Study on Quality Requirements of Reclaimed Water for Vegetation Restoration and Technologies of Moderate Wastewater Treatment in the Coal Base of Northwest Desert Region
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【Author in Chinese】 孙凯；
【Author's Information】 北京林业大学， 环境工程硕士（专业学位）， 2020， 硕士
【Abstract in Chinese】 西北荒漠区煤炭基地干旱缺水,可用水量较少。再生水（矿井水及生活污水）是其可利用于植被恢复的主要水源之一。本研究首先研究了适用于西北荒漠区煤炭基地植被恢复的再生水水质要求,之后根据再生水水质要求对生活污水和矿井水分别利用活性污泥与生物膜复合体系及纳滤膜过滤技术进行适度处理。并研究了满足再生水水质要求的适度处理运行参数,探究了污染物的去除机理,最后根据羊场湾矿区的再生水处理和利用给出技术经济概算。对西北荒漠区煤炭基地水土植被的保育、植被多样性建立、生态平衡维护、以及自然环境改善具深刻意义。根据西北地区生活污水及矿井水原水水质,结合国家再生水相关标准以及相关再生水用于植被恢复的文献,确定了适用于西北荒漠区植被恢复的再生水水质。再生水主要污染物控制指标为:浊度≤10 NTU;悬浮物≤30 mg/L;总硬度≤450 mg/L;氯化物≤350 mg/L;TDS≤1000 mg/L;COD≤65 mg/L;NH4+-N≤20 mg/L;TP≤4 mg/L。生活污水适度处理采用序批式泥膜一体HBR（复合生物反应器）,形成污染物去除能力强的稳定活性污泥和生物膜的复合生物体系。序批式复合反应器采取厌氧-缺氧-好氧模式。达到适度污水处理要求的适宜运行工况为:进水15 min、厌氧90 min、缺氧90 min、好氧180 min、沉淀30 min、排水15 min,排泥10 d,最佳运行温度为25℃,最佳填料投加比例为1/4,最佳碳氮比为7/1。系统稳定运行5个月,结果显示序批式复合反应器具有较强的抗冲击和去污染能力,出水COD浓度为58 mg/L、NH4+-N浓度为9.4 mg/L、TN浓度为14 mg/L、TP浓度为2.8 mg/L,既保障污水中有机物的去除,又保证适量的氮磷作为植被灌溉时的营养物质。悬浮物和矿化度较高是西北煤炭基地矿井水的主要问题。结合混凝-沉淀预处理工艺去除水中悬浮物,采用以纳滤为主的膜过滤工艺达到脱盐目的。试验结果表明,混凝-沉淀预处理过程聚合氯化铝的投加量为80 mg/L,去除水中悬浮物和浊度效果最佳,出水浊度5.14 NTU、悬浮物8.55 mg/L。结合矿井水处理效果及经济性比选,选择NF90纳滤膜过滤技术。适宜的NF90膜操作压力为0.8 MPa、操作温度为25℃。采用2%的柠檬酸清洗并用氨水调节p H至2.5-4可以明显减小膜污染并且恢复膜通量。该工艺对羊场湾煤矿矿井水的处理效果明显,出水总硬度为14.64 mg/L、氯化物为331.12 mg/L、TDS为735 mg/L。在满足适度处理要求的同时,又节约了处理成本。根据工程场地—羊场湾矿区植被恢复规划,利用羊场湾矿区已建成的污水处理设施,结合本研究提出的工艺及优化运行条件,给出了符合羊场湾矿区植被恢复的再生水适度处理技术的工程概算。生活污水处理工艺改进后效率提升30%,处理成本约为0.98元/吨,年平均生活污水总处理成本为40.75万元;矿井水处理成本为0.182元/吨,年平均矿井水总处理成本为114.478万元。
【Abstract】 The coal base in the northwest desert region is dry and short of water.Reclaimed water（mine water and domestic sewage）is one of the main water sources available for vegetation restoration.In this study,the water quality requirements of reclaimed water for vegetation restoration in the coal base in the northwest desert region were firstly studied.According to the water quality requirements of reclaimed water,the composite system of activated sludge and biofilm and the nanofiltration membrane filtration technology were used to treat domestic sewage and mine drainage.In addition,the operation parameters of moderate treatment to meet the quality requirements of reclaimed water were studied,and the removal mechanism of pollutants was explored.Finally,the technical and economic estimates were given according to the treatment and utilization of reclaimed water in yangchangwan mining area.It is of profound significance to the conservation of soil and water vegetation,the establishment of vegetation diversity,the maintenance of ecological balance and the improvement of natural environment in the coal base in the northwest desert region.According to the quality of domestic sewage and mine water in northwest China,combined with the relevant national standards of reclaimed water and relevant literature on the use of reclaimed water in vegetation restoration,the quality of reclaimed water suitable for vegetation restoration in northwest desert areas was determined.The main pollutant control index of reclaimed water was:turbidity≤10NTU,SS≤30 mg/L,Total hardness≤450 mg/L,Chloride≤350 mg/L,TDS≤1000 mg/L,COD≤65mg/L,NH4+-N≤20 mg/L,TP≤4 mg/L.In the moderate treatment of domestic sewage,sequence batch sludge membrane integrated hybrid bioreactor（HBR）was used to form a composite biological system of stable activated sludge and biofilm with strong pollutant removal capacity.Sequence batch composite reactor adopts the anaerobic-anoxic-aerobic mode.Suitable operating conditions to meet the requirements of moderate sewage treatment were:15 min of water inlet,90 min of anaerobic,90 min of anoxic,180 min of aerobic,30 min of sedimentation,15 min of drainage,10 days of sludge drainage,the best operating temperature was 25℃,the best packing proportion was 1/4,the best carbon/nitrogen ratio was 7/1.HBR system stably operated for 5 months,and according to the results HBR had stronger ability to resist shock and decontamination,with an effluent COD concentration of 58 mg/L,NH4+-N concentration of 9.4 mg/L of 14 mg/L,TN concentration of 14 mg/L,TP concentration of 2.8 mg/L,ensuring both the removal of organic matters in sewage and the right amount of nitrogen and phosphorus as nutrients for vegetation irrigation.Suspended matter and high salinity are the main problems of mine drainage in northwest coal base.The membrane filtration process based on nanofiltration was used to remove suspended solids in the water.The experimental results showed that the dosage of polyaluminum chloride in the coagulation-precipitation pretreatment process was 80 mg/L,and the removal of suspended solids and turbidity in the water was the best,with an effluent turbidity of 5.14 NTU and a suspended solid of 8.55mg/L.NF90 nanofiltration membrane filtration technology was selected in combination with mine drainage treatment effect and economic ratio.The appropriate operating pressure of NF90 film was 0.8MPa and the operating temperature is 25℃.Cleaning with 2%citric acid and adjusting p H to 2.5-4with ammonia can significantly reduced membrane fouling and restored membrane flux.The treatment effect of this process on mine drainage in Yangchangwan Coal Mine is obvious,and the effluent total hardness was 14.64 mg/L,the chloride was 331.12 mg/L,and the TDS was 735 mg/L.At the same time,the treatment cost was saved.According to the vegetation restoration plan of the engineering site-yangchangwan mining area,the project estimation of the moderate treatment technology of reclaimed water in accordance with the vegetation restoration technology of yangchangwan mining area was given by using the sewage treatment facilities already built in yangchangwan mining area,combining with the process and optimized operation conditions proposed in this study.After the improvement of domestic sewage treatment technology,the efficiency was improved by 30%,the treatment cost was about 0.98 yuan/m3,and the annual average total domestic sewage treatment cost was 407,500 yuan.The cost of mine water treatment was 0.182 yuan/m3,and the annual average total cost of mine water treatment was 1.14478million yuan.