Wu Zhenbin

Application of constructed wetlands on wastewater treatment for aquaculture ponds

A group of constructed wetlands (CWs) were applied to the recirculating aquaculture system. This study assessed the performance of CWs in treating the aquaculture wastewater, examined the water quality condition of aquaculture ponds and the growth and the survival rate of “target” species (Ictalurus punctatus and Megalobrama amblycephala). The results showed that CWs were effective on reducing the concentrations of 5-day biochemical oxygen demand (BOD5, at 70.5%), total suspended solids (TSS, at 81.9%), chlorophyll a (Chl-a, at 91.9%), ammonium (NH4+, at 61.5%) and nitrate nitrogen (NO3−-N, at 68.0%). Effect of CWs on phosphate (PO43−-P) removal was relatively lower (at 20.0%). The concentrations of BOD5, TSS, Chl-a, NH4+ and TN, TP in the recirculating culture pond were significantly lower than that in the control pond(p < 0.05). CWs could help to increase total yield, survival rate of the “target” species and significantly decrease feed conversion ratio (p < 0.05).

Characteristics of the microbial communities in the integrated vertical-flow constructed wetlands

Microorganisms play an important role in removing pollutants from constructed wetlands. We investigated the microbial characteristics in a novel integrated vertical-flow constructed wetland (IVCW), which has been in operation in Wuhan, China since 1998. We used phospholipid fatty acid (PLFA) and amoA gene to analyze the structure and diversity of the microbial community within the IVCW. PLFA results suggested that the amount of bacterial PLFA was significantly higher than that of fungal PLFA, but the total microbial biomass represented by PLFA index was low in the system. Microbial spatial distribution showed significantly higher bacterial (both G+ and G-) and fungal biomass in the surface than in the subsurface layers. The ratios of monounsaturated to branched PLFA demonstrated that an anaerobic layer sandwiched by two aerobic layers existed in the IVCW, consistent with the redox potential results. Analysis of the amoA revealed the presence of Nitrosomonas-like sequences in the surface substrate of the downflow chamber and apparent diversities of ammonia-oxidizing bacteria in the system. These results suggest that microorganisms, despite their relatively low biomass, have inhabited the IVCW, and the results will offer some valuable information on microbe to system designers and managers.

Bacterial diversity in activated sludge from a consecutively aerated submerged membrane bioreactor treating domestic wastewater

The bacterial diversity of activated sludge from submerged membrane bioreactor (SMBR) was investigated. A 16S rDNA clone library was generated, and 150 clones were screened using restriction fragment length polymorphism (RFLP). Of the screened clones, almost full-length 16S rDNA sequences of 64 clones were sequenced. Phylogenetic tree was constructed with a database containing clone sequences from this study and bacterial rDNA sequences from NCBI for identification purposes. The 90.6% of the clones were affiliated with the two phyla Bacteroidetes (50%) and Proteobacteria (40%), and beta-, gamma-, and delta-Proteobacteria accounted for 7.8%, 28.1%, and 4.7%, respectively. Minor portions were affiliated with the Actinobacteria and Firmicutes (both 3.1%). Only 6 out of 64 16S rDNA sequences exhibited similarities of more than 97% to classified bacterial species, which indicated that a substantial fraction of the clone sequences were derived from unknown taxa. Rarefaction analysis of operational taxonomic units (OTUs) clusters demonstrated that 150 clones screened were still insufficient to describe the whole bacterial diversity. Measurement of water quality parameter demonstrated that performance of the SMBR maintained high level, and the SMBR system remained stable during this study.

Establishing Submersed Macrophytes via Sinking and Colonization of Shoot Fragments Clipped off Manually

In this paper, sinking and growth of apexes and mid-stems of Myriophyllum spicatum L., Hydrilla verticillata (L.f.) Royle and Ceratophyllum demersum L. in concrete ponds containing eutrophic water and sediment were investigated. Sinking rates of apexes and mid-stems reached 34.8% and 4.4% at the 6 th day and 91.1% and 66.7% at the 22 nd day for M. spicatum, 57.8% and 55.6% at the 6 th day and 100% and 97.8% at the 22 nd day for H. verticillata, 18.9% and 86.7% at the 6 th day and 95.6% and 100% at the 22 nd day for C. demersum, respectively. Most sunken fragments established themselves successfully with significant growth. Total shoot length of plantlets developed from apexes and mid-stems increased by 399% and 61% for M. spicatum, 593% and 256% for H. verticillata and 114% and 104% for C. demersum, respectively. The results showed that it was feasible to establish submersed macrophytes via sinking and colonization of shoot fragments clipped off manually.

Macrophytes in Artificial Wetland

The role and problem of macrophyte in artificial wetland for wastewater treatment are summarized and some research interests are proposed in this paper. Macrophyte plays three important roles in artificial wetland. 1) Uptake the nutrients, adsorb and accumulate heavy metal and poisonous substances from wastewater. 2) Transfer oxygen to rhizophere for the growth, reproduction and decompositions of microorganisms. 3) Enhance and stabilize the hydraulic transportation of media. However, die back of macrophyte, grown weed and shallow extension of root in the wetland, which affect the growth and purification efficiency of plants in wetland, are porblems for artificial wetland management. To strengthen and enhance the roles of macrophyte and the wastewater purification function of artificial wetland, the physiological ecology of macrophyte such as gas transportation and exchange, photosynthesis, stressed physiology and allelopathy of macrophyte should be studied further to select optimum macrophyte species and suitable artificial habitat should be established in the artificial wetland.

Phosphate removal of acid wastewater from high-phosphate hematite pickling process by in-situ self-formed dynamic membrane technology

Phosphate removal from pickling milling wastewater of high-phosphate hematite mineral by in-situ self-formed dynamic membrane reactor (DMR) developed with raw and activated red mud (RM-raw and RM-a) was studied in this paper. The results indicated that RM dosage, velocity gradient of the mixer (G value), reaction time (t), and pH were main effects on phosphate removal. The pH of the actual mineral processing wastewater is 2.50 similar to 2.53 while the phosphate concentration is 98.85 mg/l. After the treatment, the removal rate of phosphorus with RM-raw and RM-a can reach 94.33% and 99.72%, respectively, with the dosage of 23.00 g/l and 20.00 g/l, respectively. Correspondly, effluent pH was respectively 8.12 and 3.06, and both turbidity could reach the effluent requirement. Brush cleaning was a very effective cleaning method, and the membrane flux of DMR could be restored. Also, it demonstrated that acid reuse from the phosphate-contained acidic wastewater from wastewater produced in high-phosphate hematite pickling process could be achieved by in-situ self-formed dynamic membrane technology.

Callus initiation and subculture ofTaxus chinensis

Conditions have been established for the callus initiation and subculture ofT. chinensis. The calli were induced by the explants cultured first on the medium MS supplemented with 1.0 mg/L 2,4-D, 2g/L CH, and 25g/L sucrose, then on The medium: MS+1.0 mg/L NAA+0.5 mg/L BA+2g/L CH+25g/L sucrose. When the callus was subcultured and tamed several times, it could grow fast and stable on the medium: MS+0.2mg/L 2,4-D+0.5 mg/L NAA+0.5 mg/L BA+2g/LCH+25 g/L sucrose. The contamination of explants was a result of endophytic microbes ofT. chinensis. This could be avoided by adopting the tender shoots 3–5 cm long collected in early spring as the source of explants. The browning of the cultures could be prevented and controlled by means of the selection of a suitable explants, hormonal regime in the medium, culture methods and the use of antioxidants.

Phosphorus removal from domestic sewage by adsorption combined photocatalytic reduction with red mud

Phosphorus removal from domestic sewage by adsorption combined photocatalytic reduction with raw and modified red mud (RM) was studied in this paper. The results indicated that RM dosage, reaction time, stirring rate, phosphorus concentration, and initial pH of solution (pH(i)) were the main factors to effect on phosphorus removal. It was found that the phosphorus removal efficiency of modified red mud (RM-m) under the photocatalytic test conditions was higher than only by adsorption process, while raw red mud (RM-raw) showed no significant difference under the two conditions. With initial phosphorus concentration 8.26mg/L, reaction time 60min, stirring rate 200r/min, under the adsorption and photocatalytic test conditions, the optimum dosage and pH(i) of both RM-raw and RM-m were 1.8g/L and 4.0, respectively, and the corresponding phosphorus removal of RM-raw and RM-m were 90.18 and 91.70%, respectively. The optimum amount of RM-m under the two conditions were 1.6 and 1.5g/L, respectively, the optimal pH(i) 3.0, correspondingly, the phosphorus removal could reach high up to 94.30 and 99.96%, respectively.

Dynamics of phytoplankton in the process of the aquatic macrophyte rehabilitation in Lake Yuehu,Wuhan

From December, 2004 to May, 2005 phytoplankton was investigated monthly in the process of the aquatic vegetation rehabilitation in Lake Yuehu, Wuhan. The result indicated that, under the condition of high nutrition concentrations, phytoplankton was still maintained at low biomass and density; phytoplanklon growth was positively correlated with the temperature, but not with nutrient concentrations. Potamogeton cripas and Elodea canadensis made water body maintain higher transparency. Phytoplankton was mainly composed of cryptophyta and diatom. The typical species of water bloom didnt appear with the increase of temperature. The phytoplankton community structure was possibly changed by existence of these two submerged macrophytes. Therefore, rehabilitation of aquatic vegetation was the effective way to control the eutrophication of the lake in winter and spring of lower temperature.

Response between aerenchyma and radial oxygen loss of Acorus calamus Linn. under high nitrogen and phosphorus stress

以湿地植物菖蒲为研究对象,在水培条件下观察3个浓度梯度的氮磷污水(处理组1、2、3依次为N:40 mg/L、P:4 mg/L;N:80 mg/L、P:8 mg/L;N:120 mg/L、P:12 mg/L)对其胁迫后的根系释氧和通气组织的变化规律,研究发现高氮磷胁迫明显抑制菖蒲株高和根系长度的生长,减少植物根系数量;高氮磷胁迫还可以增加植物根系释氧量和促进根系通气组织形成,由于根系长度和数量的减少,处理组的根系释氧总量不及对照组;高氮磷胁迫不改变菖蒲根系释氧趋势,根尖最大,离根尖越远释氧越小.研究还发现,根尖释氧量大小和通气组织呈正相关,根基和根中部释氧量与通气组织关系不显著,说明植物通气组织的形式更有利于根尖释氧.Acorus calamus Linn. has been selected as the experimental plant,and the variation of its aerenchyma and the quantity of its radial oxygen loss ( ROL) under the stress of three different concentrations of nitrogen and phosphorus effluent ( Group 1: N 40 mg /L,P 4 mg /L; Group 2: N 80 mg /L,P 8 mg /L; Group 3: N 120 mg /L,P 12 mg /L) in the water culture has been investigated. The results show that the stress of high concentrations of nitrogen and phosphorus significantly inhibited the growth of root length and plant height of Acorus calamus Linn. and reduced the number of plant roots; it could also increase the quantity of ROL and promote the formation of aerenchyma. The gross quantity of ROL in the stress group was less than that in the control group due to the decrease of root length and quantity. The ROL trend has not changed by the stress of high concentrations of nitrogen and phosphorus,and the further distance away from the roots,the smaller quantity of the ROL. This research also found that the amount of the root tips ROL showed positive correlation with aerenchyma while the amount of ROL of basal zone and mature zone showed insignificant correlation with the aerenchyma.