Technical and social performances of an arsenic-removal technology—the sono arsenic filter—in rural areas of Bangladesh were investigated. Results of arsenic field-test showed that filtered water met the Bangladesh standard (<50 µg/L) after two years of continuous use. A questionnaire was administrated among 198 sono arsenic filter-user and 230 non-user families. Seventy-two percent of filters (n=198) were working at the time of the survey. Another 28% of the filters were abandoned due to breakage. The abandonment percentage (28%) was lower than other mitigation options currently implemented in Bangladesh. Households were reluctant to repair the broken filters on their own. High cost, problems with maintenance of filters, weak sludge-disposal guidance, and slow flow rate were the other demerits of the filter. These results indicate that the implementation approaches of the sono arsenic filter suffered from lack of ownership and long-term sustainability. Continuous use of arsenic-contaminated tubewells by the non-user households demonstrated the lack of alternative water supply in the survey area. Willingness of households to pay (about 30%) and preference of household filter (50%) suggest the need to develop a low-cost household arsenic filter. Development of community-based organization would be also necessary to implement a long-term, sustainable plan for household-based technology.

Sludge in MBR ProcessSystems Engineering, Faculty of Science and Engineering, MBR (membrane bioreactor) process has been applied to wastewater treatment plants Ritsumeikan University, recently. It is well known that the most important point of the optimum maintenance is 1-1-1 Nojihigashi, control of membrane clogging in the process. Suitable indices for operation and mainteKusatsu, 525-8577, Japan nance in MBR are desired to predict the timely cleaning period and carry out the effective cleaning of the membrane. A large amount of foam is sometimes produced in MBR facilities. Some foam seems to be produced by extracellular protein that is known to cause the membrane clogging. Therefore measurement methodology of foam quality produced by activated sludge in MBR process and characteristics of its extracellular polymer substances (EPS) were studied. The conclusions were: (1) EPS was able to be extracted by steaming treatment on the optimum condition at 105°C for 30 minutes. (2) Bingham viscosity and yield stress of activated sludge were measured. The yield stress was contributed by EPS and this suggested that EPS was one important factor for foaming. (3) The measurement of foam quality using a video camera showed good performance. The foaming power and the foam stability increased proportionally with the concentration of protein in EPS. It was clear that the protein concentration in EPS was strongly related to the foam quality and quantity. (4) The foaming power decreased by addition of MLSS. This decrease was caused by adsorption of EPS to MLSS. Foaming in an aeration tank will be an index for membrane cleaning requirement. Bestimmung der Schaumqualität von Belebtschlamm in Membranbioreaktoren

The control of membrane fouling is an essential issue in membrane bioreactor (MBR) process. It has been recognized that the most important factors that affect membrane fouling are presence of soluble microbial products (SMP) and extracellular polymeric substances (EPS) in a reactor. The objective of this study was to examine the effect of the coagulant addition on the membrane fouling in the MBR process. Accordingly, laboratory scale batch experiments and MBR experiments were conducted using coagulant. In batch experiments, effective SMP removal and control of EPS release were observed by coagulant addition. Fe coagulant was slightly more effective than Al coagulant in the addition of same mole amount. Therefore, Fe was used as coagulant in MBR experiments. In MBR experiments, Fe solutions of 0 mg/L, 2,260 mg/L and 4,520 mg/L were added into the tanks (Run1, Run2 and Run3, respectively) with the flow rate of 200 mL/d. COD removal efficiencies of 97% and phosphorus removal efficiencies of 92% were observed by Fe addition in the MBR experiment. Membrane fouling occurred more often in Run1 than in the other two Runs. Membrane was cleaned 18, 9 and 5 times in Run1, Run2 and Run3, respectively during 40 days runs. This suggested that the membrane fouling was reduced by the coagulant addition. The protein and carbohydrate concentrations of the SMP in the fraction of 1 microm-0.4 microm in Run2 and Run3 were significantly lower than that in Run1 and the particle size of the activated sludge was obviously increased in Run2 and Run3. These results suggested that the coagulant addition is effective to control the membrane fouling.

A simple, low-cost filtration system composed of a ceramic filter, an iron net and iron bacterial sludge was developed to remove arsenic (As) from groundwater. The ceramic filter, made of an 80% clay soil and 20% rice bran mixture on a weight basis, was combined with the iron net and the iron bacterial sludge in a reactor, and the assembly (As removal filter) was tested for its ability to remove As from synthetic groundwater. Synthetic groundwater with a varying composition of As(III), ferrous iron (Fe(II)) and phosphate phosphorus (P) was filtered on a daily basis. The results showed that both Fe(II) in groundwater and those released from the iron net were oxidized biologically and/or physico-chemically and that As and P were effectively removed by adsorption and/or co-precipitation processes. The concentrations of Fe(II) and P in groundwater were decisive factors in the removal of As . Groundwater Fe concentrations of ≥ 2 mg/L and P concentrations of ≤ 3 mg/L with an Fe/P molar ratio of ≥ 3.0 were required to achieve an effluent As concentration of less than 50 µg/L from raw water containing 500 µg/L of As(III). This simple, inexpensive filter could be used to treat As in contaminated regions.

Arsenic removal from ground water by iron oxidizer (Leptothrix spp) was investigated in this study. Batch and column studies were conducted with initial 500 µg/l and 5 mg/l of arsenic and iron, respectively. Batch results showed that 60 % and 51 % As(III) was removed during biological and physicochemical Fe(II) oxidation respectively whereas 96 % As(V) was removed in both cases. On the other hand, 50 % removal of As(V) was observed by adsorption on the iron hydroxides that had been produced after 24 hrs mixing, while As(III) was not adsorbed. It seemed that As(III) were oxidized during biological Fe(II) oxidation and iron oxidizing bacteria itself didn't oxidize As(III) to As(V). Overall As(III) removal efficiency was investigated in a biological sand bed column. Residual arsenic concentrations in the column effluent were always less than 50 µg/l at the flow rate of 7.2 and 3.6 l/d. Phosphorus was also removed very effectively. The sludge analysis showed that the biological iron and arsenic oxidation and their subsequent adsorption were taken place mainly at the top of the column bed. This cost effective technology could be applied to treatment of heavily arsenic and iron contaminated ground water.

This paper presents the recent attention in scientific studies and development of electrochemical processes. Electrochemical technology has contributed significantly to the purification of water for better human health and aquatic life forms. In this study, we emphasize the developmental trends of electrochemical technologies, their applications, and recent developments in the context of water and wastewater treatments. Recent studies have made great advances in investigating and optimizing advanced electrochemical oxidation processes in treatment of various organic pollutants, reduction of halogenated contaminants, and disinfection of microorganisms. Besides, electrochemical oxidation processes have been combined with other treatment methods to enable their practical application. Excellent electro-catalytic treatment of contaminant and their by-products was achieved through the application of mixed metal oxides (PbO 2 , SnO 2 , Ti/RuO 2 , etc.), Pt, and boron-doped diamond (BDD) electrodes. Several studies have focused on selective removal of trace pollutants in a complex matrix. These studies have shown the possibility of removing target pollutants with relatively low energy consumption. It can be concluded that enhancement of treatment performance of the present technologies will contribute to a wider application of electrochemical processes in water and wastewater treatment.

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Addition of coagulant to the activated sludge process is an effective method to remove phosphorus from wastewater. Recently, iron electrolysis method has been developed as a new methodology of addition of coagulant into the activated sludge process. Although this process has been applied to industrial wastewater treatment plants or small-scale domestic wastewater treatment plants, the phosphorus removal performance by iron electrolysis combined with full-scale activated sludge process has not been clear yet. The objective of this study is to investigate the phosphorus removal efficiency by iron electrolysis combined with the activated sludge process. The enhanced biological phosphorus removal took place and phosphorus removal efficiency was increased without iron addition because of the occurrence of anaerobic condition in the surveyed wastewater treatment plant. Phosphorus removal performance in the investigated wastewater treatment plant was improved by the iron electrolysis. Effluent phosphorus concentration was decreased below 1.0 mg/L with additional iron of Fe/P molar ratio 0.4. The theoretical weight of iron release agreed with the actual weight decrease of iron electrodes. The introduction of iron electrolysis to the activated sludge process could enhance the phosphorus removal efficiency without any effects on substrate removal performance and make the phosphorus removal to be stable and sustainable.