Shoubin Zhang

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.

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...

Influence of free chlorine on nitrite accumulation in biological aerated filter(BAF)

The influence of free chlorine on the nitrite accumulation in Biological Aerated Filter (BAF) was investigated by adding chlorine in the bioreactor in order to carry out a shortcut nitrification-denitrification. The relationship of the adding dosage and feeding modes of free chlorine and the nitrite accumulation in BAF were also considered. The results show that the nitrite accumulation could be achieved by adding chlorine. When the influent concentration of chlorine was 4mg/L, the concentration of effluent nitrite nitrogen was increased remarkably after the system had been operated for 20 days, and the nitrite accumulation rate could be kept in 60%–70%. The steady state of nitrite accumulation could be maintained with decreasing in the concentration of the influent chlorine, and could also be maintained at a certain degree with the adding mode of intermittent chlorination.

Influence of influent pH value on nitrite accumulation in a biological aerated filter (BAF)

Influence of the pH value of influent on the nitrite accumulation was investigated in a biological aerated filter (BAF) operated in normal conditions. The removal efficiency of ammonia nitrogen and the performance of nitrite accumulation in the BAF were also discussed. The results showed that the ammonia nitrogen removal in BAF was heavily influenced by the influent pH value. Drastically fluctuating of the influent pH value was not conducive to the removal of ammonia nitrogen but beneficial to the nitrogen accumulation. It was found that the continuous rising of pH value could hinder the activity of ammonia oxidizing bacteria to adapt alkaline environment, and there were approximately 77.2% and 88% of ammonia nitrogen were removed in the middle and the upper part of filter bed respectively. It was considered that the nitrite accumulation could be induced in BAF by simply adjusting the influent pH value, but the situation of a long-term and stable formation of nitrite accumulation would get out of hand, at the same time, the removal efficiency of ammonia nitrogen would not high and unstable.

Comparative Study of Different Activated Slags on Phosphate Removal

A comparative study on phosphate removal between activated steel slag and blast furnace slag was investigated. The efficiency of different slags before and after activated for phosphate removal were also evaluated. The results show that the slags activated by hydrothermal treatment are more efficient than raw slags in phosphate removal. The activated slags could be reused for several times and the phosphate removal efficiency could be guaranteed by increasing there action time towards to different reused times. Compared with activated pulverized slags, the activated granular slags could be reused for a longer time for a given initial phosphate concentration. The results suggest that the activated granular slags may be effective materials for phosphate removal. The phosphate removal by activated slag was mainly through chemical precipitation.

Parameter optimization and performance of backwashing in biological aerated filters

The backwashing optimization, which included gas washing, water washing and water rinsing, was carried out in three biological aerated filters with zeolite, ceramic particle and carbonate media. The recovery of headloss and treatment efficiency in the biofilters after backwashing were also investigated for deeper understanding of the relationship of headloss and backwashing in BAF. The results showed that the COD and SS increased in effluent just after backwashing but could be recovered in 2 hours. The concentration of ammonia nitrogen in effluent almost did not change and recovered quickly. All of three BAFs have a promising backwashing performance and operational stability after backwashing. The backwashing procedure of upfollow BAF is suggested as follow: Firstly, air washing 2–3min with air flow rate of 10 L m⁻² s⁻¹, then air and water washing 3–5min with both air and water flow rate of 10 L m⁻² s⁻¹, and finally water rinsed for 9–11min with water flow rate of 10 L m⁻² s⁻¹.