Zhenqiang Fan

Effect of filter-feeding fish silver carp on phytoplankton species and size distribution in surface water: A field study in water works

Silver carp were introduced into the pre-sedimentation pond to control excessive phytoplankton in raw water. The effectiveness of the filter-feeding silver carp on phytoplankton control and the effect of silver carp on phytoplankton community were investigated. The results showed that Microcystis could be effectively removed by silver carp stocked in the pre-sedimentation pond, and simultaneously, the concentration of single-cell phytoplankton increased obviously. The difference in phytoplankton species and single-cell phytoplankton size between in the water and in the gut of silver carp indicated that phytoplankton smaller than 5 microm, such as Chamydomonas and Platymonas, were almost not be filtered by silver carp, phytoplankton with the size between 5 and 20 Csm could be partly filtered, and large size phytoplankton, mainly colony-forming Microcystis could be filtered almost completely. These filter-feeding characteristics directly caused the phytoplankton size distribution biased toward miniaturization. Therefore, this biological treatment using silver carp could be applied only to deal with groups of Microcystis-dominated eutrophic water, and was not appropriate in water bodies where single-cell micro phytoplankton were dominant. Especially when silver carp are used in water treatment, a cautious attitude should be taken based on the evaluation of phytoplankton biomass and species structure features in raw water.

Pilot study on control of phytoplankton by zooplankton coupling with filter-feeding fish in surface water.

A pilot-scale facility was originally designed to control phytoplankton in algae-laden reservoir water characterized by summer cyanobacteria blooms (mainly Microcystis flos-aquae). The system made good use of the different food habits of Daphnia magna and silver carp. Zooplankton (Daphnia magna), filter-feeding fish (silver carp), and zooplankton (Daphnia magna) were stocked in three separated tanks in sequence, respectively. Thus, single-cell phytoplankton and some Microcystis flos-aquae in small size were first grazed by Daphnia magna in the first tank, and in the second tank phytoplankton larger than 10 microm were filtered by silver carp, and the concentration of the remaining phytoplankton was further reduced to a rather low level by Daphnia magna in the third tank. The results showed that the system had good removal efficiencies of phytoplankton and chlorophyll a, 86.85% and 59.41%, respectively, and permanganate consumption (COD(Mn)) and turbidity were lowered as well. A high phytoplankton removal efficiency and low cost indicated that the system had a good advantage in pre-treating algae-laden source water in drinking water works.

Bio-reaction of nitrobenzene with Microcystis aeruginosa: characteristics, kinetics and application.

The bio-reaction of nitrobenzene (NB) with Microcystis aeruginosa was investigated at different initial algal densities and NB concentrations by performing static experiments. The results showed that the elimination of NB was enhanced by the bio-reaction, and the reaction rate varied as a function of the reaction time. Moreover, the reaction rate was significantly affected by the algal density and NB concentration. A kinetic analysis showed that the elimination of NB in a solution without algae appeared to be pseudo-first-order with respect to the NB concentration, whereas a first-order model was too oversimplified to describe the elimination of NB in a solution with algae. Assuming that different algal cells have the same effect on the bio-reaction under the same conditions, the bio-reaction can be described as dC(NB) = -k(0)C(A)(m)A(NB)(n)dt (where k(0) is the reaction rate constant, C(A) is the algae density and C(NB) is the concentration of NB). When the growth of algae was not considered, the value of k(0), m and n were 8.170 × 10(-4), 0.5887 and 1.692, respectively. Alternatively, when algae were in the exponential growth phase, the value of k(0), m and n were 1.6871 × 10(-5), 0.7248 and 2.5407, respectively, according to a nonlinear fitting analysis. The kinetic model was also used to elucidate the effect of nutritional limitation on the bio-reaction.

The transformation mechanism of nitrobenzene in the present of a species of cyanobacteria Microcystis aeruginosa

The transformation mechanism of nitrobenzene (NB) with Microcystis aeruginosa was investigated by a series of laboratory-scale experiments. The result showed only a small fraction of NB can be adsorbed by M. aeruginosa. The adsorption was responsible to the transformation of NB in M. aeruginosa solution but was not the primary cause. The variation of cell activity and illumination could affect the transformation of NB with M. aeruginosa, which indicated that M. aeruginosa have the ability to biodegrade NB. Metabolic intermediate products analysis indicated that M. aeruginosa can reduce NB to aniline (AN), and NB reductase, induced by NB, was the key enzyme during the reduction process. M. aeruginosa cannot further degrade AN and may prevent the volatilization of AN, causing the accumulation of AN in the solution for up to 3 days. Only a small proportion of AN (less than 5%) can be degraded to acetaldehyde and acetone by photolysis in 48 h. The total concentration of nitrogen aromatic compounds is invariant at first, and then decreases after 72 h incubation via a complex process including adsorption, biodegradation, volatilization and photolysis processes.

The interaction between nitrobenzene and Microcystis aeruginosa and its potential to impact water quality

The potential water quality problems caused by the interaction between nitrobezene (NB) and Microcystis aeruginosa was investigated by studying the growth inhibition, the haloacetic acids formation potential (HAAFP) and the secretion of microcystin-LR (MC-LR). The results showed that NB can inhibit the growth of M. aeruginosa, and the value of EC50 increased with the increase of initial algal density. Although NB can hardly react with chlorine to form HAAs, the presence of NB can enhance the HAAFP productivity. The secretion of the intracellular MC-LR is constant under the steady experimental conditions. However, the presence of NB can reduce the MC-LR productivity of M. aeruginosa. Overall, the increased disinfection risk caused by the interaction has more important effect on the safety of drinking water quality than the benefit of the decreased MC-LR productivity, and should be serious considered when the water contained NB and M. aeruginosa is used as drinking water source.

Reproduction of Staurastrum sp. within a water treatment plant caused by the recycle of combined sludge water and backwash water: a field investigation

AbstractIt is well known that the recycle of sludge water and filter backwash water in drinking water treatment plants (WTP) may cause water quality problems including suspended solids, pathogenic protozoans, dissolved organic matters, and disinfection by-products. However, it is still uncertain whether the recycle process can cause algal problems in a WTP with algal-laden raw water. A field survey was performed in a WTP, located in Tianjin, China, to investigate the variation of algal species and density during the treatment and recycle process. The results showed Staurastrum sp., a non-dominant species in raw water, regrew and became the unique dominant species in the combined sludge tank (CST). The reproduction of Staurastrum sp. increased the treatment loading, clogged the filter, and deteriorated the quality of finished water. Bench-scale experiments indicated chlorination was inefficient to inactive Staurastrum sp., which resulted in that living cells of this alga can enter into the CST. Culture exp...