Characterization of Treatment Processes and Mechanisms of COD, Phosphorus and Nitrogen Removal in a Multi-Soil-Layering System

Characteristics of the treatment processes inside a MSL system were investigated by using a laboratory-scale MSL system, which was set up in a D 10 × W 50 × H 73 cm acrylic box enclosing "soil mixture blocks" alternating with permeable zeolite layers. For the study of the treatment processes inside the system, wastewater, with mean concentrations (mg L⁻¹) of COD: 70, T-N: 12, T-P: 0.9, was introduced into the system at a loading rate of 1,000 L m⁻² d⁻¹. Treatment processes in the MSL system were different for the COD, P and N pollutants. Eighty percent of COD was removed in the 1st soil layer among the 6 layers, and the removal rate increased as water moved down and finally reached 90% in the last layer of the system. Phosphorus concentration was lower under the soil mixture layers than under the permeable layers, presumably because P was adsorbed mainly by soil and mixed iron particles. The P concentration in water gradually decreased in the lower layers of the system. The concentration of PO₄^3--P was generally lower in the aerated MSL system than in the non-aerated one. NH₄⁺-N was adsorbed and nitrified in the upper part of the system. The NO₃⁻-N concentration was lower in water under the soil mixture layers than under the permeable layers, indicating that denitrification mainly occurred in the soil mixture layers.     

Observation of three‐dimensional flow structures and effluent transport around fish cages using a towed ADCP and free‐fall multi‐parameter profiler

A field campaign was conducted around salmon cages, using a combination of a towed ADCP and a free‐fall multi‐parameter profiler, in order to investigate flow structures and the possible distribution of effluent materials. Two transect observations showed that hydrographic conditions changed dramatically within 5 days, from highly stratified open water conditions to weak stratification. Three‐dimensional observation revealed that flow was blocked behind the cages and that the blockage was reduced as the distance from the cages increased. The flow speed was positively correlated with the intensity of the backscattering signal. The R² value was high immediately behind the cages and decreased with distance from the cages. The flow time series behind the cages exhibited a k^–2 power law spectrum that was consistent with a typical internal wave spectrum. This suggests that eddies shed from the cages were highly influenced by stratification. We estimated the rate of kinetic energy dissipation, , from YODA Profiler data based on the Thorpe scale approach. We also estimated the eddy diffusivity coefficient, . Both and followed a lognormal probability density function. The mean was consistent with a one‐dimensional diffusion model assessed from the R² values of flow speed and backscatter intensity.     

Mineral composition of leaves and bark in aluminum accumulators in a tropical rain forest in Indonesia

Mineral composition including AI, Ca, Mg, P, S, and Si and relationships between Al and other elements such as Ca, Mg, P, S, and Si in leaves and bark of trees in a tropical rain forest in West Sumatra were studied. Sixty five tree species and 12 unidentified trees were referred to as AI accumulators based on Chenery\s's definition (more than 1 g kg^-1 Al in leaves). For most of the Al accumulators, Al concentration in leaves was higher than in bark. However, some members of Euphorbiaceae, Melastomataceae, and Ulmaceae families showed a reverse trend. Most of the non-accumulators also showed a higher Al concentration in bark than in leaves. These results indicated that there was a difference in the mechanism of Al accumulation in tree bodies. Some of the Al accumulators showed an extremely high Al concentration (more than 10 g kg^-1) not only in the mature leaves, but also in the new leaves. Analysis of the relationships between the concentration of Al and the other 5 elements in leaves, revealed that Al accumulators could be separated into two groups at the Al concentration of 3 g kg^-1. This finding suggested that new criteria based on Al concentration (23 g kg^-1) or Al/Ca ratio in leaves could be proposed in order to define Al accumulators, apart from Chenery's criterion. Aluminium accumulators with an Al concentration in leaves lower than 3 g kg^-1 (AI accumulators <3 g kg^-1) showed the same trend as the non-accumulators in terms of these elemental relationships, while Al accumulators with an Al concentration in leaves higher than 3 g kg^-1 (AI accumulators 23 g kg^-1) showed a different trend from the non-accumulators. The Al accumulators 23 g kg^-1 and the other trees (AI accumulators < 3 g kg^-1 and non-accumulators) showed separately positive correlations between the concentrations of AI and Ca (or Mg) in the leaves. This observation seems to be opposite to general findings in plant nutrition, i.e. inhibition of Ca or Mg uptake by AI. A positive correlation between Al and S was also observed for all the trees. The Al accumulators ≥3 g kg^-1 showed positive correlations between the concentrations of Al and P (or Si) in the leaves, unlike the other trees. These findings suggested that Al stimulated P, S, or Si accumulation in leaves or Al was transported with P, S, or Si for the Al accumulators ≥3 g kg^-1. No negative relationships between Al and the other 5 elements in the leaves were observed for the Al accumulators ≥3 g kg^-1.     

A comparative study of permeable layer materials and aeration regime on efficiency of multi-soil-layering system for domestic wastewater treatment in Thailand

Abstract

Multi-soil-layering (MSL) system was designed for purifying domestic wastewater and for treating polluted river water. MSL system is typically comprised of layers of soil mixture blocks alternating with permeable layers. The permeable layer has roles of preventing clogging and to increasing the efficiency of infiltration of wastewater through the soil mixture blocks. In this study, the comparative efficiency of five MSL systems as a function of five permeable layer materials (zeolite, zeolitized perlite, perlite, gravel, and charcoal) was investigated. The MSL systems were constructed in 15 × 50 × 100 cm boxes where the soil mixture blocks contained sandy clay soil, kenaf + corncob, and iron scraps at a ratio of 6 : 1 : 1 by weight, respectively, and filled up in alternation with the permeable layer. The results indicated that all the MSL systems at loading rates of 96–346 L m^?2 d^?1 under nonaerated conditions were able to reduce the levels of COD (342–1,231 mg L^?1), BOD₅ (201–802 mg L^?1), and soluble reactive phosphorus (SRP) (3.5–10.1 mg P L^?1) at percentages of 79.0–98.1, 80.0–99.6, and 97.1–100%, respectively. The zeolite and the charcoal-based MSL systems under a 96–346 L m^?2 d^?1 loading rate effectively reduced the level of TN (41.4–65.5 mg N L^?1) at percentages of 79.0–92.1 and 30.7–88.9%, respectively. In terms of prevention of clogging, the charcoal-based MSL system was the most effective, followed by the gravel and zeolite-based MSL. The apparent efficiency of pollutant removal, for zeolitized perlite, perlite, and gravel-based MSL systems was low. With an on-off aeration operation, the efficiency of the MSL systems in the reduction of the levels of COD, BOD₅ , and SRP (hereafter reference to as “removal”) was significantly enhanced. Overall, the zeolite-based MSL system seemed to be more effective than the other MSL systems. However, if optimum aeration could be obtained, the removal efficiency of charcoal-based MSL system might be improved. Aeration at a rate of 64,000 L m^?3 d^?1 for 1 week alternating with 2 weeks of nonaeration enhanced the removal of COD, BOD₅ , and SRP but not that of TN.     

Clarification of water movement properties in a multi-soil-layering system

Maize (Zea mays L.) cv. T42 was grown in refined sand at low (0.1 μM) and normal (30 μu) concentrations of boron each under low (1 mM), normal (4 mM), and excess (8 mM) supply of calcium. Visible symptoms of boron deficiency which appeared first, were accentuated by calcium deficiency and were least evident when calcium was added in excess. The yield was maximum at normal levels of boron and calcium and was the lowest under boron and calcium deficiency.

In maize leaves when both calcium and boron were deficient together the activity of starch phosphorylase increased markedly and that of ribonuclease and polyphenol oxidase also increased. The increase in the calcium content inhibited the starch phosphorylase activity when boron was deficient. The activity of peroxidase was stimulated under boron deficiency at all levels of calcium and that of ATPase was depressed significantly when calcium was deficient alone.

A decrease in the tissue boron (except in old leaves) and tissue calcium content as well as sugar and starch contents was observed under the combined deficiency of calcium and boron.

Excess calcium at both levels of boron increased the tissue boron and calcium contents and decreased the concentration of starch, sugars, nucleic acids, total and inorganic phosphorus, and the activities of starch phosphorylase and ATPase.

The activity of ATPase increased upon the addition of calcium to plants deficient in calcium and boron respectively. The tissue concentration of the element added increased when the element was applied to calcium or boron deficient maize plants.