Department of Limnology and Water Technology

Responses of Anabaena azollae for difierent organic fertilizers; cow dung and banana peel water

Fri, 07 Jun 2024 00:00:00 GMT

Responses of Anabaena azollae for difierent organic fertilizers; cow dung and banana peel water Cottage, K.S.G.; Asanthi, H.B.; Wijewardene, L.N. Organic farming is becoming popular around the globe due to increased public consciousness related to human health risks and environmental impacts associated with using commercial inorganic fertilizers. Nitrogen (N) limitation in organic fertilizers is one of the main constraints which discourage farmers from using them in their fields. Azolla sp. is a floating aquatic fern that contains 4-596 of N content from its dry weight. Furthermore, the presence of symbiont Anabaena azof/ae (cyanobacteria) enhances the N content through the N- fixation. Therefore, Azofla sp. is a potential N source in the production of organic fertilizers. This study aimed to determine the responses of both Azolla sp. and Anabaena azo//ae in liquid cow dung (CD) and banana peel (BP) water and finally to determine the better medium for the growth ofAzof/a sp. The 0.25g of Azo/la sp. was cultured in each water (control) and two treatments such as liquid CD, and BP in a concentration series with triplicates. The CD and BP treatment series were prepared with changing volume ratios such as, 1:0 (TO), 1 :1 (T1), 1:2 (T2), 1:3 (T3), 1:4 (T4) and 1:5 (T5). The biotic parameters ofAzo//a sp. (wet weight, surface area, relative growth rate and total nitrogen content) and Anebaene azollae (heterocyst frequency (HF) and the total number of Anabaena filaments (TF)) were measured at three-day intervals throughout the experiment. Additionally, the water quality parameters (pH, temperature, conductivity, turbidity and salinity) were measured at three-day intervals during the 21 days of the experimental period.The significantly high wet weight (0.314 g),surface area (16.097 cm2) and relative growth rate (0.012 g/g/day) ofAzo//a sp. were recorded at TO in the BP series (p<0.05). Also, the highest total nitrogen content (TN) of Azo/is sp. was recorded as 3.092 mg N/mg in TO of the BP series where only the liquid CD was available in the growth media. The rapid growth ofAzo/fa sp. was observed in that treatment within the first 02 weeks. When considering the measurements of Anabaena azollee, the maximum HF was recorded as 19.35 96 in TO of the BP series while the highest TF was reported as 21 in both T1 in the CD series andT0 in the BP series. A moderately strong correlation (r= 0.3548) was recorded between the HF of Anabaena azollae and the total nitrogen content (TN) of Azo/la sp. Additionally, the RGR ofAzo//ssp. showed a significant positive correlation with both TF and HF of Anabaena azollae under both treatment series. For example, the BP series showed a strong correlation between TF and RGR(r=0.887, p=0.000) (R2 = 78.4696) as welt as between HF and RGR (r = 0.726, p=0.000) (R2 = 52.5596). These correlations indicate the potential use of RGR of the Azolla sp. Which is easy to measure to use in predicting/extrapolating microscopic observations such as HF or TF of Anabaana azollee. Overall, our results suggested that the fertilizer with only cow dung (CD) was the best treatment for increasing the growth and the total nitrogen content ofAzo/la sp. These insights help to develop organic fertilizers using “Azo/la - Ane6aena” the existing Pteridophyte — Blue green algae ecological interaction.

Heterogeneous and homogeneous photocatalytic degradation of chlorophenols in aqueous titanium dioxide and ferrous ion

Sun, 01 Oct 2000 00:00:00 GMT

Heterogeneous and homogeneous photocatalytic degradation of chlorophenols in aqueous titanium dioxide and ferrous ion Doong, R-A.; Maithreepala, R.A.; Chang, S-M. Photocatalytic degradation of 100 mg/l chlorophenols was studied using TiO2 and Fenton reagent as catalysts. 2-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenol were selected as the target compounds. Results showed that direct photolysis of chlorophenols was faster than that in the TiO2-amended system. The photodegradation of 2CP followed a first-order rate relationship and the rate constants were 0.022 and 0.0103 min–1 in direct photolysis and TiO2/UV systems, respectively. The apparent-first-order reaction rate for decomposition of 4-chlorophenol was higher than that for 2-chlorophenol and 2,4-dichlorophenol under acidic conditions, while 2,4-dichlorophenol was higher than 2-chlorophenol and 4-chlorophenol in an alkaline medium. Both the TiO2 catalyst system and direct photolysis process were faster in basic medium than acidic and neutral medium processes. The Fenton system is excellent for the degradation of chlorophenols and its activity has become low in high pH medium.

The influence of pH and cadmium sulfide on the photocatalytic degradation of 2-chlorophenol in titanium dioxide suspensions

Wed, 01 Aug 2001 00:00:00 GMT

The influence of pH and cadmium sulfide on the photocatalytic degradation of 2-chlorophenol in titanium dioxide suspensions Doong, Ruey-an; Chen, Chih-hua The influence of pH and cadmium sulfide on the photocatalytic degradation of 2-chlorophenol (2-CP) in titanium dioxide suspensions was investigated to evaluate the feasibility of mixed semiconductors on the photodegradation of chlorinated organics in aqueous solution. Apparent first-order rate constants (kobs) and initial rate constants were used to evaluate the degradation efficiency of 2- CP. Higher degradation efficiency of 2-CP was observed at higher pH values. The apparent pseudo-first-order rate constant was 0.036 min-1 at pH 12.5 in TiO2/UV system, while a 2- to 9-fold decrease in kobs was observed over the pH range of 2.5–9.5. The addition of phosphate buffer solutions at different pH values have different effects on the degradation of 2-CP. H2PO- 4 has little effect on the photodegradation of 2-CP, while HPO2- 4 could inhibit the photodegradation efficiency of 2-CP. Chlorocatechol, hydroquinone, benzoquinone and phenol were identified as the predominant aromatic intermediates for the photocatalytic degradation of 2-CP. Moreover, less aromatic intermediates at higher pH were observed. Direct oxidation contributed significantly to the photodegradation of 2-CP. An addition of a semiconductor decreased the initial and apparent first-order rate constants of 2-CP. The cutoff of wavelength of 320 nm could diminish the contribution of direct photolysis of 2-CP. The combination of cadmium sulfide and titanium dioxide can lead to an enhanced rate of disappearance of 2-CP compared to those in single semiconductor system. A 1.2 to 2.5-fold increase in rate constant in coupled semiconductor system relative to the single semiconductor system was obtained. © 2001 Elsevier Science Ltd. All rights reserved

Enhanced remediation of carbon tetrachloride by Fe(II)-Fe(III) systems in the presence of copper ions

Thu, 01 Jan 2004 00:00:00 GMT

Enhanced remediation of carbon tetrachloride by Fe(II)-Fe(III) systems in the presence of copper ions Maithreepala, R.A.; Doong, R-A. The effect of Cu(II) ion on the dechlorination of carbon tetrachloride (CT) by Fe(II) associated with various iron oxides was investigated. Iron oxides including goethite, hematite, ferrihydrite and magnetite were selected as the model compounds. CT was dechlorinated to chloroform (CF) by 3 mM Fe(II) in iron oxide suspensions at pH 7.2. The dechlorination followed pseudo first-order kinetics and the pseudo first order rate constants (kobs) were 0.048 h–1, 0.0836 h–1, 0.0609 h–1 and 0.0144 h–1 in goethite-, hematite-, ferrihydrite- and magnetite-amended systems, respectively. Addition of Cu(II) into systems increased the kobs for CT dechlorination significantly. A 3- to 120-fold increase in kobs relative to the systems without Cu(II) was observed when 0.5 mM Cu(II) was added to the Fe(II)-Fe(III) suspensions. The pH of the system is an important factor controlling the dechlorination rate of CT. The increase in concentrations of Fe(II) and iron oxides also enhanced the dechlorination efficiency and rate of CT. Moreover, a linear relationship between the kobs and Cu(II) concentration ranging between 0 and 0.4 mM was observed. Results obtained demonstrate the feasibility of using surface-bound iron species with Cu(II) for the detoxification of chlorinated solvents in the contaminated aquifers.