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A new process using a sequencing batch reactor (SBR) and two smaller sludge hoppers is proposed for the simultaneous removal of phosphorus and nitrogen from wastewater. In the double sludge switching sequencing batch reactor, denitrifying phosphate accumulating bacteria (DPB) sludge and nitrification sludge are transferred to the SBR at different phases instead of flowing wastewater through different reactors. The process was operated with a cycle time of 10.5 h, consisting of DPB sludge filling phase (0.5 h), anaerobic phase I (2.0 h), settling and changing DPB sludge phase (0.5 h), anaerobic phase II (0.5 h), aerobic phase (4.0 h), settling and changing nitrifying sludge phase (0.5 h), and anoxic phase (3.0 h). Results of stable operation showed that the process was very efficient over a range of temperatures varied from 10 to 28[degrees]C. The average effluent concentrations and removal efficiencies were as follows: CO[D.sub.Cr] 28.0 mg/L, 92.1%; BO[D.sub.5] 7.0 mg/L, 95.1%; N[H.sub.3]-N 0.8 mg/L, 98.0%; TN 9.8 mg/L, 76.7%; and TP 0.5 mg/L, 92.3%. DOI: 10.1061/(ASCE)0733-9372(2008)134:11(923) CE Database subject headings: Simulation; Nitrogen; Phosphorus; Sludge; Reactors.

A pronounced dominance of toxic cyanobacteria has been found in eutrophic water bodies, with Microcystis being a common species. Although toxic cyanobacteria are commonly described worldwide, few recent papers on the sensitive and effective quantification of cyanobacteria have been published. In this paper, a multi-technique approach was applied by the use of cell density counting, cell viability testing, chlorophyll a determination, microcystin monitoring and gene extraction techniques to quantitatively analyse the cyanobacterial biomass of Microcystis aeruginosa FACHB-905. The entire dataset was used to examine the relationships between these indices. Results showed that, for 107 viable cells in the experimental conditions, the contents of chlorophyll a, microcystin-LR and total genes (16S rDNA) averaged 2.65 μg, 0.61 μg and 0.79 μg, respectively. For different cell viability proportions in the same particular phase of growth, it is easy to obtain the respective amount of viable cells and inactive cells and their measurable indices when any one of the three indices, chlorophyll a, DNA or microcystin-LR, is measured. This study provides a new perspective and method for determining multiple indices of toxic cyanobacteria during the same conditions and phases. [ABSTRACT FROM PUBLISHER]

Abstract: The membrane integrity of cells is significant for the safe and effective removal of cyanobacterial cells from drinking water sources. In this paper, cell density counting, cell viability testing, chlorophyll-a determination, extracellular MC-LR monitoring and PCR–DGGE analysis were applied to assess the effects of coagulant dose, shear and floc storage time on the integrity of Microcystis aeruginosa FACHB-905. Results showed that all cells were removed without damage to membrane integrity under the optimum coagulation conditions: coagulant dose 15mg/L AlCl3, rapid mix speed 250r/min, rapid mix time 1min, slow mix speed 20r/min, slow mix time 20min. The coagulant dose and shear did not cause the lysis of cells and ensuing release of MC-LR. But when the flocs were stacked over 6days, the cells lysed and the MC-LR concentration increased above the background level. In addition, the degree of cell breakage without coagulation was higher than the coagulated cells in flocs. Therefore, keeping the flocs safely treated or disposed of on time as well as keeping the cyanobacterial cells integrally removed plays an important part in controlling the harm of blooms to drinking water production. [Copyright &y& Elsevier]

The degradation kinetics of strains P05 and P07 and the degradation effects of mixed strain on Microcystis aeruginosa were studied. The results showed that: (1) The degradation processes of strains P05 and P07 on Microcystis aeruginosa accorded with the first-order reaction model when the range of Chl-a concentration was from 0 to 1500 μg/L. (2) The initial bacterium densities had a strong influence on the degradation velocity. The greater the initial bacterium density was, the faster the degradation was. The degradation velocity constants of P05 were 0.1913, 0.2175 and 0.3092 respectively, when bacterium densities were 4.8 × 10^5, 4.8 × 10^6, 2.4 × 10^7 cells/ml. For strain P07, they were 0.1509, 0.1647 and 0.2708. The degradation velocity constant of strain P05 was higher than that of P07 when the bacterium density was under 4.8 × 10^5 cells/ml, but the constant increasing of P07 was quicker than that of P05. (3) The degradation effects of P05 and P07 strains did not antagonize. When the concentration of Chl-a was high, the degradation effects of mixed strain excelled that of any single strains. But with the decrease of the Chl-a concentration, this advantage was not clear. When the concentration was less than 180 μg/L, the degradation effects of mixed were consistent with that of strain P07. [ABSTRACT FROM AUTHOR]

To investigate the distribution characteristics of the cyanobacteria community and the driving factors in impounded lakes and reservoirs in Shandong on the east route of the South-to-North Water Diversion Project, monthly samples of phytoplankton and the aquatic environment from Nansi Lake, Dongping Lake, Datun Reservoir, Donghu Reservoir, and Shuangwangcheng Reservoir were collected from May to November during 2010 to 2019. A total of 44 planktonic cyanobacteria taxa were identified with 23 filamentous cyanobacteria taxa. Pseudanabaena limnetica, Cylindrospermopsis raciborskii, Microcystis aeruginosa , and Microcystis wesenbergii were the dominant harmful cyanobacteria species, with a high detection frequency and abundance in all lakes and reservoirs. By analyzing the distribution characteristics of the cyanobacteria community in impounded lakes and reservoirs, we found that filamentous cyanobacteria had growth advantages in the water with large hydraulic disturbances, which should be the key points of cyanobacteria prevention and control in the future. Pearson correlation analysis and generalized linear fitting curve results showed that total nitrogen, total phosphorus, water temperature, and water depth played a key role in affecting the growth of P. limnetica, C. raciborskii, M. aeruginosa , and M. wesenbergii . The nitrogen and phosphorus nutrients could promote the growth of harmful cyanobacteria. Due to the good temperature adaptability, P. limnetica could still become the dominant species in early summer and late autumn, and C. raciborskii, M. aeruginosa , and M. wesenbergii had growth advantages when the water temperature was higher than 25℃. In addition, shallow water was more conducive to the growth of C. raciborskii . It was suggested that based on strengthening of the control of nitrogen and phosphorus nutrient input in lakes and reservoirs, the key monitoring of P. limnetica in lakes should be conducted in early summer and late autumn, and the growth of C. raciborskii in shallow water areas should be paid close attention in the high temperature period to ensure the safety of water quality.

The effects of 2-aminophenol and 3,3',4',5-tetrachlorosalicylanilide on biomass yields were studied. The results shows that when AP is 15 mg/L and TCS is 1.2 mg/L, observed growth yields (Yobs) of the sludge are reduced by 21% and 52% with low reduction of COD removal efficiency. Removal rates of ammonia decrease by 32% with TCS but are not affected obviously by AP. The effects of AP and TCS on dewater ability and settle ability of sludge were also investigated. The dewater ability of sludge is not affected by the two uncouplers. The SVI values of sludge with TCS increase slightly. According to microscope observation, the sludge microbe population changes. Meanwhile quantities and kinds of protozoan and metazoan were reduced.

The dewaterability and particle size distribution of activated and digestion sludge were studied. Meanwhile, the related mechanism was explored through analyzing the extracellular polymeric substances (EPS) content and microbe characteristic of activated and digestion sludge. The dewaterability was evaluated using the capillary suction time (CST) and settling property. The CST of activated sludge and digestion sludge are 9.84 s and 607.5 s, respectively. The settling time of the solids of digestion sludge is longer than that of activated sludge. The major reason of poor dewaterability of digestion sludge is the degradation of carbohydrate and protein parts of EPS. In addition, the quantity of protozoan in digestion sludge is less than that of activated sludge, resulting in reducing the excretion of certain matters benefiting the agglomeration between microbes. The EPS content of digestion sludge is 123 mg/g, which was 77% less than that of activated sludge. The degradation of EPS during the digestion process leads to the smaller particle size of digested sludge, and then the poorer dewaterability. The particle size that occupied maximum volume in activated sludge is 133 microm, while it is 44.6 microm in digestion sludge. The mean particle size of activated sludge is 132.6 microm which is larger than that of digestion sludge (70.48 microm).