Research on the effects of ferric salt added into aeration tank for phosphorus removal on biochemical system

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.

Conditioning of raw sludge and thermally hydrolyzed sludge by ferric salt and cationic polyacrylamide: rheological analysis

In this study, the conditioning effect of cationic polyacrylamide(CPAM) with different charge densities on raw sludge(RS) and thermo-hydrolyzed sludge(HS) pretreated with or without ferric salt is studied through orthogonal experiments. In addition, this paper uses the principles of rheology and morphology to analyze and clarify the conditioning mechanism of RS and HS, and reveals the mechanism of thermal hydrolysis to improve the dewatering performance of sludge.Compared with the RS, the HS has smaller particle size, better filterability, stronger fluidity and more obvious thixotropy. However, due to the influence of filter pressing time, ferric salt should be added before conditioning. Orthogonal experiment shows that the optimal conditioner is CPAM with charge density of 60, and the specific resistance to filtration(SRF) and capillary sunction time(CST) of the adjusted thermo-hydrolyzed sludge are reduced to (1.11 ± 0.07) × 1012 m/kg and 16.1 ± 1.8 s, the particle size increased from 61.2 to 253.5 μm.The moisture content of the sludge cake is about 48%. The structural strength and thixotropy of HS are higher than those of the RS, and can be greatly improved by adding ferric salt. Morphological analysis confirms that thermal hydrolysis can lyse microbial cells in sludge, and the sludge treated with ferric salt will have more porous structure and stronger flocculation strength.

A One-pot Thermal Decomposition of Commercial Organometallic Salt to Fe2O3@C-N and MnO@C-N for Lithium Storage

Iron oxide (Fe2O3) nanoparticles encapsulated by N-doped carbon framework (Fe2O3@C-N) were synthesized via a one-step thermal decomposition of the commercial C10H12FeN2NaO8 (ethylenediaminetetraacetic acid monosodium ferric salt), which can be served...

Effects of Ferric Salt of Different Forms on Phosphorus Removal

<p>This paper has studied phosphorus removal effects of ferric chloride (ionic state), polyferric chloride (polymer state) and ferric hydroxide (gel state) on the effluent of a municipal sewage treatment plant. The total phosphorus (TP) in the effluent was 1.74 mg·L-1. Results showed that ferric chloride was the best phosphorus remover among the three forms of ferric salt coagulants. With a dosage of 40 mg·L-1, its phosphorus removal rate could reach 90% and TP in the treated wastewater was reduced to less than 0.17 mg·L-1. After the treatment, the effluent quality met the first level A criteria in the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB18918-2002). At the same doage of 40 mg·L-1, the phosphorus removal rates of polyferric chloride and ferric hydroxide were 62% and 59%, respectively, lower than the rate of ferric chloride.</p>