Liping Qiu

Performances and nitrification properties of biological aerated filters with zeolite, ceramic particle and carbonate media

The performance and nitrification properties of three BAFs, with ceramic, zeolite and carbonate media, respectively, were investigated to evaluate the feasibility of employing these materials as biological aerated filter media. All three BAFs shown a promising COD and SS removal performance, while influent pH was 6.5-8.1, air-liquid ratio was 5:1 and HRT was 1.25-2.5 h, respectively. Ammonia removal in BAFs was inhibited when organic and ammonia nitrogen loading were increased, but promoted effectively with the increase pH value. Zeolite and carbonate were more suitable for nitrification than ceramic particle when influent pH below 6.5. It is feasible to employ these media in BAF and adequate bed volume has to be supplied to satisfy the requirement of removal COD, SS and ammonia nitrogen simultaneously in a biofilter. The carbonate with a strong buffer capacity is more suitable to treat the wastewater with variable or lower pH.

An approach for phosphate removal with quartz sand, ceramsite, blast furnace slag and steel slag as seed crystal

The phosphate removal abilities and crystallization performance of quartz sand, ceramsite, blast furnace slag and steel slag were investigated. The residual phosphate concentrations in the reaction solutions were not changed by addition of the ceramsite, quartz sand and blast furnace slag. The steel slag could provide alkalinity and Ca(2+) to the reaction solution due to its hydration activity, and performed a better phosphate removal performance than the other three. Under the conditions of Ca/P 2.0, pH 8.5 and 10 mg P/L, the phosphate crystallization occurred during 12 h. The quartz sand and ceramsite did not improve the phosphate crystallization, but steel slag was an effective seed crystal. The phosphate concentration decreased drastically after 12 h after addition of steel slag, and near complete removal was achieved after 48 h. The XRD analysis showed that the main crystallization products were hydroxyapatite (HAP) and the crystallinity increased with the reaction time. Phosphate was successfully recovered from low phosphate concentration wastewater using steel slag as seed material.

Domestic wastewater treatment using biological aerated filtration system with modified zeolite as biofilm support

AbstractModified zeolite and natural clinoptilolite were applied to treat domestic wastewater in two two-stage up-flow biological aerated filters (BAF) to compare their abilities to act as biofilm supports. The results showed that the two-stage BAF with modified zeolite brought a relative superiority to natural clinoptilolite two-stage BAF in terms of chemical oxygen demand and ammonia nitrogen removal under the conditions of temperature 20–26°C and dissolved oxygen above 4.00xa0mgu2009l−1. In addition, the detection of the amount of heterobacteria and nitrobacteria of two two-stage BAFs also showed that modified zeolite medium was more suitable to the attached growth of nitrobacteria, which is helpful to the improvement of nitrification performance in two-stage BAF with modified zeolite.

The characteristics and effect of grain-slag media for the treatment of phosphorus in a biological aerated filter (BAF)

Abstract Haydite and grain-slag, a new type of filter media made of grain slag, were used as filter media for biological aerated filter (BAF) to treat synthetic wastewater in parallel. The aim of this study was to compare the phosphorus removal performance of two BAF reactors at the different influent pH values, hydraulic retention time (HRT), and phosphorus load rates. It demonstrated that the BAF packed with grain-slag showed higher phosphate removal efficiency than with haydite. The removal of phosphate by the grain-slag BAF was in the range of 75.21–84.98%; 63.10–70.44%; 40.49–48.02%; and 26.10–33.11%, respectively, under the HRT of 12, 8, 5, and 1u2009h. The results obtained from the study of phosphate removal rate vs. pH values indicated that grain-slag BAF could remove phosphorus effectively by biologically induced chemical precipitation and the sediments do not affect the effluent turbidity.

Phosphate removal through crystallization using hydrothermal modified steel slag-based material as seed crystal

AbstractA novel steel slag-based material (SSM) was prepared, based on the powdered steel slag and modified by hydrothermal treatment to improve its activity for phosphate removal. The phosphate removal and recovery with the SSM and the modified steel slag-based material (MSSM) as seed crystal were evaluated, and the reuse performance of the MSSM was investigated. The results showed that the hydration activity of the MSSM could be improved by hydrothermal modification, which might be attributed to the releasing of OH− and Ca2+ from MSSM after the hydrothermal treatment is in favor of the calcium phosphate crystallization. The MSSM as a seed crystal could be used repeatedly about 20 times in this experiment, and the residual phosphate concentrations were all below 0.5u2009mg/L with the initial concentration of 10u2009mg/L. The X-ray diffraction pattern of the reaction products revealed that the crystallinity of the products increased with increasing reaction time and the diffraction peaks well matched with that of...

Study on Stability and Influencing Factors of Nitrite Accumulation in Biological Aerated Filter

Study was made on stability and influencing factors of nitrite accumulation in Biological Aerated Filter (BAF)treating simulated municipal wastewater. The possibility of shortcut nitrification–denitrification in low ammonia wastewater treatment was discussed. The mode of natural start-up was favorable to the nitrite accumulation in BAF and the highest nitrite accumulation rate was over 80%. By adjusting pH, nitrite accumulation can take place in BAF. When the influent pH value was 6.5 to 7, the highest nitrite accumulation rate was 57%. But long-term stable nitrite accumulation cannot be obtained only through changing influent pH value. The lower concentration of DO was of advantage to the formation of the nitrite accumulation. When the concentration of DO was controlled to less than 0.5 mg/L, the nitrite accumulation rate can improved significantly to the maximum over 80%. The increasing of hydraulic loading can contribute to nitrite accumulation. When the hydraulic loading was enhanced to 10 m3/(m2•h), the average nitrite accumulation rate can be increased by 52.5 times. The increasing of influent ammonia loading cannot improve nitrite accumulation notably. When influent pH was 6.5 to 7, concentration of DO was 1.0 to1.5 and the filtration rate was 5 m/h, the nitrite accumulation of BAF reactor was of good stability. During 60 days running, the nitrite accumulation can keep at 65% to 75% stably and obvious shortcut nitrification-denitrification was found.

The Effect of Salinity on Membrane Fouling Characteristics in an Intermittently Aerated Membrane Bioreactor

The effect of salinity on the membrane fouling characteristics was investigated in the intermittently aerated membrane bioreactor (IAMBR). Five different salinity loadings were set from 0 to 35u2009g·L−1 (referring to NaCl), respectively. The removal of total organic carbon (TOC) and ammonia-nitrogen (-N) was gradually decreased with increasing salinity. The variation of membrane filtration resistance, particle size distribution (PSD), extracellular polymeric substances (EPS), soluble microbial products (SMP), and relative hydrophobicity (RH) analysis revealed that salinity has a significant effect on sludge characteristics in IAMBR. The results also indicated that the membrane fouling is often caused by the integration of sludge characteristics in saline wastewater.

Optimization of Crystallization of Magnesium Ammonium Phosphate: Initial Phosphate Concentration, PH and Reactants Molar Ratio

By- products are widespread in the crystallization of magnesium ammonia phosphate (MAP) as the differences in reactive conditions which effects the forms and habits of crystals. The study focused on the supernatant from septic tank in order to achieve in-situ treatment. Based on the effluent, the optimization research of initial phosphate concentration and pH was investigated by using single factor analysis. The crystal products with different reaction condition were also characteristiced through the XRD analysis. The experimental results showed that the optimum reactants molar ratio of n(NH4+):n(Mg2+):n(PO43-) were 90:25:1, 4:1.6:1 and 3:1.4:1 when pH value was 9.5 with initial phosphate concentration 8mg/L, 50mg/L and 100mg/L, respectively. It was also observed that the phosphate removal rate increased with increasing the initial phosphate concentration or pH value. As the aging time increased, the removal rate was in parabolic curve with 30 minute at the highest point. The XRD analysis revealed that the best MAP crystal could be produced with initial phosphate concentration 50mg/L and pH 9.0.

Effect of power ultrasound on crystallization characteristics of magnesium ammonium phosphate

Magnesium ammonium phosphate (MAP) crystallization could be utilized for the recovery of phosphorus from wastewater. However, the effectiveness of the recovery is largely determined by the crystallization process, which is very hard to be directly observed. As a result, a specific ultrasonic device was designed to investigate the crystallization characteristics of MAP under various ultrasonic conditions. The results demonstrated that the metastable zone width (MZW) narrowed along with the rising of the ultrasonic power. Similarly, for the 6mM MAP solution, with the ultrasonic power gradually enhanced from 0W to 400W, the induction time was shortened from 340s to 38s. Meanwhile, the crystallization rate was accelerated till the power reached 350W, and then remained a constant value. It can be observed from the scanning electron microscopy (SEM), the MAP crystal became bigger in size as well as the crystal size distribution (CSD) became broad and uneven, with the increase of ultrasonic power. The results indicate that the crystallization process enhanced by power ultrasound could be used as an effective method to eliminate and recover the phosphorus from wastewater.

Phosphate Removal and Recovery with Seed Crystals in Low Concentrated Phosphate Wastewater

The phosphate removal and recovery from lower concentrated phosphate wastewater with the quartz sand, ceramsite, blast furnace slag and steel slag as seed crystals were investigated. The results showed that the steel slag performed a better phosphate removal performance than the other threes. The phosphate crystallization occurred under the reaction conditions of Ca/P 2.0, pH 9.0, phosphate concentration 10 mg/L and reaction time 12h. The steel slag could be employed as an effective seed crystal, of which the phosphate concentration decreased drastically in 12h and almost had been removed completely in 48h. The XRD analysis showed that the main crystallization products were hydroxyapatite (HAP) and the crystallinity increased with the reaction time.