Quan Feng

Enhanced coagulation of ferric chloride aided by tannic acid for phosphorus removal from wastewater.

Phosphorus removal from wastewater is of great importance. In the present study, ferric chloride was selected as the coagulant, and tannic acid (TA), a natural polymer, as the coagulant aid to develop an effective coagulation process with the emphasis of phosphorus recovery from different types of wastewater. The results showed that TA can accelerate the settling speed by forming flocs with large size, reduce the residual Fe(III) to eliminate the yellow color caused by Fe(III), and slightly increase the phosphorus removal efficiency. The precipitate formed by TA-aided coagulation showed the advantage of releasing phosphorus faster than ferric phosphate, indicating the possibility of phosphorus recovery from wastewater as slow release fertilizer. To further understand the structural characteristics of the precipitate, analytical techniques such as Raman spectroscopy, X-ray photoelectron spectroscopy and matrix-assisted laser desorption ionization-time of flight mass spectrometry were employed. The analytical results indicated that TA-Fe-P complex was formed during the coagulation/flocculation processes. Solid phase in the precipitate consisted of TA-Fe-P complex, Fe-TA complex and/or ferric hydroxyphosphate.

Effects of packing rates of cubic-shaped polyurethane foam carriers on the microbial community and the removal of organics and nitrogen in moving bed biofilm reactors

The effects of packing rates (20%, 30%, and 40%) of polyurethane foam (PUF) to the removal of organics and nitrogen were investigated by continuously feeding artificial sewage in three aerobic moving bed biofilm reactors. The results indicated that the packing rate of the PUF carriers had little influence on the COD removal efficiency (81% on average). However, ammonium removal was affected by the packing rates, which was presumably due to the different relative abundances of nitrifying bacteria. A high ammonium removal efficiency of 96.3% at a hydraulic retention time of 5h was achieved in 40% packing rate reactor, compared with 37.4% in 20% packing rate. Microprofiles of dissolved oxygen and nitrate revealed that dense biofilm limits the DO transfer distance and nitrate diffusion. Pyrosequencing analysis of the biofilm showed that Proteobacteria, Bacteroidetes and Verrucomicrobia were the three most abundant phyla, but the proportions of the microbial community varied with the packing rate of the PUF carriers.

Application of combined physicochemical and biological processes for enhanced treatment of avermectin fermentation wastewater

This paper aimed at developing the enhanced biological treatment processes for treating avermectin fermentation wastewater (AFW). After UASB treatment and chemical coagulation, the pretreated AFW was subsequently flowed into a rCAA reactor (reactor with repeated coupling of aerobes and anaerobes using macroporous carriers) system for further pollutant degradation and excess sludge reduction. By the treatment with chemical coagulation, COD, total nitrogen and total phosphorus concentration of treated AFW were eliminated to 550-700 mg/L, 130-160 mg/L and 1 mg/L, respectively, and the dark color of the wastewater was greatly bleached. After this decolorized wastewater was treated by the following rCAA bioreactor, the COD could be reduced to around 200-300 mg/L, while the further decrease of COD less than 200 mg/L was difficult. The Biolog analysis and OUR test for the water treated by rCAA bioreactor demonstrated that the effluent from chemical coagulation contained some unknown compounds with low biodegradability and would simplify the microbial community in the subsequent rCAA reactor.