Quantitative risk assessment for reclaimed wastewater irrigation on paddy rice field in Korea

Water shortage has become an important issue for Korean agriculture. Korea suffers from a limited agricultural water supply, and wastewater reuse has been recommended as an alternative solution. This study examined the concentrations of toxic heavy metals and Escherichia coli in a paddy rice field irrigated with reclaimed wastewater to evaluate the risk to farmers. Most epidemiological studies have been based on upland fields, and therefore may not be directly applicable to paddy fields. In this study, a Beta-Poisson model was used to estimate the microbial risk of pathogen ingestion. The risk value increased significantly after irrigation and precipitation. The results of the microbial risk assessment showed that risk values of groundwater and reclaimed wastewater irrigation were lower than the values of effluent directly from wastewater treatment plants. The monitoring results of heavy metals for each irrigated paddy fields did not show specific tendency. A risk assessment for toxic heavy metals was performed according to various exposure pathways; however, the results of the carcinogenic and noncarcinogenic risk estimation showed that the risk from reclaimed wastewater-irrigated paddy fields was the lowest.     

A review on microbial and toxic risk analysis procedure for reclaimed wastewater irrigation on paddy rice field proposed for South Korea

Water shortage has become a major agricultural concern, and “The Sustainable Water Resources Research Program” in Korea is currently addressing this problem through the development of treatment systems for reclaiming wastewater and the assessment of human health risks associated with its reuse. Through this program, started in 2001, many studies have examined various water resources. Reclaiming wastewater is one way to alleviate water-shortage pressures, and one of the major potential uses of reclaimed water is irrigation. However, the main concern with reusing reclaimed wastewater is the increased likelihood of human contact that might result in exposure to pathogens and increased health risks. Relatively few studies have examined the toxic risks using reclaimed wastewater for irrigation in rice paddy fields. This study provides an overview of methods for quantitative microbial risk assessment and toxic risk assessment of heavy metal concentrations developed in the previous studies that can be applied to the evaluation of rice paddy fields irrigated with reclaimed wastewater in South Korea.     

Development of natural and ecological wastewater treatment system for decentralized community in Korea

A pilot study of the natural and ecological wastewater treatment system (NEWS) was performed to treat sewage in decentralized small rural communities in Korea. The absorbent-biofilter system (ABS) provided secondary level pretreatment and demonstrated high removal efficiency especially for SS and BOD₅ showing 88.5 and 82.9%, respectively. The influent and effluent concentrations of TN were 42.1 and 26.2 mg L⁻¹, respectively, with the removal efficiency of 37.8%. In case of TP, the removal efficiency was 45.1% with the influent and effluent concentrations of 3.1 and 1.7 mg L⁻¹. The ABS effluent could not meet the effluent standards, and the further treatment was required. The subsequent up- and down-flow constructed wetland (UDCW) provided further polishing of the ABS effluent and demonstrated effective removal of nutrients as well as SS and BOD₅ with over 70% removal rates. Overall performance of the NEWS, which was composed of ABS and UDCW, demonstrated remarkably high removal rates for BOD₅ (>95.7%), SS (>97.5%), TN (>91.8%) and TP (>90.1%) and met all the effluent standards stably independent of temperature and influent loading in the experimental range. The UDCW used light and porous granular substrate (∅ 5–10 mm, specific gravity of 1.2) with large surface area, and clogging problem was not observed during the study period. The system was cost effective and required minimal maintenance and negligible amount of electricity, and problems associated with noise, odor, files, and sludge were not observed. Considering characteristics of decentralized wastewater treatment systems, the NEWS system was found to be a practical alternative and its application is recommended up to 300 m³ day⁻¹. The NEWS system has an economic problem above 300 m³ day⁻¹, because of complicated equipment, higher operation costs, and maintenance specialists. The NEWS system was coast effective and required minimal maintenance and negligible amount of electricity, and problems associated with noise, odor, files, and sludge were not observed.     

汉沽管理区农田水利发展状况

揭示出汉沽管理区地理位置和自然旱灾引起的海水倒灌、地上水盐分超标,以及地下水开采超量等原因所造成的水少、水暴、水脏三大问题,启示人们应从全局和战略高度提高认识,加强农田水利基本建设。并总结了近年来管理区农田水利发展的经验,提出了今后的发展规划。     

汉沽管理区农田水利发展状况

揭示出汉沽管理区地理位置和自然旱灾引起的海水倒灌，地上水盐分超标，以及地下水开采超量等原因所造成的水少、水暴、水脏三大问题，启示人们应从全局和战略高度提高认识，加强农田水利基本建设。并总结了近年来管理区农田水利发展的经验，提出了今后的发展规划。     

Influence of saltwater wedges on irrigation water near a river estuary

Paddy and Water Environment - Paddy fields irrigated using water from the Shinkawa River in Niigata, Japan, are subject to adverse effects associated with the occurrence of saltwater wedges in the...     

污水灌溉对小麦幼苗生理特性及抗氧化酶活性的影响

用不同浓度的污水分别对小麦幼苗进行处理,测定其根系活力、细胞膜透性、超氧化物歧化酶（SOD）活性、过氧化氢酶(CAT)活性、过氧化物酶(POD)活性及丙二醛（MDA）含量。研究了污水对小麦生理特性及抗氧化酶活性的影响。结果表明：随着污水处理浓度的提高,根系活力不断降低,细胞膜透性不断升高, SOD、CAT及POD活性均表现为先升后降的趋势, MDA的含量呈逐渐上升的趋势。     

Feasibility of SRI methods for reduction of irrigation and NPS pollution in Korea

An experimental study on the System of Rice Intensification (SRI) methods was conducted to investigate the feasibility of using them to conserve irrigation water and reduce non-point source (NPS) pollution in Korea. Eight experimental runoff plots were prepared at an existing paddy field. Runoff and water quality were measured during the 2010 growing season in which a Japonica rice variety was cultivated. The irrigation water requirements of SRI methods and conventional (CT) plots were 243.2 and 547.3 mm, respectively, meaning that SRI methods could save 55.6% of irrigation water. Runoff from SRI methods plots decreased 5–15% compared with that from CT plots. Average NPS pollutant concentrations in runoff from SRI methods plots during rainfall-runoff events were SS 89.4 mg/L, COD_Cr 26.1 mg/L, COD_Mn 7.5 mg/L, BOD 2.0 mg/L, TN 4.2 mg/L, and TP 0.4 mg/L. Except for COD_Cr and TN, these concentrations were significantly lower than those from CT plots. Measured pollution loads from SRI methods plots were SS 874 kg/ha, COD_Cr 199.5 kg/ha, COD_Mn 47 kg/ha, BOD 13 kg/ha, TN 36.9 kg/ha, and TP 2.92 kg/ha. These were 15.8–44.1% lower than those from CT plots. Rice plants grew better and healthier in SRI methods plots than in CT plots. However, rice production from SRI methods plots ranged between 76 and 92% of that of CT plots because the planting density in SRI methods plots was too low. It was concluded that SRI methods could be successfully adopted in Korea and could help save a significant amount of irrigation requirement in paddies and reduce NPS pollution discharge.     

Effects of olive oil mill wastewater used as irrigation water on in vitro pollen germination

The aim of this study is to assess the effects of Olive Oil Mill Wastewater (OOMW) application as irrigation water on in vitro pollen germination, focusing on total protein quantity. In test groups, pollen germination substances such as sucrose, H3BO3 and Ca(NO3)2 were added to different concentrations of OOMW and used as germination media. Regarding control group, the same substance melted into water instead of OOMW. As a result, in general, pollen germination percentage was decreased significantly in all OOMW concentrations than that of the control group, except 1/1000 concentrations. Similarly, total protein quantities declined linearly depending on decreasing OOMW concentrations, except 1/1 concentration which has 4-5 times the control value. Consequently, it was established that OOMW generally decreased pollen germination ratio and had carcinogenic effects on protein synthesis mechanism and must not be used as irrigation water without purification.     

Economic assessment of water-saving irrigation management techniques and continuous flooded irrigation in different rice production systems

Paddy and Water Environment - Globally, increasing water scarcity and higher production costs are the challenges in the cultivation of conventional transplanted rice (TPR). Under such conditions,...     

Delivery management water requirement for irrigation ditches associated with large-sized paddy plots in Korea

Delivery management water requirement (DMWR) is the use of bypass water in paddy field irrigation to help maintain desired water levels in irrigation canals and to distribute water to paddy plots in a uniform manner. Diverted irrigation water (DIW), DMWR, and the DMWR/DIW ratio were investigated for concrete lined irrigation ditches with large-sized paddy plots (100 m×100 m) during irrigation periods (May to mid-September). DIW and DMWR were measured at 5- to 10-day intervals at the inlets and outlets of irrigation ditches on stable water supply days. The mean DMWR/DIW ratios in irrigation ditches L₁ and L₂ over 3 years were 36 and 34%, respectively. The mean DMWR/DIW ratios displayed month-to-month and year-to-year variation. The monthly mean DMWR/DIW ratios were highest (55 and 71%) in June and lowest (<20%) in August and September. The annual mean DMWR/DIW ratios during a dry year markedly decreased to 11%, compared with 42% in other years. The decrease was due to the small DIW and farmers water management to maximize capture of limited irrigation water during the drought. The DMWRs in May and June were significantly (p<0.01) correlated with the DIWs, indicating that high DMWR in May and June are attributed to excessive DIW.     

A GIS-based framework of regional irrigation water demand assessment

Although a lot of research has been performed on estimating irrigation water demand at the on-farm level, far less has been done on irrigation water demand for a region-wide basis, such as for a river basin or an area covering multiple river basins. The capture and management of the spatial variations in related data such as soil, climate, crops, and canal networks is the key to effective and efficient regional irrigation water demand estimations. The Geographic Information System (GIS), with its powerful spatial data management and analysis capabilities is used in this study to extend the scope of on-farm irrigation water estimation into a regional estimation. A command area covering several river basins in southern Taiwan was used to build a model prototype. The model framework shows the capability of the system to estimate regional irrigation water demand with most of the spatial variations preserved. The model also shows the capability for quickly reflecting changes in irrigation water demand in response to changes in cropping patterns, a feature that may be a necessary for regional water resource planning.     

Uncertainty of paddy irrigation requirement estimated from climate change projections in the Geumho river basin, Korea

Despite evidence from numerous studies that over-reliance on a single General Circulation Model (GCM) could lead to inappropriate predictions or adaptation responses to climate change, single GCMs are still used in most mesoscale impact assessments. The objective of this article was to analyze the uncertainty associated with the use of multiple GCMs on future climate change impact assessments on the paddy irrigation water requirements in the Geumho river basin, Korea. Climate projections were extracted for 13 GCMs from the Intergovernmental Panel on Climate Change (IPCC) for A2, A1B, and B1 scenarios, downscaled using the change factor method and were then analyzed. The Food and Agricultural Organization CROPWAT model was used to calculate the paddy irrigation water requirements. Reference evapotranspiration and the crop water requirements were predicted to increase in future periods (2030s, 2055s, and 2090s). Rainfall predictions from the different GCMs exhibited high variability. The projected mean (range) of the paddy irrigation water requirement increase was 1.1% (?9 to 15%), 2.4% (?9 to 13%), and 7.9% (?4 to 24%) for the 2030s, 2055s, and 2090s, respectively, compared to the baseline values (1975s). The predicted irrigation water requirements for the future were shown to have a relative standard deviation of up to 7.1%. Regression analysis was performed on the trends of predicted water requirement over time using the coefficient of determination. It was concluded that multiple models should be used where possible to avoid inappropriate planning or adaptation responses particularly in the short term. Adaptation strategies are required to mitigate the future impact of increasing future water demand.     

Probabilistic risk assessment of agrochemicals in the environment

Concern for the environment has resulted in greater scrutiny of both old and new plant protection products and increased efforts have been directed to developing more rigorous but more realistic procedures for the ecotoxicological risk characterization of these agrochemicals. These techniques include probabilistic analysis of toxicity and exposure data and better understanding of the relationship between structure and function in populations of wildlife and the role of keystone species in maintaining ecosystem functioning. The ecological risk assessment method described here is centered on the use of probabilistic distribution functions that independently describe exposure concentrations and toxicological responses of organisms to the chemical of concern. The distributions are transformed to permit calculation of linear regression parameters. The regression parameters for the two distributions are then used to determine joint probabilities which interrelate the exposure and toxicology data. For ease of presentation the results are presented as an exceedence plot which depicts, based on the exposure data the percent of species likely to be affected and the percent of observations likely to cause this level of effect. In this paper, the use of the method is illustrated using data for chlorpyrifos in North American aquatic environments. These probabilistic risk assessment methods are being assessed for incorporation into assessment procedures in a number of regulatory jurisdictions.     

Economic impact assessment in pest risk analysis

According to international treaties, phytosanitary measures against introduction and spread of invasive plant pests must be justified by a science-based pest risk analysis (PRA). Part of the PRA consists of an assessment of potential economic consequences. This paper evaluates the main available techniques for quantitative economic impact assessment: partial budgeting, partial equilibrium analysis, input output analysis, and computable general equilibrium analysis. These techniques differ in width of scope with respect to market mechanisms (relationships between supply, demand, and prices), and linkages between agriculture and other sectors of the economy. As a consequence, techniques differ in their ability to assess direct and indirect (e.g. economy-wide) effects of pest introduction. We provide an overview of traits of the available methods to support the selection of the most appropriate technique for conducting a PRA. Techniques with a wider scope require more elaborate data, and greater effort to conduct the analysis. Uncertainties are compounded as methods with greater scope are used. We propose that partial budgeting should be conducted in any risk assessment, while more sophisticated techniques should be employed if the expected gains in insight outweigh the costs and compounded uncertainties.     

应用酵母菌在味精废水中COD处理的影响因素分析

根据味精废水的水质特点研究了酵母菌处理味精生产废水中对COD的影响。考察Tpn值、温度和发酵时间对酵母菌处理味精生产废水中COD的去除效果。结果表明,酵母菌对于环境条件的要求很宽松,应用酵母菌处理味精废水具有良好的环境和经济效益。     

转基因花生外源基因田间漂移风险初步研究

用含花生条纹病毒壳蛋白(cp)基因和潮霉素(hygr)筛选基因的转基因花生品系为材料,田间试验表明转基因花生中的hygr基因可在短距离范围内随花粉漂移,离转基因花生种植区边缘1.0m 和3.0m范围内漂移频率分别为4.4%和5.0%;3.0 m以外范围内,没有检测到hygr基因随花粉漂移发生。各距离范围内均没有检测到cp基因随花粉漂移现象。因此认为,转基因花生外源基因漂移距离在3.0m以内。     

Modeling risk analysis for rice production due to agro-climate change and uncertainty in irrigation water

Paddy and Water Environment - This study proposes a risk analysis model for quantifying the insufficient risk of rice production due to the climate change and variation in irrigation water and...     

High yield and nutritional quality of rice for animal feed achieved by continuous irrigation with treated municipal wastewater

Paddy and Water Environment - Two consecutive pilot-scale experiments were conducted to investigate the potential reuse of treated municipal wastewater (TWW) as an irrigation source for cultivating...