Hidenori Harada

Worldwide surveys of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in water environment in recent years

Recently, perfluorinated compounds (PFCs) have been noted as causes of some of the important environmental problems in recent years due to their occurrences and properties. The most commonly used PFCs are perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), which have been used in many kinds of products. They have been found in surface water and tap water in both developed and developing countries around the world including in North America, Europe and Asia. In most countries, rivers are the source of tap water, which is one of the important pathways in which PFCs reach humans. It is essential to evaluate PFOS and PFOA contamination in the river basin. The purpose of this field study was to determine the presence of PFOS and PFOA in rivers around the world. The surveys were conducted in 15 countries during 2004 to 2010. In total, 539 samples were collected from the rivers in 41 cities. A solid phase extraction (SPE) coupled with HPLC-ESI-MS/MS were used for the analysis of these chemicals. PFOS and PFOA were detected in all 41 cities not only in industrialized areas but also in non-industrialized areas, representing that these compounds undergo long-range transportation in the environment. The average concentration of PFOS in each city ranged from not detected to 70.1 ng/L. The average concentration of PFOA in each city was in the range 0.2-1,630.2 ng/L. The industrialized areas show higher contamination in both PFOS and PFOA concentrations than non-industrialized areas. Industrial activities are some of the major sources of PFCs contamination in rivers.

A measure for provisional-and-urgent sanitary improvement in developing countries: septic-tank performance improvement

Although many cities have planed to develop sewerages in developing countries, sewerage establishment still requires huge investment and engineering efforts. Improvement of existing sanitation facilities may contribute the betterment of urban sanitation before sewerage establishment. The purpose of this study is to propose a measure to improve urban sanitation in areas where a sewerage development plan is proposed but has not been yet established, based on a case study in Hanoi, Vietnam. We found that 90.5% of human excreta flowed into septic tanks. However, 89.6% of septic tanks have never been desludged in the past and their performance was observed to be at a low level. The study also showed that if they introduce regular desludging with a frequency of once a year, they can eliminate 72.8% of COD loads from septic tanks. It was indicated that the performance can be dramatically recovered by regular desludging, which could contribute urban sanitation improvement in Hanoi. In conclusion, the performance recovery of septic tanks by regular desludging was proposed as a provisional-and-urgent measure for urban sanitation improvement, together with the septage treatment in sewage sludge treatment facilities, which should be established earlier than other facilities of sewage treatment systems.

ベトナム国ハノイ市郊外集落における排水・廃棄物管理とその影響 : 窒素・リンフロー分析

Hanoi, the capital of Vietnam, is facing rapid modernization, leading to the improper management of waste and wastewater. The purpose of this study was to evaluate the impacts of waste and wastewater management on water environment, in terms of nitrogen and phosphorus flows. Trai hamlet, located in the south part of Hanoi, was selected as a research community. A waste and wastewater stream survey was implemented by a door-to-door interview for 100 households. A material flow model of nitrogen and phosphorus was developed with focus on sub-urban waste and wastewater management. Then, the model was applied for the study area. The results showed that the component receiving the largest amount of nutrients was paddy field, 435.1 kg-N/ha/year and 89.8 kg-P/ha/year, in which 40% of N and 65% of P were derived from chemical fertilizer. Although waste and wastewater recycling is widely implemented, the management of pig liquid waste is a serious problem in this area since most of them were discharged directly to the water bodies. The total nutrient loads to the water bodies in 2010 was 187.3 kg-N/ha/year and 13.4 kg-P/ha/year, of which paddy field accounted for 70% of nitrogen and fish pond did for 60% of phosphorus.

Cross-country analysis of faecal sludge dewatering

ABSTRACT Dewatering of faecal sludge (FS) is indispensable for adequate FS management. However, comprehensive knowledge is lacking on FS dewatering performance. This study compared the dewatering performance of FS from different countries and onsite sanitation technologies, to assess influential characteristics on dewatering, and to compare dewatering performance of FS with wastewater sludge. We collected 73 FS samples from septic tanks, lined pit latrines, unlined pit latrines and johkasou tanks in Uganda, Vietnam and Japan, and 18 samples of wastewater sludge in Switzerland. Capillary suction time (CST) and total solids (TS) of centrifuged sludge (%TSfinal) were determined as metrics of dewatering rate and dewaterability, respectively, together with relevant sludge characteristics. Data were analysed by bootstrapping comparison of median results of each sample category and by bootstrapping multiple regression analysis to quantify the relative importance of sludge characteristics on dewatering performance. Results showed that the dewatering rate was significantly different between FS from different technologies, whereas dewaterability was significantly different within the same technology. FS had a significantly lower dewatering rate than wastewater sludge. In contrast, FS dewaterability was greater than wastewater sludge. However, this could be attributed to higher concentrations of sand in FS. Electrochemical properties such as NH4-N and surface charge had the strongest correlation to dewatering rate, and solid properties such as sand content and total volatile solids to dewaterability. The results identify potential characteristics that could explain and predict the high variability of FS dewatering performance that is observed in the field.

Incremental sanitation improvement strategy: comparison of options for Hanoi, Vietnam.

Urban sanitation issues should be tackled strategically, and may be addressed effectively when sewage development is pursued in conjunction with complementary sanitation measures. Five sanitation improvement scenarios employing sewage, night-soil collection-and-treatment (NSCT) system, and/or septic-tank improvement by annual dislodging were analyzed from the perspective of COD loads, total nitrogen loads, and cost under the conditions found in Hanoi, Vietnam. Compared to the development of sewage alone, the scenario of developing NSCT systems in a complementary manner with sewage development was estimated to be the most effective for a rapid decrease of both COD and total nitrogen loads. However, it may be difficult in some cases to replace ordinary water-flush toilet by the micro-flush toilet that are used in NSCT systems. In this case, the scenario employing septic-tank improvement in conjunction with sewage development may be effective for a rapid decrease of COD in locations where septic tanks are widely used under poor maintenance conditions and nitrogen pollution is not serious compared to COD. It was calculated that the two scenarios above would respectively require cost increases of 16 and 22% over the sewage development scenario.

Enhancement of Biogas Production from Anaerobic Digestion of Disintegrated Sludge: A Techno-Economic Assessment for Sludge Management of Wastewater Treatment Plants in Vietnam

Currently, in Vietnam 35 urban WWTPs had been constructed with a total capacity of 850,000 m3/day. Some 40 new WWTPs are in the design or construction phase with a capacity of 1,600,000 m3/day. During operation, a lot of excess sludge must be wasted out of the system. It is well recognized that sludge disposal is one of the most critical issues for WWTPs as the cost of the excess sludge treatment and disposal can account for 50–60% of the operating cost. In Vietnam, sludge discharged from wastewater treatment plants were mostly disposed by the conventional method such as landfill. Therefore, reduction of sludge volume before disposal is very important for sludge transportation and management. In this study, the sludge was disintegrated by alkalis to enhance the sludge biodegradability before adding to the anaerobic digestion. As a result, MLSS reduced from 6600 mg/L down to about 4800 mg/L when alkalis dosage was increased from 1 to 1.8 g/L. Soluble COD was increased from less than 100 mg/L to over 1800 mg/L. The sludge biodegradability enhancement is linearly correlated to COD solubilization. The biogas production of the disintegrated sludge was higher compared to the sludge without the alkali disintegration (358 and 245 mL biogas/g sludge added), representing a 46% increase in the biogas production. The cost of chemical consumption for sludge disintegration was about 0.36 US

Urine-Diverting System for Securing Sanitation in Disaster and Emergency Situations

/kg TSS. The alkali sludge disintegration combined with anaerobic digestion process could be considered as a potential approach for sludge management of wastewater treatment plants in Vietnam.

Predicting struvite formation for phosphorus recovery from human urine using an equilibrium model

AbstractBecause securing sanitation was one of the great concerns after the Great East Japan earthquake of 2011, the writers developed a disaster-responsive portable toilet unit modeled after urine-diverting toilets. The unit, which separates urine and feces, is produced from ready-to-assemble plastic cardboard, which facilitates transportation and stocking. The separated feces are processed without any water and electricity using a mixture of lime and carbonized rice husks or dry soil, which promotes the drying and alkalization of feces for disinfection and deodorization. The urine may be discharged without treatment because it contains few pathogens. By July 2011, 54 units had been provided to the disaster-affected areas of East Japan, where they have been evaluated positively and acquired for future preparedness. This paper describes the development of this portable toilet unit and proposes a disaster responsive and environmentally friendly system for routine use in public buildings that, in emergencie...