This study focused on the removal of arsenic from simulated groundwater by batch adsorption using iron-modified rice husk carbon (RH-Fe). The results showed that RH-Fe was very effective in the removal of arsenic not only at low and moderate initial concentrations of arsenic (1.42 and 2.77 mg/L) but also at very high initial concentrations of arsenic (4.61 and 7.38 mg/L). The arsenic adsorption by RH-Fe was dependent on pH and varied with arsenic initial concentration and adsorbent dose. Langmuir isotherm could describe the adsorption equilibrium and the adsorption capacity was found to be 2.24mg/g. The pseudo-second order kinetic model gave the best fit with the experimental data.
Rainwater collected from residential roofs and greywater generated from domestic uses except toilets are viewed as possible substitutes for high grade water sources which supply non-potable indoor uses and irrigation in Australia. This paper searches for alternatives by adopting roofwater and greywater in residential envelope as per Australian water standards. This study provides the results of greywater recycling, which contributes to the greater saving of mains water supply than rainwater use, and which reduces more than half of the wastewater to receiving waters in the rural township of Cranbrook, Western Australia. Similarly, capturing rainwater can mitigate approximately 48% stormwater drainage in this study area. This research endeavours to offer a typical paradigm for an integrated water system in the rural residential sectors.
At present, constant speed pumps and variable speed pumps always run in parallel in pump stations of most water supply companies in China. Research on the frequency control characteristic for the mixed-pump station based on the two-stage optimal operation is performed. Firstly, the ratio of the variable speed pump is calculated inversely according to the outlet pressure of the pump station, and then the speed range can be determined dynamically, so that the variable speed pump can play the role of energy saving as far as possible in safe and rational running status. Secondly, the two-stage optimal operation model for mixed-pump stations of multi-source is established, which is of the operating-mode adaptability, and it is solved by the intelligent genetic algorithm. Furthermore, when the operation mode of multi-source pump stations is transformed, the optimal dispatching of water distribution system in corresponding operation mode can be realized through adjusting the variable parameters in the model. At last, the utility and superiority of the optimal operation method for mixed-pump stations of multiple resources is verified by means of the application in certain urban in China.
Double agar overlay (DAL) method was used to evaluate the inhibition of hydrophytes extracts on coliphages growth by the plaque forming unit (PFU) assay. The present research investigated allelopathic effects of extracts from five hydrophytes leaf, Polygonum hydropiper, Polygonum orientale, Phragmites communis, Arundo donax and Typha latifolia on two coliphages, T4 and f2. The results showed that different hydrophytes inhibit coliphage (T4 and f2) to various extents, and the inhibition of extracts from P. hydropiper was more effective on coliphage T4 and f2 than other hydrophytes. When the concentration of extracts was 0.5g·L-1, the inhibition rate of P. hydropiper leaf on coliphage T4, f2 was 91%, 93%, respectively. The EC50 of P. hydropiper leaf on coliphage T4 was 10mgmiddot;L-1, and the EC50 on coliphage f2 was 12.6mgmiddot;L-1. The EC50 on coliphage T4, f2 of T. latifolia leaf was 16 mgmiddot;L-1, 20 mgmiddot;L-1, respectively. The P. hydropiper showed the greatest inhibition on coliphage. The allelochemicals produced by P. hydropiper should be isolated and evaluated in the following research. More research should be done to evaluate potential use of P. hydropiper in wastewater virus controlling.
In this work, the application of the contact-adsorption-regeneration-stabilization activated sludge process for the municipal wastewater treatment was investigated by using continuous experiments coupled with adsorption batch experiments. The process optimization for performance evaluation was studied. The obtained appropriate operational parameters of recycle ratio, hydraulic retention time (HRT) of the regeneration tank, HRT of the adsorption tank and solids retention time (SRT) of the system were 40%, 2 h, 30 min, and 6 d, respectively. Adsorptive kinetics and equilibrium were investigated with batch experiments of adsorption. The results showed that the activated sludge concentration was in a positive proportion to its adsorptive capability, but that temperature was in an inverse proportion to the adsorptive capability. Adsorptive equilibrium was reached within 15 min. In addition, the equilibrium data fitted well to both the Freundlich and Langmuir adsorption models.
Different types of slag (air-cooled, granulated and carbonated granulated slag) were employed as basal media of eelgrass, Zostera marina L. We investigated how factors such as slag type, particle size and sedimentation of fine particles affected anchorage of eelgrass to the substrates. It was found that eelgrass planted in slag substrates could endure current velocity of 10 to 50 cm s-1. Thus, slag substrates can adequately support and anchor the eelgrass plants even during severe current flow (50 cm s-1). Root establishment and anchorage were also examined by looking at the resistance of the plants to uprooting forces. Results showed that shoots in slag substrates with the finest particle size (<1.18 mm) gave the highest resistance to uprooting among the particle sizes tested (<1.18, 1.18-2.36 and 2.36-4.75mm). Among the slag substrates, shoots in granulated slag pots gave the highest resistance to uprooting. Addition of dredged sediment (DS) or settling of fine particles improved the root establishment, anchorage of eelgrass and root-rhizome extension. However, it was suggested that addition of DS or settling of fine particles to slag may be beneficial to root establishment up to a certain extent only and too much of it might be harmful to eelgrass plants.
Mires are loosing their natural state as a result of human activities. Recently natural Sphagnum mires in Hokkaido, Japan, have been disappearing as a result of the proliferation of alders. Here we show that such proliferation is caused by the inflow of phosphorous compounds as non-point pollutants. Those phosphorous compounds flow in from agricultural fields around mires. The constituents of groundwater or surface water make alders proliferate rapidly. Phosphorous, a typical non-point-polluting nutrient, contributes to the growth of alders, which assimilate atmospheric nitrogen.
The PAHs loadings on river discharge was estimated based on consecutive measurements during rainfall and non-rainfall periods at a river in a suburban area in Hiroshima Prefecture, Japan. The PAH concentrations ranged from 12 to 58 ng L-1 for dissolved PAHs, and from 8 to 105 ng L-1 for particulate PAHs on rainy periods. In non-rainy periods, they ranged from 10 to 58 ng L-1 for dissolved PAHs, and from 4 to 418 ng L-1 for particulate PAHs. PAH concentrations on non-rainy periods were stable for diurnal and seasonal terms. The dissolved PAH concentration was negatively correlated with EC and the particulate PAH concentration was negatively correlated with SS concentration. The yearly loading amount of PAHs was calculated with the data of river flow rate and PAH concentration, and the calculated yearly PAHs specific loading in the River on rainy days was 37 μg m-2 year-1 and the loading in non-rainy days was 29 μg mm-2 year-1. The total loading was 66 ?g m-2 year-1. From these estimations and our previous studies, the atmospheric loadings and river discharge were compared. From the comparison, the order of the loading from river basin area was comparable to this from atmospheric loadings.
We examined the mechanism of alkali soil reclamation by gypsum from the change in hydraulic conductivity and the solute transport in soil. Solute transport mechanism was investigated by using a soil column equipped with tensiometers and four-electrode sensors (FES). Moreover, the pH and EC were measured, and quantitative analysis of the cations (Na+, Ca2+, Mg2+ and K+) and the anion Cl- in leachate was carried out. As a result, the initial Na leaching was confirmed by FES measurement, EC of leachate and quantitative analysis of leachate. Correlation coefficients between all the parameters (pH, EC, cations (Na+, Ca2+, Mg2+ and K+) and Cl-) were confirmed, to different levels of significance (P value ‹ 0.01). Lastly, the water content balance and the evapotranspiration by Penman-Monteith method in the paddy field predicted the soil reclamation time, taking into consideration the meteorological data and the column experimental results. Consequently, it could be predicted that all salts in case of 0.5 wt% application and almost salts (97%) in case of 1.0 wt% application are leached by the end of October.
The effects of ozonation conditions on the performance of a continuous anaerobic/oxic/anoxic (A/O/A) process with sludge ozonation and phosphorus adsorption were investigated. In this system, excess sludge was ozonated by microbubble ozonation, and then the supernatant of the ozonated sludge was flowed into a phosphorus adsorption column packed with zirconium-ferrite adsorbent. The effluent from the column and the settlings of the ozonated sludge were recirculated in the A/O/A process. Long-term operation of a lab-scale system treating rural wastewater showed that ozonation affected not only the sludge reduction efficiency but also the nitrogen removal efficiency. When the amount of sludge to be ozonated was set at 16% of total MLSS per day, no excess sludge was withdrawn, but the nitrogen removal efficiency was deteriorated. Decreasing the amount of sludge to be ozonated (to 9.4% of total MLSS per day) resulted in efficient nitrogen removal, but the MLSS concentration increased slightly. Phosphorus accumulated in the sludge was re-solubilized by ozonation, and a large part of the solubilized phosphorus consisted of Pi. Almost all Pi was recovered in the phosphorus adsorption column.
Macrophyte-cultivated wetlands have a strong potential not only to purify eutrophic water but also to produce biomass resources. Among a variety of macrophytes, we focused on the giant reed (Arundo donax), and its properties of phosphorus uptake, accumulation, and translocation were clarified in this study. Phosphorus uptake experiments using outdoor hydroponic culturing showed the seasonal variation of phosphorus uptake by the giant reed. Furthermore, two kinetic parameters describing the phosphorus uptake by the giant reed were obtained. Phosphorus accumulation experiments using radioactive phosphorus suggested that giant reeds accumulate the absorbed phosphorus in rhizomes, and it is then distributed to the leaves if needed. A phosphorus translocation experiment using radioactive phosphorus indicated that the decreasing of phosphorus in the leaves occurred in the order of location from the bottom to the top, which is relevant to the order of dying down of the plant leaves actually observed in this study. Based on these outcomes, a desirable management method for the giant reed cultivated in wetlands is proposed.