| 摘要: | 國內澎湖地區因地表水源缺乏，故目前海淡廠或鹹井水淡化廠為當地民生用水之主要供給來源，其中淡化程序之水處理方式以RO逆滲透為主。本研究於澎湖烏崁海淡廠設立薄膜試驗模組，以MF、UF薄膜當前處理之薄膜清洗進行深入探討，包括薄膜的選用、清洗時機、藥劑選擇以及清洗時間，找出最佳清洗程序。並於每一試程結束後，進行積垢物之萃取分析，以全面瞭解造成膜阻塞之成因。
以HPI PTFE膜作為海水淡化前處理單一藥劑清洗建議選擇NaOCl作為清洗藥劑，而當無法避免逐漸嚴重之通量衰減時，輔以HCl清洗。而當使用HPO PTFE膜，建議清洗藥劑以單獨HCl清洗為主，增加NaOCl清洗助益不大。此外，某特定範圍孔徑(因原水水質而異)可能導致顆粒塞進膜孔，而造成通量不易恢復。本試驗中造成HPO PTFE膜通量恢復率不佳之原因即可能為大小約0.2~0.8 µm之海洋菌細胞阻塞進膜孔纖維內而無法洗出所致。
以UF作為海淡前處理，以NaOCl清洗之通量衰減較輕微，且可獲得較佳之通量恢復率。藉由膜表面洗後殘留物分析結果，HCl酸洗殘留無機元素較少；鹼性洗劑NaOH與NaOCl清洗較易使膜表面殘留無機元素；然針對有機性汙染物則PVDF以NaOCl清洗效果較佳。建議UF膜以NaOCl清洗較佳。
本試驗評估之清洗程序包含單一藥劑清洗(HCl、NaOH、NaOCl)及雙重藥劑(HCl-NaOH、NaOH-HCl及NaOCl-HCl)清洗。結果顯示，以親水性PTFE膜作為海水淡化RO前處理時，單一藥劑清洗建議選擇NaOCl作為清洗藥劑，而此仍無法避免逐漸衰減之通量；最佳之清洗方式為NaOCl-HCl清洗。而PVDF膜之試驗可發現無論何種組合，平均通量大致都隨清洗次數降低。而以單一清洗藥劑而言，HCl及NaOCl之平均通量表現皆不錯，而整體而言，清洗效果以雙重清洗藥劑之NaOCl-HCl組合為最佳。
Due to the lack of surface water resources, desalination of seawater has been carried out in order to supply fresh water in the Penghu island region. In general, the Penghu Seawater Desalination plant uses reverse osmosis (RO) equipped with membrane cleaning. The effect of membrane material, duration of cleaning time and type of chemical reagents on the membrane cleaning efficiency has been investigated. The study also determined the effect in the application of MF and UF on the efficiency of membrane operation. At each run, samples of the membrane scale was obtained and analyzed in order to effectively understand the contributing factors that cause membrane fouling.
In the desalination process, NaOCl is the recommended chemical agent to be used in cleaning HPI PTFE membranes. During a severe flux reduction, HCl is utilized as a supplementary chemical agent in membrane cleaning. However, HCl as chemical agent is not recommended in cleaning HPO PTFE membranes. It is observed that increasing dosage of NaOCl does not have a significant effect in improving the membrane cleaning efficiency. In this study, the flux recovery rate for HPO PTFE membranes was poor due to irreversible pore blocking caused by marine bacterial cells with size range of 0.2~0.8 µm.
In utilizing UF as a pretreatment procedure, better flux recovery rates were attained where lower dosages of NaOCl was used and smaller flux reduction was observed. During membrane cleaning using HCl, the membrane scales obtained were composed of inorganic elements of acidic nature. The residual inorganic elements are effectively washed from the membrane surface using NaOH combined with NaOCl while organic pollutants are effectively removed from the membrane surface using NaOCl alone. It is observed that NaOCl is more suitable and more effective in cleaning UF membranes.
removal of nitrate from raw water.
Raw water was obtained from a groundwater monitoring well from central region of waterworks in Taiwan. In the ED study, nitrate removal efficiency was examined, the water quality of the product effluent was analyzed and power cost analysis was determined. The results show that increasing the voltage applied causes an increase in the nitrate removal efficiency. Within the voltage range of 30 to 60V, about 52.50% to 63.34% of nitrate removal efficiency was obtained in shorter reaction time of 30s. Under an applied voltage of 60V, the removal rate was observed to decrease from 63.34%
to 44.17% as flow rate was increased from 2 L/min to 5 L/min.
The effect of alkalinity on nitrate removal is insignificant. Using a low voltage, groundwater was treated using ED for two treatment cycles. An increase in power consumption but with no apparent increase in the recovery of product water (64%) was observed. Electricity consumption was observed to be stable, where a voltage increase of 10 V corresponds to a 0.1 kWh consumption of electricity. The electricity utilized in one treatment cycle of EDR is an average of 3 kWh. A removal efficiency of 30.89% to 66.90% would utilize a voltage in the range of 10 to 60 V, when the nitrate concentration about
11.7mg/L to 17.1mg/L.
Using a voltage of 35 V, one ton of power is consumed of 3.05 degree that provides a 55% residual nitrate and 45% nitrate removal. Hydroponic cultivation method was utilized in the treatment of nitrate from wastewater, where nitrate was absorbed using hydroponic vegetables. The uptake of nitrate could also
serve as a fertilizer in the growth of hydroponic vegetables. |
