Jingqing Gao

Municipal wastewater treatment via co-immobilized microalgal-bacterial symbiosis: Microorganism growth and nutrients removal

A symbiotic microalgal-bacterial system may be an optional technology for wastewater treatment. In this study, co-immobilized of a bacterium isolated from a municipal wastewater treatment plant (Pseudomonas putida) and a microalgae Chlorella vulgaris was used in the study of cell growth and nutrient removal during wastewater treatment under batch and continuous culture conditions. Under batch culture conditions, co-immobilization treatment significantly increased the cell density of C. vulgaris and P. putida compared with other treatments. The co-immobilized treatment also showed higher removal of ammonium, phosphate and COD than any single treatment, indicating that the nutrient uptake capability of C. vulgaris and P. Putida was mutually enhanced mutually. When tested in continuous mode, the treatment with a hydraulic retention time of 24h at the organic load rate of 1159.2mgCODL-1d-1 was most appropriate for wastewater treatment.

Phosphorus Removal from Continuous Phosphate-Contaminated Water by Electrocoagulation using Aluminum and Iron Plates Alternately as Electrodes

The objective of this study was to investigate the effects of the main parameters on phosphate removal from continuous phosphate-contaminated water by electrocoagulation based on removal rate and system energy consumption. In the experiment, aluminum and iron plates were used as alternate electrodes and experiment parameters included initial phosphate concentration, current density, flow rate, and initial pH. The results indicated that increases of initial phosphate concentration and flow rate had reduced removal rate and energy consumption. Removal rate and system energy consumption increased by increasing current density. The maximum removal efficiency of 90% was obtained at flow rate 40 mL/min. The minimum energy consumption was 0.165 kWh/m3 at flow rate 100 mL/min. With the increase of initial pH from 4 to 8, the removal rate increased and energy consumption decreased. When the pH was above 8, the removal rate decreased and energy consumption increased. The maximum removal efficiency of 92% and minimum energy consumption of 0.191 kWh/m3 were obtained at pH 8.

Bioleaching in batch tests for improving sludge dewaterability and metal removal using Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans after cold acclimation

Bioleaching is a promising technology for removal of metals from sludge and improvement of its dewaterability. Most of the previous studies of bioleaching were focused on removal of metals; bioleaching in cold environments has not been studied extensively. In this study, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were acclimated at 15 °C and co-inoculated to explore the optimal conditions for improvement of sludge dewaterability and removal of metals by the sequencing batch reactors. The data show after 6 days of bioleaching at 15 °C, 89.6% of Zn, 72.8% of Cu and 39.4% of Pb were removed and the specific resistance to filtration (SRF) was reduced to ∼12%. In addition, the best conditions for bioleaching are an initial pH of 6, a 15% (v/v) inoculum concentration, and A. thiooxidans and A. ferrooxidans mixed in a ratio of 4:1. We found that bioleaching of heavy metals is closely related to final pH, while the sludge SRF is dominated by other factors. Bioleaching can be completed in 6 days, and the sludge dewaterability and removal of metals at 15 °C meet the requirements of most sewage treatment plants.

Peroxidation damage and antioxidative capability of Ceratophyllum demersum under

The current article investigated the effects of ammonia nitrogen concentration and pH on peroxidation damage and antioxidative capability of Ceratophyllum demersum. The pH ranges (7 and 9) were carefully controlled to distinguish between the effects of unionized ammonia (NH3) and ionized ammonia ( ). The addition of ammonia significantly decreased chlorophyll a content. Peroxidase and superoxide dismutase activities as well as glutathione content under high ammonia conditions (10 mg N/L) significantly increased at pH 7 but were no different or reduced at pH 9. Catalase activity as well as ascorbic acid and malondialdehyde contents significantly increased under all ammonia treatments at pH 7 and 9. C. demersum suffered from stress at pH 9 under high ammonia conditions. Higher pH in water may induce C. demersum to exhibit more severe physiological responses.

Studies on modified conditions of biochar and the mechanism for fluoride removal

AbstractThe modified Mongolian scotch pine tree sawdust char (MMSC), fabricated from the natural Mongolian scotch pine tree sawdust char (MSC) using phosphoric acid-microwave method, was used as the F− adsorbent of aqueous solution. MMSC was prepared according to the optimized method as follows. MSC and 25% (vol) phosphoric acid (v/v = 1:4) were mixed in Bunsen beaker at 25°C for 24 h. The mixer was then radiated for 3 min (Radiation power 630 W), followed by filtration, generating the desired MMSC, which was washed with distilled water until the pH reached around 7.0, and then dried in an oven at 50°C till constant weight for further fabrication. No obvious difference of MMSC and MSC was observed in color. The adsorption capacity of MMSC reached 885 mg kg−1 for F− in high-fluoride resource water. The concentration was reduced to below the recommended value (1.5 mg L−1) from the concentration of 20 mg L−1 when the high dosage of MMSC was used. Compared with MSC, the MMSC can be used as potential F− adsorb...

Enhanced removal of chemical oxygen demand, nitrogen and phosphorus using the ameliorative anoxic/anaerobic/oxic process and micro-electrolysis.

Synthetic wastewater was treated using a novel system integrating the reversed anoxic/anaerobic/oxic (RAAO) process, a micro-electrolysis (ME) bed and complex biological media. The system showed superior chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) removal rates. Performance of the system was optimised by considering the influences of three major controlling factors, namely, hydraulic retention time (HRT), organic loading rate (OLR) and mixed liquor recirculation (MLR). TP removal efficiencies were 69, 87, 87 and 83% under the HRTs of 4, 8, 12 and 16 h. In contrast, HRT had negligible effects on the COD and TN removal efficiencies. COD, TN and TP removal efficiencies from synthetic wastewater were 95, 63 and 87%, respectively, at an OLR of 1.9 g/(L·d). The concentrations of COD, TN and TP in the effluent were less than 50, 15 and 1 mg/L, respectively, at the controlled MLR range of 75-100%. In this system, organics, TN and TP were primarily removed from anoxic tank regardless of the operational conditions.

Improvement of sewage sludge dewaterability by bioleaching in a continuous plug flow bioreactor: optimization of process parameters

A novel process for sewage sludge bioleaching by mixed Thiobacilli (Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans) using a 12-stage, 180 L working volume continuous plug-flow bioreactor, is presented. The objective of the present study was to assess the impact of some parameters on the sludge dewaterability and to improve the sludge dewaterability by optimization of these parameters. The parameters examined were sludge moisture content, nutrients dosage, aeration rate, and the number of reactors. The order of the influence of these factors on sludge dewaterability was found to be sludge moisture content > nutrients dosage > aeration rate > number of reactors. The optimized conditions were: sludge moisture content, 98.0%, nutrients dosage, 9 g/L, aeration rate, 8 m3/h, and 10 reactors. Confirmation experiments conducted under optimum conditions demonstrate the sludge dewaterability to be remarkably improved. After 2 days of bioleaching, the moisture of bioleached sludge cake was reduced to below 60%.

Enhancing dewaterability of sewage sludge by the application of tween-20 during bioleaching: Performance evaluation and mechanistic study

ABSTRACT Dewatering is recognized as an important method for treating sewage sludge before its disposal. In this paper, the nonionic surfactant Tween-20 was used for the first time to improve the dewaterability of sewage sludge during bioleaching. The specific resistance to filtration (SRF), water content (WC) and bound water content (BW) of the sludge cake were used to evaluate sludge dewaterability. The results indicated that a 1 g/L Tween-20 dosage with an inoculum ratio of 20%, a S0 dosage of 2 g/L and a FeSO4 · 7H2O dosage of 10 g/L provided oxidation efficiencies up to 100% for Fe2+ and 65.8% for S0. The SRF of the bioleached sludge decreased to as low as 0.81 × 1012 m/kg from the initial 12.6 × 1012 m/kg for raw sludge. A WC of 47.16% was achieved while 48.1% of BW was released during bioleaching. The results from this study indicate that adding of an appropriate amount of Tween-20 to sewage sludge is a promising method to enhance dewaterability by bioleaching.

Use of Chitosan-modified Bentonite for Removal of Cu 2+ , Cl − and 2,4-Dichlorophenoxyacetic Acid (2,4-D) from Aqueous Solution

Water pollution and its treatment to avail safe drinking water is a major concern of the 21st century.1 Various treatment methods have been developed for decontamination purposes, such as adsorption, coagulation, precipitation, filtration, electrodialysis, membrane separation.2 Adsorption is recognized as one of the most effective processes for the removal of Cu2+, Cl−, and 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions in the above mentioned techniques.3

Contaminant removal performances on domestic sewage using modified anoxic/anaerobic/oxic process and micro-electrolysis

The objective of this study was to enhance removal of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) from domestic sewage in a sequencing batch reactor with added new materials. A modified anoxic/anaerobic/oxic (MAAO) process, integrating a micro-electrolysis (ME) bed in an anoxic tank, and complex biological media (CBM) in anoxic, anaerobic and oxic tanks to treat domestic sewage, and their performances were investigated. The MAAO system was operated at controlled hydraulic reTENTion time (HRT) of 8 h and mixed liquor recirculation (MLR) at 75%. The results showed that the MAAO system could effectively remove COD, TN and TP with average rates of 93%, 80% and 94%, respectively, in March, and 94%, 76% and 91%, respectively, in August. In this system, TP was primarily removed from the anoxic tank regardless of the operational conditions; removal contribution ratios to TP of the anoxic tank reached 56% both in March and August, indicating that the ME bed can effectively enhance phosphorus removal. TN was primarily removed from the anoxic and anaerobic tanks; removal contribution ratios to TN of anoxic and anaerobic tanks reached 36–38% and 37–38%, respectively. The oxic tank had the highest share of COD removal (56% both in March and August) in the removal of phosphorus. The outflow concentrations of COD, TN and TP were 3–46, 7–14 and 0.3–0.5 mg/L, respectively, in March, and 26–49, 9–15 and 0.04–0.1 mg/L, respectively, in August. COD and TN removal performances indicated that the innovative materials of the ME bed and CBM can effectively enhance COD and TN removal.