Ping Zeng

Nutrients removal and recovery from anaerobically digested swine wastewater by struvite crystallization without chemical additions

Anaerobically digested swine wastewater contains high concentrations of phosphorus (P) and nitrogen (N). A pilot-scale experiment was carried out for nutrients removal and recovery from anaerobically digested swine wastewater by struvite crystallization. In the pilot plant, a sequencing batch reactor (SBR) and a continuous-flow reactor with struvite accumulation devices were designed and employed. The wastewater pH value was increased by CO(2) stripping, and the struvite crystallization process was performed without alkali and Mg(2+) additions. Results of the long-term operation of the system showed that, both reactors provided up to 85% P removal and recovery over wide ranges of aeration times (1.0-4.0 h), hydraulic retention times (HRT) (6.0-15.0 h) and temperatures (0-29.5°C) for an extended period of 247 d, in which approximate 30% of P was recovered by the struvite accumulation devices. However, 40-90% of NH(4)(+)-N removed was through air stripping instead of being immobilized in the recovered solids. The recovered products were detected and analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD) and chemical methods, which were proved to be struvite with purity of more than 90%. This work demonstrated the feasibility and effects of nutrients removal and recovery from anaerobically digested swine wastewater by struvite crystallization without chemical additions.

Combination of upflow anaerobic sludge blanket (UASB) and membrane bioreactor (MBR) for berberine reduction from wastewater and the effects of berberine on bacterial community dynamics.

Berberine is a broad-spectrum antibiotic extensively used in personal medication. The production of berberine results in the generation of wastewater containing concentrated residual berberine. However, few related studies up to date focus on berberine removal from wastewaters. In this study, a lab-scale upflow anaerobic sludge blanket (UASB)-membrane bioreactor (MBR) process was developed for berberine removal from synthetic wastewater. The performance of the UASB-MBR system on berberine, COD and NH(4)(+)--N removal was investigated at different berberine loadings. And the effects of berberine on bacterial communities were evaluated using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Results showed that, as the increase of berberine loadings, UASB performance was affected remarkably, whereas, efficient and stable performance of MBR ensured the overall removal rates of berberine, COD and NH(4)(+)--N consistently reached up to 99%, 98% and 98%, respectively. Significant shifts of bacterial community structures were detected in both UASB and MBR, especially in the initial operations. Along with the increase of berberine loadings, high antibiotic resisting species and some functional species, i.e. Acinetobacter sp., Clostridium sp., Propionibacterium sp., and Sphingomonas sp. in UASB, as well as Sphingomonas sp., Methylocystis sp., Hydrogenophaga sp. and Flavobacterium sp. in MBR were enriched in succession.

Phosphorus recovery from fosfomycin pharmaceutical wastewater by wet air oxidation and phosphate crystallization

Fosfomycin pharmaceutical wastewater contains highly concentrated and refractory antibiotic organic phosphorus (OP) compounds. Wet air oxidation (WAO)-phosphate crystallization process was developed and applied to fosfomycin pharmaceutical wastewater pretreatment and phosphorus recovery. Firstly, WAO was used to transform concentrated and refractory OP substances into inorganic phosphate (IP). At 200°C, 1.0MPa and pH 11.2, 99% total OP (TOP) was transformed into IP and 58% COD was reduced. Subsequently, the WAO effluent was subjected to phosphate crystallization process for phosphorus recovery. At Ca/P molar ratio 2.0:1.0 or Mg/N/P molar ratio 1.1:1.0:1.0, 99.9% phosphate removal and recovery were obtained and the recovered products were proven to be hydroxyapatite and struvite, respectively. After WAO-phosphate crystallization, the BOD/COD ratio of the wastewater increased from 0 to more than 0.5, which was suitable for biological treatment. The WAO-phosphate crystallization process was proven to be an effective method for phosphorus recovery and for fosfomycin pharmaceutical wastewater pretreatment.

Response Surface Optimization of Trace Element Requirement for the Production of Volatile Fatty Acids from Excess Sludge

Anaerobic microorganisms involved in VFAs fermentation have inherent requirements for trace metals. It is inferred that excess sludge contains inadequate amounts of bioavailable trace metals for high-rate VFAs fermentation. The unavailability of these trace metals is probably the primary reason of poor yield without any other obvious reason. However, trace metal requirements in VFAs fermentation are not often reported in literature. Therefore, minimum requirements for trace metals including Zn, Co, Cu, Fe and Mn in VFAs fermentation from excess sludge were investigated. Firstly, the effect of each trace metal element on the VFAs production was investigated, respectively. And then, response surface methology was employed to optimize the requirement conditions of these five trace elements. The results showed that these five metal elements had the potential to enhance the production of VFAs, and the improved influences were as follows: Fe > Co > Mn > Cu > Zn. However, the production of VFAs decreased obviously with a further increase of each trace element. The optimal mixed conditions of these five trace elements were found to be 0.0982% Fe, 0.0047% Co, 0.0053% Zn, 0.0038% Cu and 0.0936% Mn. Under the optimal conditions, the concentration of VFAs reached 8410 mg/L, and increased by 2.5 times compare with the control. Finally, the consistent results between the prediction and the experiment indicated that the established polynomial model was feasible, and VFAs production could be described well by this model.

The Cultivation of Mixed Microalgae and CO2 Fixation in a Photo-Bioreactor

Microalgae is a form of prospective biomass energy. Cultivation of wild mixed microalgae is not only develop a new way for biomass energy production, but reduce the emission of carbon dioxide in flue gas, which is important to the alleviation of global climate change. In this study, wild mixed microalgae were cultivated in an airlift photo reactor. The effects of carbon oxide concentration, condition of illumination on growth of microalgae as well as the crude fat content in microalgae were investigated during 180 days cultivation. And the kinetic parameters of mixed microalgae were tested. The results showed that the microalgae growth rate could be greatly enhanced by feeding with CO2 of flue gas. The growth rate of microalgae feeding with 10% CO2 was four times of that feeding with air. Continuous illumination for 24 hr is beneficial for microalgae growth and stability of growth rate. The specific growth rate reached to 0.2 1/d, which was higher than that conditions of half illumination in one day. In the condition of same microalgae biomass and total photosynthetic active radiation, the accumulation of crude fat would benefit from decrease of radiation intensity and increase of light time. The CO2 absorption by mixed microalgae obeyed the first order kinetics. The reaction constant was 0.015 1/min at the microalgae concentration of 1 g/L.

Nitrogen Removal Potential and Biofilm Characteristics in the Anaerobic Ammonium Oxidation ('ANAMMOX') Biofilter Reactor

The effects of influent substrate concentration load, hydraulic load and total nitrogen load on total nitrogen removal rate were compared in an up-flow ANAMMOX bio-filter reactor. The deep region division and bacterial distribution in the ANAMMOX bio-film were deduced based on the theory of micro-environment and the existence of substrate transfer gradient. In addition, the composition and distribution model was obtained for the bio-film. The results showed that the maximum nitrogen removal rate in the ANAMMOX reactor increased linearly as the increasing of influent substrate concentration load, hydraulic load and total nitrogen load, respectively. The results indicated that the maximum of nitrogen removal rate, influent hydraulic load and substrate concentration of c(NH4+-N+NO2--N) were 12 kg/(m3•d), 4.79 m3/(m2•h) and 240 mg•L-1, respectively. The micro-environment of the biofilm, portrait grads distribution of the nitrite concentration along the depth of biofilm and the high ground amount of the biomass made the nitrite resistibility increase up to 130 mg•L-1. The biomembrane system include biofacies and micro-environment were extraordinary complicated since it affected by some factors such as the inoculum of biofilm, influent organic matters concentration, dissolved oxygen concentration, mass transfer capability of biofilm and micro-environment in the bioreactor.

The Characteristics of Aerobic Granules Cultivated with the Effluent from an Anaerobic Baffled Reactor for Berberine Wastewater Treatment

In this study, aerobic granular sludge was cultivated with the effluent of anaerobic baffled reactor (ABR) which degraded berberine wastewater. After 80-day operation, stable granules with sizes of 2-10 mm were obtained. With the granulation, the SVI value decreased from 120 to 20.34 mL/g. The granular sludge had an excellent settling ability with the settling velocity over 104 m/h. Aerobic granular sludge exhibited good performance for organics and berberine removals from the effluent of ABR. After granulation, high and stable removal efficiencies of 90.47% for COD, 64.32% for berberine, were achieved with the volumetric exchange ratio of 50% and cycle duration of 6 h. The average COD and berberine of the effluent were 171.1mg/L and 3.88mg/L, after aerobic granules matured.

Phosphorus Releasing from Surplus Activated Sludge by Ultrasonic Pretreatment

Three kinds of surplus activated sludge were pretreated by alkali and combination of alkali and ultrasonic. The changes of PO43-P, TP, SCOD, TOC, TS, VS before and after pretreatment were investigated. The results showed that phosphorus and organic matter could be released into supernatant both by alkali and ultrasonic. The surplus activated sludge from municipal wastewater treatment plant was easier to be broken than that from pharmaceutical wastewater treatment plant. The activated sludge from Qinghe wastewater treatment plant could be selected for further phosphorus recovery since the largest quantity of phosphorus release and the lowest organic matter release ratio among the three kinds of surplus activated sludge.

The Comparison Study of Four Lab Scale Microalgae Collection Ways

Microalgae are a form of prospective biomass energy. Cultivation of wild mixed microalgae not only develop a new way for biomass energy production, but reduce the emission of carbon dioxide in flue gas, which is important to the alleviation of global climate change. The production of bio-flues using microalgae included microalgae cultivation, harvesting and product post-treatment. The cost-effective microalgae harvesting ways was beneficial for all the production process. This study was carried out on the basis of microalgae cultivation. The microalgae collection ways including centrifuge, filtration by slow filter paper, 13# and 25# plankton net were compared, the results showed that, the algae cell collection efficiency decreased as follows, centrifuge > filtration by slow filter paper >25# plankton net>13# plankton net. For the same collection way, the collection efficiency had a little difference according to different microalgae species. The most suitable collection way was centrifuge for the microalgae cultivation in lab.

Adsorption Characteristics of Cu2+ onto Zeolite from Pharmaceutical Industrial Wastewater

The adsorption of Cu2+ from pharmaceutical wastewater by zeolite was studied in a batch adsorption system. Factors inflflflfluencing copper adsorption such as pH (1-5), adsorbent dosage (5-50 g/L) and contact time (20-600 min)were investigated. The equilibrium of adsorption process was established in about 480 min, while pH was 5 and adsorbent dosage was 30 g/L. After the adsorption equilibrium was achieved, the removal efficiency of Cu2+ was above 99%. Acomparison of the kinetic models on the overall adsorption rate showed that the adsorption system was best described by the pseudo second-order kinetics. The adsorption equilibrium datafifififit best with the Langmuir isotherm.