Research On The Process Of Using Reclaimed Water For The Water System Of Hefei City

Artificial scenic water with small size, poor liquidity, low environmental capacity, and low self-purification ability, which would be easily polluted by climate change, human activities and the surrounding environment. The sources of current l scenic water comes from tap water or external lakes (rivers), but, tap water is generally not used as a supplementary water source due to high cost and waste of water, while in recent years external lakes (rivers) were polluted seriously by which as a supplementary water quality can not meet the scenic requirements, so some cities start to implement Wastewater Treatment Plant secondary sedimentation tank's drainage treat for reusing back in scenic water. When reclaimed water is used for artificial water or adding to natural water, we need to strictly control its own water quality especially reducing its eutrophication element-phosphorus, which plays a very important role in controlling the algae's growth and protecting the viability and safety of the reclaimed water.In order to study the Coagulation Technology for Reclaimed Water Phosphorus Removal , we use the South Wastewater Treatment Plant secondary sedimentation tank's drainage for raw water for the beaker test, transit small-scale coagulation tests (the best conditions of coagulation tests, Coagulant selection tests, the best Coagulant dosage tests).Also in order to study the factors affecting the growth of algae and preventive measures, we done some research by the Static Experiments (the proportion of nitrogen and phosphorus impacting algal growth and water environment factors.) At the same time we transit mechanism analysis and medium test, to make the research combine with the protection, to supervise engineering function.1,the best conditions of coagulation testadd Coagulant to the secondary sedimentation tank's drainage, admixture time must be 60 seconds, admixture intensity must be lack of 500 s-1, whisk intensity must between 10 s-1and 100 s-1, is different if you use different Coagulants. But its reaction time must be controlled in 10 minutes.2,Coagulant selection testWe select five Coagulants(PAC,Al2(SO4)3,FeCl3,FeSO4,PAFC).Their remove effects are as follows: (1)dephosphorization effect: FeCl3>Al2(SO4)3>PAC>PAFC>FeSO4;(2)dissolved dephosphorization effect:Al2(SO4)3>FeSO4>FeCl3>PAC>PAFC;(3) nephelometer removal: FeCl3>PAC>PAFC>Al2(SO4)3>FeSO4;(4)organic matter remove is light , FeCl3>PAFC>Al2(SO4)3>FeSO4>PAC.3,experiment of the best dosage trialWhen the raw water turbidity change from 1.9 NTU to 15.5NTU, TP from 0.3 mg/L to 0.7mg/L ,the dosage between 3 mg/L and 5mg/L,can ensure the drainage water quality : TP <0.5mg/L, turbidity <3NTU.When removing phosphorus with coagulant A in combination with combination B, A30%B70% ratio is better than other ratios to remove phosphorus and turbidity. In the condition of A30%B70%, 6mg/L, 8mg/L, 10mg/L can be the best dosage which correspond to the TP concentration in the range of: <0.8mg/L, 0.8mg/L~1.25mg/L,> 1.3mg/L.When the total dosage of coagulant A and coagulant C is 10 mg/L, the optimal ratio is A9.7mg/L,C0.3mg/L. In this ratio, the treatment of raw with low and high levels of TP is very good, the removal rate can reach 90%. When the turbidity of raw is less than 5NTU, the turbidity of the effluent is below 0.5NTU. The removal rate is higher with the increase of turbidity.4,Take sewage plant secondary sedimentation tank's drainage for raw water to do the Pilot testThe dosage of PAC in Pilot test is 10 mg/L. The results show that when the dosage of TP in raw water is 0.5~1.0mg/L,the dosage of TP of effluent is below 0.3mg/L; the rate of turbidity removal is 50%; when the dosage of COD in raw water is above 50mg/L, the rate of removal is between 50%~70%, and the most removal comes from the organic flocculation attached to macromolecular; In the effluent, the average dosage of SS is 3.5mg/L;the average dosage of TP is 0.19mg/L;the average dosage of TN is 0.19mg/L; the average dosage of COD is 30 mg/L; pH is between 6.5~8.5.5,the Static Experiments with different proportion of nitrogen and phosphorus in the raw water.Studies shows that, for the growth of algae, m(N)/m(P) is 3～8 which has a promoting effect; when m(N)/m(P) is more than 10, the inhibitory effect appeared; In addition to m(N)/m(P), but also affected by other factors. It is possible that, under certain conditions, the impact of m(N)/m(P) on the algal growth would be more significant. In the early growth of algae when it will outbreaks, DO and pH levels will rise and get to a maximum.