Abstract
Abstract In this paper, two iron salts, ferrous chloride (FeCl2) and ferric chloride (FeCl3), are directly added into an aeration tank for phosphorus removal, and their effects on the biochemical system are studied; the water quality parameters such as pH and alkalinity are also investigated. The extent of influence of the added iron salts on the pH and alkalinity of aerated solutions is demonstrated to be FeCl3 > FeCl2. When the dosage of iron ions is 20 mg/L, the decrease in pH and alkalinity caused by FeCl3 is 0.5 and 65 mg/L, which is higher than FeCl2 by 2% and 26%. The initial phosphorus removal effect of FeCl2 is worse than that of FeCl3, but after continued aeration and oxidation, the phosphorus removal effect of FeCl2 can be improved; however, the final phosphorus removal effect is basically the same as that of FeCl3 added directly. The results show that FeCl2 is preferred when iron salt is added directly into the aeration tank to remove phosphorus. The proposed scheme can reduce the effect of iron salts on the alkalinity of the biochemical system on the premise of ensuring the phosphorus removal effect of the system, and is conducive to ensuring the stable operation of the biochemical system.
Highlights
As the urbanisation process is expedited and people’s living standards have improved in China, the quantity of wastewater discharge is rising year by year [1], and the black odour water body and eutrophication are increasingly becoming a serious concern [2,3,4]
This paper mainly investigates the changes in pH, alkalinity and phosphorus removing effect after adding FeCl2 and FeCl3 into a solution, and studies the effects of FeCl2 and FeCl3 on the biochemical system of aeration tanks, so as to provide a reference for wastewater plants, which directly add coagulated phosphorus removing agents; this will enable us to select the appropriate phosphorus removing agent in upgrading standards and reconstruction projects
Activated sludge is the key to the effect of wastewater disposal in aeration tanks, while the pH value and alkalinity of aeration tanks are closely related to the survival, propagation and metabolic function of microorganisms [17,18,19]
Summary
As the urbanisation process is expedited and people’s living standards have improved in China, the quantity of wastewater discharge is rising year by year [1], and the black odour water body and eutrophication are increasingly becoming a serious concern [2,3,4]. If FeCl2 is directly added to aeration tanks, it will be transformed into FeCl3 under the oxidisation effect of aeration oxygenation This reduces the hydrochloric acid added and the agent preparation cost and prevents the effects of FeCl3 on the biochemical system. This paper mainly investigates the changes in pH, alkalinity and phosphorus removing effect after adding FeCl2 and FeCl3 into a solution, and studies the effects of FeCl2 and FeCl3 on the biochemical system of aeration tanks, so as to provide a reference for wastewater plants, which directly add coagulated phosphorus removing agents; this will enable us to select the appropriate phosphorus removing agent in upgrading standards and reconstruction projects
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