Use of autoclaved aerated concrete particles for simultaneous removal of nitrogen and phosphorus as filter media from domestic wastewater.

ABSTRACT In this study, autoclaved aerated concrete particles (AACPs) from construction waste were used to simultaneously remove phosphorus and nitrogen in biological aerated filters (BAFs). The effects of air/water (A/W) ratio on the removal performance of phosphorus (PO4 3-), total organic carbon, total nitrogen (TN), and ammonia nitrogen were investigated. Results showed that AACP BAF was more efficient than commercially available ceramsite (CAC) BAF. For example, the removal rates of TN with AACP and CAC were 45.96% and 15.64%, respectively, and those of PO4 3- with AACP and CAC were 72.45% and 33.97%, respectively, at the A/W ratio of 3:1. Different characterization methods were utilized to evaluate the surface shape, elemental compostion, and internal and surface structure of AACP. The interconnectivity and uniformity of pores and the rough surface of AACP were found to be suitable for the growth of microbial biofilm. In addition, the growth of internal pores in AACP promoted the removal of phosphorus and nitrogen. The surface of used AACP contained a small amount of irregular crystals and was covered with a layer of aggregates, which were characterized as hydroxyapatite [HAP, Ca5(OH)(PO4)3]. The formation of HAP as a final byproduct confirmed the successful removal of phosphorus. Therefore, construction wastes, such as AACPs, could be recycled and utilized as a promising biofilter media for excellent wastewater treatment.

[Effects of different phosphorus substrates on the growth and phosphatase activity of Skeletonema costatum and Prorocentrum donghaiense].

The effects NaH2PO4, adenosine disodium triphosphate (ATP), glucose 6-phosphate (G-6-P) and sodium beta-glycerophosphate (G-P) on the growth and phosphatase activity of Skeletonema costatum and Prorocentrum donghaiense were studied. The results showed that both species could utilize both dissolved inorganic phosphate (DIP) and dissolved organic phosphorus (DOP), and DOP had more effects on the growth of two species than DIP. For S. costatum, after 8 days, the cell abundances of the four treatments (NaH2PO4, ATP, G-6-P and G-P) were 48 x 10(4), 73 x 10(4), 63 x 10(4) and 54 x 10(4) cells/mL, respectively; For P. donghaiense, after 10 days, the cell abundances of the four treatments were 8.7 x 10(4), 15.5 x 10(4), 12.4 x 10(4) and 9.5 x 10(4) cells/mL, respectively. On the first 3-4 days, the phosphatase activity of all treatments of the two species showed a decreasing trend, but different changes were observed for the different phosphorus substrate treatments in latter days. For the NaH2PO4 treatment, both the AP and AcP activity of two species increased from the fifth day onwards. For S. costatum, the AP activity of the ATP and G-6-P treatment groups showed no obvious changes and AcP activity had a slight increase from the fifth day to the eighth day, while the activity of G-P treatment had highest phosphatase activity which increased from the fifth day on. At the end of the experiment, the AP activity of the three DOP treatment groups (ATP, G-6-P and G-P) was 0.004 x 10(-5), 0.014 x 10(-5) and 0.029 x 10(-5) U/cell, respectively, and the AcP activity was 0.006 x 10(-5), 0.011 x 10(-5) and 0.018 x 10(-5) U/cell, respectively. For P. donghaiense, both the AP and AcP activity of the three DOP treatments had similar trends, i.e., ATP < G-6-P < G-P. Under the same nutrient conditions, S. costatum had a much higher phosphatase activity and could absorb P from the environment much faster than P. donghaiense.

[Comparative research on the effects of different nutrient concentrations on the photopigment content and photosynthesis of two bloom-forming species isolated from the Changjiang River estuary].

The contents of cellular chlorophyll a (Chl-a), chlorophyll c (Chl-c), total coloured carotenoids (TCC) and the photosynthesis of Skeletonema costatum and Prorocentrum donghaiense under different nutrient conditions were studied. The results showed that both species in the low nutrient concentration conditions had lower cellular Chl-a, Chl-c and TCC content than those in the high nutrient concentration conditions. When the initial N/P ratio was 16/1 while the concentrations were different, the two species had different photosynthetic rate responses. For S. costatum, the photosynthetic rate normalized by cell in the low nutrient concentration group (64 micromol/L N and 4 micromol/L P) was significantly lower than that in the high concentration group (256 micromol/L N and 16 micromol/L P) from the fifth day, and at the end of the experiment (on the seventh day), the photosynthetic rate was 0.031 x 10(-4) micromol x (cell x h)(-1) and 0.13 x 10(-4) micromol x (cell x h)(-1) respectively, while the photosynthetic rate normalized by Chl-a was 12.92 micromol x (microg x h)(-1) and 13.03 micromol x (microg x h)(-1) for the two groups respectively, and there was no significant difference between them; however, for P. donghaiense, the photosynthetic rates normalized by both cell and Chl-a in the low concentration conditions (64 micromol/L N and 4 micromol/L P) were significantly higher than those in the high concentration conditions (256 micromol/L N and 16 micromol/L P). For the two species, when P was sufficient, the low N concentration group (64 micromol/L N and 36 micromol/L P) and when N was sufficient, the low P concentration group (883 micromol/L N and 4 micromol/L P) had higher photosynthetic rates normalized by both cell and Chl-a than the high N concentration group (256 micromol/L N and 36 micromol/L P) and the high P concentration group (883 micromol/L N and 16 micromol/L P) respectively. There was a significant positive relationship between the photosynthetic rate and the intracellular P for both species, and P. donghaiense had higher cellular photopigment contents and photosynthetic rates than S. costatum under the same nutrient conditions. It could be inferred from their photosynthetic characteristics that P. donghaiense would survive better in low nutrient conditions compared with S. costatum.