Research On Highway Tunnel Construction Waste Water Treatment Using Cement Coagulation Method

At present,our country's water environmental pollution is very serious and the drinking water security is also not optimistic. Along with the development of these highway congstruction ,more and more road will extend to mountain-hill areas,via water source protection areas and the river source areas. So the task that to protect the water resource along the highway is become more and more important.However, for a long time ,in highway construction projects,water environmental protection focus on the waste water treatment and emergent protection after the unexpected events in highway operating period and pay deficiently attention to the constrction waste water impact to water encironment enve lack research on it.So,to work out a way which is not only operates simply,without secondary pollution to the environment but also suitable to the characterisitics of high way construction such as have long front,and large numbers of construction camps to treatment the highway construction waste water is very important and urgent.This paper takes highway tunnel construction waste water as study object, use cement as coagulant to carry out coagulation tests and analysis the theory of cement coagulation method treatment the construction waste water. The result is of significance to treatment the construction waste water of highway ,railway and water conservancy project.Make the conclusion as follow:1.Use cement coagulation-precipitation method to treatment tunnel construction waste water not only facilities constructed simple,easy to operate,the pharmacy was convenient but also could use prejected cement effectively,make a significant reduction in the cost of processing ,besides,a result recovery and recycling of used resources can be achieved.2.Through the experimental research such as coagulant selection,the impact of dosing amount,stirring and reation time demonstrated that the disused ordinary Portland cement can be used as a kind of coagulant; for tunnel construction waste water ,when dosage is in about 2.5 g,treatment result is optimum in relative terms; mechanical agitation have almost no apparent help for enhance the removal rate; 2 hours reaction time is suitable.3. Experimental data show that the optimum removal rate of CODcr is 41.9%, but, in general it is remain at 30% - 40%; for nitrobenzene, the best removal rate is 40.5 %, but in general it is remain at about 20 % ,the removal for oil is worst among them, its removal rate is only about 12 %.4. Mechanism study indicated that the major component (C3S,C2S,C3A,C4AF) of Portland cement could make the flocculation in the water.In the cement hydration and hardening process, hydration products through adsorption-neutralisation, adsorption-bridges and net-carried off wipe off the colloidal impurities from water.