Treatment of high-strength wastewater in tropical vertical flow constructed wetlands planted with Typha angustifolia and Cyperus involucratus

The ability of vertical flow (VF) constructed wetland systems to treat high-strength (ca. 300 mg L^?1 of COD and ca. 300 mg L^?1 total-nitrogen) wastewater under tropical climatic conditions was studied during a 5-month period. Nine 0.8-m diameter experimental VF units (depth 0.6 m) were used: three units were planted with Typha angustifolia L., another three units were planted with Cyperus involucratus Rottb and three units were unplanted. Each set of units were operated at hydraulic loading rates (HLRs) of 20, 50 and 80 mm d^?1. Cyperus produced more shoots and biomass than the Typha, which was probably stressed because of lack of water. The high evapotranspirative water loss from the Cyperus systems resulted in higher effluent concentrations of COD and total-P, but the mass removal of COD did not differ significantly between planted and unplanted systems. Average mass removal rates of COD, TKN and total-P at a HLR of 80 mm d^?1 were 17.8, 15.4 and 0.69 g m^?2 d^?1. The first-order removal rate constants at a HLR of 80 mm d^?1 for COD, TKN and total-P were 49.8, 30.1 and 13.5 m year^?1, respectively, which is in the higher range of k-values reported in the literature. The oxygen transfer rates were ca. 80 g m^?2 d^?1 in the planted systems as opposed to ca. 60 g m^?2 d^?1 in the unplanted systems. The number of Nitrosomonas was two to three orders of magnitude higher in the planted systems compared to the unplanted systems. Planted systems thus had significantly higher removal rates of nitrogen and phosphorus, higher oxygen transfer rates, and higher quantities of ammonia-oxidizing bacteria. None of the systems did, however, fully nitrify the wastewater, even at low loading rates. The vertical filters did not provide sufficient contact time between the wastewater and the biofilm on the gravel medium of the filters probably because of the shallow bed depth (0.6 m) and the coarse texture of the gravel. It is concluded that vertical flow constructed wetland systems have a high capacity to treat high-strength wastewater in tropical climates. The gravel and sand matrix of the vertical filter must, however, be designed in a way so that the pulse-loaded wastewater can pass through the filter medium at a speed that will allow the water to drain before the next dose arrives whilst at the same time holding the water back long enough to allow sufficient contact with the biofilm on the filter medium.     

Characteristics of Sulfite Transport by Chlorella vulgaris

The rate of short-term accumulation of [³⁵S]sulfite in Chlorellavulgaris cells was found to be strongly dependent on the pHof the medium. The rate increased with decreased pH, and theincrease in rate closely paralleled the increase in the concentrationof the un-ionized form of sulfite. When the pH of the mediumwas increased, fast accumulation ceased immediately. The rateof accumulation showed a strong temperature dependence, withan apparent temperature coefficient of 1.93 per 10°C rise,between 10 and 25°C. Because pK_a values of sulfite shiftwith temperature, the rates were corrected by dividing by theconcentration of the un-ionized form of sulfite present at therespective temperatures. The temperature coefficient was thenfound to decrease to 1.45. When cells which had been allowedto accumulate [³⁵S]sulfite for 20 min were transferred to amedium containing no sulfite, more than 50% of the accumulated[³⁵S] was released into the medium in 20 min. Our results arecompatible with a simple diffusion model of SO₂ transport intoChlorella cells. (Received September 26, 1996; Accepted January 20, 1997)     

Acetylcholinesterase-inhibiting steroidal alkaloid from the sponge Corticium sp

A new stigmastane-type steroidal alkaloid, 4-acetoxy-plakinamine B (1), was isolated from the Thai sponge Corticium sp. The compound was subjected to the acetylcholinesterase inhibitory activity determination to reveal a high inhibitory activity (IC(50) 3.75+/-1.69 microM). The kinetics of enzyme inhibition showed a decrease in V(max), whereas K(m) was increased, thus suggesting an unusual mixed-competitive mode of inhibition. Compound 1 is the first steroidal alkaloid bearing a stigmastane skeleton ever been reported to exhibit such good potency in the acetylcholinesterase inhibition bioassay.     

Intracolonial allocation of trisoxazole macrolides in the sponge Pachastrissa nux

Pachastrissa nux has two distinctive growth forms in one colony, i.e., the protruding gorgonian-shaped capitum and the substratum-attached irregular-shaped base. The sponge has the ability to allocate specifically its major secondary metabolites to the two parts in different levels. Using two cytotoxic trisoxazole macrolides, kabiramides C (2) and G (3), as chemical markers, it was found that the capitum accumulated higher contents of either or both compounds than did the base. However, there were neither inductive nor suppressive correlations among the allocation profiles of either compound in either part of the sponge. The allocation of kabiramides was a trade-off with the structural materials involved in reinforcing the strength of the sponge. To date, this is the second report that provides evidence of the specific allocation of bioactive metabolites in two distinctively different organ-like structures in a single sponge colony.