet As a result water usage reduced by 13 4-52 6% The amount of time and frequency required to clean the pens also reduced dramatically Pig toilets coupled with immediate solid-liquid separation of wastewater and reduced the initial pollution load The results showed that indeed can enhance the overall effectiveness of pollutant reduction pollution reductions averaging about 40% Using a total maximum daily load framework the Linear Interactive and Discrete Optimizer a linear programming system was employed to evaluate the maximum pollutant content that the Er-Jen River could sustain to ensure that the river remained below the heavily polluted level defined in the Taiwanese river pollution index (RPI) [(i e the BOD concentration ≦15 mg/L)] The results showed that during dry seasons the pollution load in particular reaches of the river exceeded the river assimilative capacity because of low water levels Subsequently an analysis was conducted to evaluate whether introducing water from the neighboring Chi-Shan River would be beneficial for increasing the assimilative capacity of the Er-Jen River The results showed that introducing 1 cms of cleaner water from the Chi-Shan River during irrigation periods increased the Er-Jen River BOD assimilative capacity to 10 544 8 kg/day This approached the daily pollution emission level in the basin and indicated significant improvement Moreover the water quality model QUAL2K was used to analyze current Er-Jen River status and simulate the water quality difference after confirming BOD assimilative capacity following pig toilet installation In the simulation for the middle reaches of the Er-Jen River 2 500 pig toilests were assumed to set and the “highway bridge” nearest the lower reaches of the Er-Jen River confluence and the pollution zones was used as a check point The results showed that continued promotion of the pig toilet policy reduced the levels of BOD NH3-N and SS by 19 87% 14 62% and 10 26% respectively and DO increased from 0 8 to 1 4 mg/L indicating that the method reduced the impact of livestock wastewater discharging into the Er-Jen River However the base flow volume of the Er-Jen River is low and the assimilative capacity of particular reaches is insufficient for low flow volumes (Q75) Therefore the pig toilet policy cannot sufficiently improve water quality to reduce the RPI and remove the river from its currently heavily polluted status to a polluted status (or lower) Nevertheless to examine potential improvement cross-watershed diversion was added in the simulation After introducing 1 cms of upstream Chi-Shan River water BOD and NH3-N contaminants were reduced significantly by 73 68% and 77 22% respectively and DO increased from 0 8 to 5 42 mg/L Although the SS concentration decreased to -12 72% because the Chi-Shan River cross-watershed diversion contains high levels of inorganic silt overall river-water RPI decreased from 8 3 (heavily polluted) to 5 5 (polluted) In addition to promoting the pig toilet policy which is beneficial for controlling livestock pollution emissions supplying clean water sources from Chi-shan River and promoting other measures is also necessar