Research To Influencial Factors Of Analytical Methods Used To Determine Cyanide For Final Effluent In Wastewater Treatment Plant

Cyanide is highly toxic at low concentrations and it’s toxic to animals and human,therefore, the determination of the cyanide concentration is particularly critical. AmericanWildcat Hill sewage treatment plant effluent discharge measurement results of cyanidewastewater treatment plants often exceed emission limits (8μg/L), this paper choose cyanideselective electrode and spectrophotometer for measuring the sewage treatment plant in orderto find the determination of the cyanide concentration exceeds the reason emission limits.Selective electrode method and Microtubule Spectrophotometer method used todetermine cyanide are of high accuracy, selective electrode method detection limit (MDL) is0.01mg/L, it can only be used in this research on influencial factors of cyanide determinationmethod, and microtubule spectrophotometer method MDL was5μg/L, it is more suitable forcyanide determination for wastewater treatment plant final effluent.Cyanide concentration measured by selective electrode method increased and thendecreased with the sample holding time increasing, so cyanide determination should be doneimmediately after sampling, generally,cyanide measurement should be done in15min.Bycomparing wastewater samples before and after chlorination from Wildcat Hill wastewatertreatment plant, chlorination and dechlorination is not the reason why cyanide concentrationincreased. The volume of reagent bottles for cyanide samples made influence on cyanidedetermination, the results showed that the samples stored in the small reagent bottles,resultswere higher than bigger ones, it may due to more HCN volatilization in bigger reagentbottles.After experimental correction, microtubule spectrophotometer method selected578nmas maximum absorption wavelength.Under the same sample holding time, samples saved withno headspace benifited improving the the method accuracy.Fllowing the sequence of adding sulfamic acid and then cyanide samples，then adding NaOH to improve pH,the samples can beremoved the interferes effectively.Laboratory simulation wastewater results showed NO3-wasthe main interfering ion for cyanide derermination, it may due to NO3-can react with carbonand produce new CN-.NO3-in the process of cyanide in sample pretreatment can cause resultshigher than the real cyanide concentration.Wastewater treatment plant experiments verified sample holding time, sample saved withor without headspace, preprocessing steps have influences on cyanide determination for finaleffluent.Samples having completely pretreated preserved with no headspace measure cyanideimmediately,the results can get closer to real value.