Haiyan Pei

Effect of protease and cellulase on the characteristic of activated sludge.

Sludge dewatering is a key part of sludge disposal since it can greatly reduce the volume of sludge and thus improve the treatment effect for handling and disposing. This study investigated the potential benefits of enzymatic pretreatment on activated sludge dewatering with protease and cellulase as a protein and polysaccharide degrading enzyme, respectively. Capillary suction time (CST) and the solid content after centrifugation were used to evaluate sludge dewatering. The particle size distribution, extracellular polymeric substances (EPS) content, infra-red (IR) spectrometry and microscope image were determined in an attempt to explain the observed changes in sludge dewaterability. The results indicated that adding protease and cellulase separately leads to an increase in CST and the increased value is higher with protease. Protease and cellulase both promote the degradation of protein and polysaccharide in the solids of activated sludge, leading to a smaller particle diameter and poorer dewaterability. However, due to the limited effects on the protein and polysaccharide content, the difference in sludge dewaterability is not large. Compared to the control, enzymatic pretreatment had no obvious effect on sludge IR spectrometry, while there was a detectable structure difference at a colloidal scale.

Detection of amount and activity of living algae in fresh water by dehydrogenase activity (DHA)

A study was performed to determine the amount and activity of living algae in fresh water by measuring the dehydrogenase activity (DHA) of algae in order to provide a method to assess the effect of algicide treatment. The conditions of measurement were researched with respect to incubating temperature and duration, and selection of extractants. The comparison between this method and an alternative method, chlorophyll a, shows that this method is simple and easy to practice, and can determine the effect of algicide treatment.

Assessment of Trophic Status for Nansi Lake Using Trophic State Index and Phytoplankton Community

The present study was to investigate the trophic state of Nansi Lake, a shallow lake employed in the South-to-North Water Diversion Project in China. Based on water transparency, total phosphorus (TP) and chlorophyll a (chl a) concentration, the modified method of Carlsons trophic state index (TSIM) was applied to assess the lakes trophic status. The Shannon diversity index of phytoplankton was calculated. According to the majority of the investigated parameters and indices derived from phytoplankton, Nansi Lake is eutrophic.

The Effect of Mechanical Agitation on the Stripping of Bio-Film from Ceramic Particles

The effects of mechanical agitation on the stripping of attached-growth bio-film from ceramic particles were studied under the conditions of different agitating speeds and durations. The results indicated that the stripping efficiency of bio-film was increased with the increase of agitating speed. The highest stripping efficiencies at the low, middle and high speeds of 300, 600 and 1200 rpm/min were 16.8, 27.4 and 48.8% respectively. The increase of agitating duration can increase the stripping efficiency of bio-film. However, as the duration exceeded 90 minutes, the increase of stripping efficiency for three speeds shows no obvious change. The variation of mass fraction of small floc and the productivity of polysaccharide and protein in suspension revealed that mechanical agitation also gave rise to the release of extra-polymer substance and the disaggregation of the stripped bio-film at the time of improving the stripping efficiency of bio-film.

The Dispersion of Extra-Polysaccharide and Protein of Activated Sludge in Sodium Pyrophosphate Solution

The dispersion of extra-polysaccharide and protein of sludge in sodium pyrophosphate solution (pH=7.0) was studied under the conditions of low mixing speed. The results showed that as the mixing speed were set at 150 and 350 rpm/min, the dispersion of polysaccharide and protein in sodium pyrophosphate solution was mainly controlled by chemical process, and the dispersion efficiency of protein was greater than polysaccharide. It was analyzed that the different affinity of protein and polysaccharide to bivalent Ca2+ was the main factor resulting in their different dispersion characteristic in sodium pyrophosphate solution.

Nitrification Performance of a Pilot-Scale UBAF Treating Secondary Effluent of Municipal Sewage

A pilot-scale of up-flow biological aerated filter (UBAF) treating secondary effluent of municipal sewage was constructed and operated for 189 days from April 12th to October 18th. The nitrification performance of UBAF under two different air flow rates (0.6 and 1.0 m 3 /h) was studied. The Run I (air flow rate=0.6 m 3 /h) and Run II (air flow rate=1.0 m 3 /h) worked for 90 and 99 days respectively. During the whole operating process, the influent ammonium concentration varied within the range of 9.27-22.3 mg/L and the inflow hydraulic load was kept at 15.92 m 3 /m 3 substratum ldrd. The water temperature was 16.9-26.2degC. Air and water backwashing was conducted once per 48 h and lasted 15 min. The corresponding backwash superficial velocities were set as 50 and 15 m/h. The experiment results showed that the average ammonium removal efficiency were 64.5% in Run I and 90% in Run II. About 95% removal ammonium was converted to nitrate in the two Runs. As the air flow rate was 0.6 m 3 /h, the nitrite accumulation phenomenon occurred in the bottom but it was undetectable in the final effluent. In Run II, the nitrite accumulation phenomenon could not be detected thoroughly in the reactor.

Study on the Method of Detecting Dehydrogenase Activity of Living Algae in Fresh Water

The method of detecting dehydrogenase activity (DHA) of algae in fresh water was studied. The determining conditions were researched with respect to TTC concentration, incubating temperature and duration, and selection of extractants. Compared with the method of chlorophyll a, it performed a better precision, and was easy and simple to practice.