The Study Of Cement + PAC Processing Tunnel Construction Wastewater Technology

Tunnel can improve the linear, solving the elevation barriers, shorten the mileage, reduce damage to vegetation, and has many other advantages. But in tunnel construction period, usually only value the construction technology, technical scheme, construction schedule and other issues, the environmental problems for tunnel construction are given inadequate attentions. So the influence on the quality of downstream river water is usually larger, therefore the research of the tunnel construction wastewater treatment is very important and significant.This thesis a subtopic of the shaanxi province communications department project "the study of the wastewater treatment in mountainous area highway tunnel construction," based on the earlier research, further studies are carried out to learn the effect of processing tunnel construction wastewater by using different coagulant and the cement + PAC, through laboratory testing data sorting and analysis the mechanism of coagulants, cement and cement + PAC, reached the following conclusions:1. By using the traditional aluminium salt and physico-chemical, polyaluminium salt, polyblend physico-chemical, organic polymer flocculant and cement processing tunnel construction, found that cement and traditional wastewater coagulants had no obvious difference in the effect compared.2. Existing cement as a coagulant research showed the cement may contain something that could contribute to flocculation effect, using cement and coagulants cooperate processing tunnel construction, find that in several combination,the effect of cement + PAC is the most obvious.3. using cement + PAC as flocculating agent, agitation, reaction time and pH experiment shows that the best reaction condition of cement and PAC is 20min for precipitation,500r/min, with neutral partial alkaline pH.4. Through the reduce experiment of cement + PAC concluded that when the cast of cement + PAC is 1g + 0.027 g the effect of the pollution removal get best, the removal rate of CODcr is 88.04%, nitrobenzene 24.79%, petroleum 14.54%.by adding cement, could reduce the dosage of PAC, reduce the cost.5. Mechanism research shows that cement + PAC effect is better than cement or PAC alone. One possible reason is that the micro constituent in the cement became the PAC's coagulant, promoted the coagulation process.