Study On Nitrogen And Phosphorus Removal In Domestic Wastewater By Immobilized Chlorella Pyrenoidosa

The water pollution caused by nitrogen and phosphorus has become seriously day by day,and waters eutrophication is becoming more and more badly.So waters ecosystem and peoples' health has been damaged severely.The removal of nitrogen and phosphorus has become nonneglectable.Immobilized chlorella pyrenoidosa can remove nitrogen and phosphorus from secondary effluent effectively.The separation problem between algae and water in nitrogen and phosphorus disposal by suspended algae can be solved too.At the same time we can gain some chlorella pyrenoidosa of a certain value. This study contains a lot of examination data and studies the influences of factors to the removal of nitrogen and phosphorus by immobilized chlorella pyrenoidosa.For example,nitrogen and phosphorus contents and nitrogen/phosphorus ratio,the number of algae grains,starvation disposal(starvation time and nitrogen and phosphorus starvation),pH value,oscillating,aeration(aerating or not and aeration intensity). Under the premise of these factors' best conditions I studied factual wastewater,tested its removal effects on secondary effluent.This study provides some basic studies for the project application of nitrogen and phosphorus removal from wastewater by immobilized chlorella pyrenoidosa.(1)The study results of nitrogen and phosphorus contents and nitrogen/ phosphorus ratio on the removal of nitrogen and phosphorus by immobilized chlorella pyrenoidosa show that when nitrogen/phosphorus ratio is between 3:1 and 10:1,the removal rate of NH₄⁺-N decreases as the ratio increases;the higher the initial content of phosphorus the little the final PO₄^3--P removal rate is,but the higher PO₄^3--P removal quantity is.When nitrogen/phosphorus ratio is 5:1,PO₄^3--P removal rate is best and can reach 100%;the higher the initial content of phosphorus the high PO₄^3--P removal rate is;so well as its removal ammount and speed.(2)The study results of the number of algae grains on the removal of nitrogen and phosphorus by immobilized chlorella pyrenoidosa show that under the reasonable nitrogen and phosphorus contents and nitrogen/phosphorus ratio,the removal content and rate of NH₄⁺-N are all higher at the density of 1000 per 150 mL wastewater,and the removal effect of NH₄⁺-N is preferably,the removal rate can reach 97.22%.But the removal content and rate of PO₄^3--P are all higher at the density of 1500 per 150 mL wastewater,and the removal effect of PO₄^3--P is preferably,the removal rate can reach 66.41%.For the removal rate of NH₄⁺-N,the order is 1000＞800＞1500＞300 grains per 150mL manual wastewater,and for PO₄^3--P,the order is 1500＞1000＞800＞300 grains per 150mL manual wastewater.If the gains are too many the chlorella pyrenoidosa' nutrition absorbtion of nitrogen and phosphorus will be controlled.(3)The study results of the starvation time on the removal of nitrogen and phosphorus by immobilized chlorella pyrenoidosa indicate that the removal amount of NH₄⁺-N is larger at the condition of non-starvation(contains disposal time 24 hours), after 24 hours of starvation,the removal rate of nitrogen and phosphorus can be promoted at the beginning,when the starvation time is 48 hours the removal amount of PO₄^3--P is higher.Nitrogen and phosphorus removal effect is the best at the condition of non-starvation(contains disposal time 24 hours).The study results of the nitrogen and phosphorus starvation time on the removal of nitrogen and phosphorus by immobilized chlorella pyrenoidosa indicate that N starvation can promote the removal amount and rate of PO₄^3--P.P starvation can promote the removal amount and rate of NH₄⁺-N.(4)The study results of pH value on the removal of nitrogen and phosphorus by immobilized chlorella pyrenoidosa indicate that the best condition of nitrogen and phosphorus removal is neutral but a little alkalescence from 7.02 to 7.19.(5)The study results of oscillating on the removal of nitrogen and phosphorus by immobilized chlorella pyrenoidosa indicate that oscillating can promote the removal rate and amount,but the chance between grains becomes more and more because of oscillating,so the grains are easy to disorganize and break off,a part of chlorella pyrenoidosa and alginate gelatin suspend in wastewater,and the turbidity becomes larger,so the water will be contaminated again.If we want to promote the removal effect of nitrogen and phosphorus we should cut the time of oscillating,for fear that the water could be polluted again.(6)The study results of aeration on the removal of nitrogen and phosphorus by immobilized chlorella pyrenoidosa indicate that aerating in the night can promote the removal rate of nitrogen and phosphorus prominently,but the total removal amount can't be promoted prominently.The study results of aeration intensity on the removal of nitrogen and phosphorus by immobilized chlorella pyrenoidosa indicate that the better condition on the removal of NH₄⁺-N is 2L/min-3L/min;and the better condition on the removal of PO₄^3--P is 0.2L/min-1.5L/min.(7)This study takes the secondary wastewater from Mai Island and Tuan Island as a test,and in the promise of the best condition it shows that during 4 days the removal rate of nitrogen and phosphorus can reach nearly 80%and 100%.Nitrogen and phosphorus removal is also be influenced by wastewater quality.If there are some poisonous matter to alginate gelatin immobilized chlorella pyrenoidosa the method will not be adopted.