Urban population, it is predicted that, will reach at 5 billion by 2030 and 95% of urban expansion in the next decades will take place in developing countries. In addition, it is indicated that rapid urbanization brings pressures on freshwater supply and sewage treatment. Then sustainable development goal 6 shows 8 targets to ensure availability and sustainable management of water and sanitation for all, and intends to increase proportion of population using safely managed sanitation services, wastewater safely treated and bodies of water with good ambient water quality. Bangkok, which is the capital of Thailand, has 8 centralized sewage treatment plants (CSTP) designed to treat domestic wastewater of approximately a half of residents. However, water quality of some canals in the area provided with sewage works (APSW) has not been improved well, and the cause is not found out due to uncertainty of flows of domestic wastewater. Thus, this study has identified flows of domestic wastewater by an inventory approach to estimate volume of wastewater and biochemical oxygen demand (BOD) discharge based on population distribution in Bangkok. As the results, it is estimated that 75% of BOD discharged in APSW does not reach CSTP.
The environmental risk of the anionic surfactant, linear alkylbenzene sulfonate (LAS), in Japanese surface waters is presented using a probabilistic exposure and effects assessment. A chronic toxicity Species Sensitivity Distribution (SSD) (20 species) is used to define the 5th percentile hazardous concentration and compared to experimental stream mesocosm findings following toxicity normalization to various LAS carbon chain lengths (CL) ranging from C10 to C14. CL-dependent ecotoxicity data are combined with environmental monitoring in Japan where CL distributions of LAS are also quantified. Over 9,000 surface water measurements with CL specific LAS concentrations were compiled. Because LAS displays a common polar narcotic mode of action across all CL, a Toxic Unit (TU) concentration-addition approach can be followed whereby TU exceeding 1 correspond to environmental risk of cumulative Predicted Exposure Concentrations (PEC)/Predicted No Effects Concentration (PNEC) also exceeding 1. SSD, mesocosm, and monitoring data confirm that an extremely small number of water samples exceed a TU of 1 (5 of 4748 for SSD PNEC; 0 sites for mesocosm PNEC). Total LAS measurements from > 25,000 sites were compared to CL normalized PNECs demonstrating > 99.99% probability that the PEC would be less than the PNEC indicating negligible risk from LAS in Japan surface waters.
Eutrophication is a global environmental issue and has been studied for more than 40 years in Atsumi Bay, Aichi Prefecture, Japan. The distribution of nutrients in watersheds and estuaries is strongly influenced by meteorological factors, especially rainfall. Our observations in summer 2010 found that high river discharges during rainfall altered nutrient concentrations throughout the bay, and furthermore resulted in a red tide due to nutrient uptake by phytoplankton. In order to study nutrient dynamics and phytoplankton growth in estuaries, with a focus on the effects of river inputs during rainfall, we developed a depth-averaged two-dimensional ecological model. The model was conceived with the ability to simulate nutrient dynamics, in the form of dissolved nutrient concentrations, and phytoplankton growth throughout an estuary. The model provided reasonable results and agreed well with observed data. Our evaluation showed that the increase in availability of dissolved nutrients and favorable irradiance post-rainfall stimulated production of phytoplankton in the bay, compared to pre-rainfall.
Constructed wetlands are an eco-friendly technology used for decades for treating various types of wastewater. To gain new insight into plant selection for wastewater treatment systems in tropical areas, this research investigated growth and ecophysiological responses of Typha angustifolia to different concentrations of anaerobic digester effluent from a swine farm and assessed their influence on wastewater treatment effectiveness. Twelve plants (n = 4 per treatment) were separately grown in 3 concentrations of wastewater (25% and 50% diluted wastewater and undiluted wastewater). All plants grew well in all concentrations. However, the plants tended to have reduced root biomass, root length and decreased pigment contents when exposed to high concentrations. High removal efficiency for electrical conductivity, total dissolve solids, total suspended solids, biochemical oxygen demand, chemical oxygen demand, ammonium nitrogen and orthophosphate was found (73%, 70%, 93%, 99%, 82%, 99% and 80%, respectively, from undiluted wastewater). The dissolved oxygen concentration in the anaerobic digester effluent increased over time because of released root oxygen. The study showed that T. angustifolia developed aerenchyma in its root cortex even under stress conditions. This ability makes this plant tolerant to high strength wastewater. Furthermore, oxygen released from its roots also supports growth of microorganisms and enhances microbial biodegradation processes leading to highly efficient treatment systems.
The people in Thailand generally soak sticky rice in water for 12–24 h before steaming and rinse jasmine rice before cooking. This study aimed at estimating fluoride intake from rice by the measuring rice consumption and examining factors affecting fluoride adsorption on jasmine rice and sticky rice in Buak Khang Subdistict, Chiang Mai Province, Thailand. It was found that 65.7% of 35 households still use tap water containing fluoride at 5.94 ± 0.29 mg/L of fluoride for rice soaking and rinsing. The amount of jasmine rice and sticky rice consumption was 0.096 ± 0.05 kg/meal and 0.114 ± 0.06 kg/meal, respectively. The fluoride taken up into rice exhibited a positive correlation with the initial fluoride in water, the duration and water volume for rice soaking. The fluoride intake from jasmine rice and sticky rice based on the field survey was 0.004 ± 0.007 mg/kg-bw/day and 0.025 ± 0.024 mg/kg-bw/day, respectively. The results of this study indicated that eating rice can significantly contribute to the total amount of fluoride intake; thus, it is recommended to use fluoride-free water or reducing time duration for rice soaking in areas using fluoride-containing groundwaters.
In this study, Eucalyptus wandoo (EW) biochar and alum sludge and their mixture are used in batches to remove nutrients (ammonium-nitrogen (NH3-N), nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N), and phosphate-phosphorus (PO4-P)) from synthetic stormwater. First, batch tests were conducted using biochar and alum sludge separately with varying concentration (0.5–5 mg/L); dosage (2–10 g); pH (4–9); and contact time (0–24 h). The results revealed that the EW biochar alone could remove 100% of NO2-N and NH3-N while the alum sludge alone could remove 100% of PO4-P. Next batch tests were carried out with the mixture of EW biochar and alum sludge of different proportions and the results revealed that the mixture of 8 g biochar and 2 g alum sludge gave the best combination for removing all nutrients (NH3-N = 98.2%; NO2-N = 99.4%; PO4-P = 99.8%) except NO3-N. The adsorption kinetics of mix-medium were studied for Intraparticle diffusion, liquid film diffusion and Lagergren pseudo first and second-order models. The nutrient adsorptions onto mix-medium show two-stage adsorption process following Intraparticle diffusion and liquid film diffusion. The results revealed that the pseudo-second order kinetic models fitted better with high R2 (0.98–1.00) and small normalized standard deviation, Δq (0.00–0.62). The isotherm results revealed that the NH3-N adsorption followed both Langmuir and Freundlich model while NO2-N and PO4-P adsorption followed Langmuir model better.