| Currently, due to surface water pollution and stringent drinking water quality standards, conventional water treatment processes need to be continuously optimized to remove certain pollutants and to deal with fluctuating raw water characteristics. It is crucial to develop innovative techniques for surface water treatment and seawater pretreatment for their application in drinking water production.Under such circumstances, an integrated membrane coagulation reactor (MCR) process combining coagulation, microfiltration and/or powdered activated carbon (PAC) adsorption was investigated for Bohai seawater pretreatment prior to the RO desalination membrane, to evaluate its feasibility to be used as the seawater reverse osmosis (SWRO) pretreatment. Long-term performance results showed that the parameters of the pretreated seawater (silt density index/or SDI, turbidity, total iron concentration and pH value) were absolutely superior to RO feed water requirements and even more consistent, excluding the chemical oxygen demand (CODMn), which varied with the raw seawater quality. The orthogonal experiment has shown that some factors has affected the membrane fouling and decreased the pretreatment capacity in decreasing order as: PAC dosage, duration of air scouring, ratio of air to permeate, and frequency of air scouring. As a result for this lab-scale test, the pretreatment capacity was optimized under the following conditions: no PAC dosage, 20 minutes of air scouring duration, ratio of air to permeate is 10, and air scouring every 8 hours. Membrane cleaning experiments have shown that the fouled membrane specific flux could be ultimately restored after chemical cleaning. However, the main reason for membrane specific flux decline lies in the formation of the cake layer on the membrane surface, and dissolved organic matters is considered as the main foulants. Compounds of magnesium, aluminum, silica, calcium and iron are the inorganic foulants on the membrane surface, which cause little decline of membrane specific flux, while fouling due to microorganism is almost unapparent.On the other hand, continuous lab-scale membrane bioreactor (MBR) tests have proven that, MBR treating micro-polluted lake water could attain a good quality of treated water in terms of the removal of organic pollutants and ammonia nitrogen. MBR process for micro-polluted surface water treatment could not only remove the organic pollutants, but could simultaneously remove TCP with the mechanisms of secondary substrate utilization and NOM inducing effect. For the raw water TCP concentration ranged between 40μg/L and 385μg/L, the average removal efficiency was 96.13%, and the average TCP concentration of treated water lower than 4μg/L and met the requirement of Drinking Water Quality Standard of China (CJ/T206-2005) issued by the Ministry of Construction. In addition, a series of intermittent batch tests showed that biological degradation plays a major role in the removal of phenolic compounds by MBR and the TCP biodegradation follows zero-order kinetics with a rate constant of 1.65μg/(L.min). The maximum specific utilization rate qmax and the affinity constant Ks of TCP were determined by fed-batch reactor tests and the values were 0.060d-1 and 0.235 mg/L respectively. The result showed that, microoganisms with good affinity for TCP could be cultivated in the MBR process, which was favorable for the biodegradation of trace TCP.This research confirmed that the MBR system and the MCR integrated coagulation-microfiltration process both have the potential to efficiently substitute the conventional surface water treatment and SWRO pretreatment processes respectively.
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