Naoyuki Funamizu

Effect of Moisture Content on the Composting Process In a Biotoilet System

Biotoilet is a composting toilet that uses sawdust as a matrix for bioconversion of human excreta into compost and is managed with the aim of accelerating decomposition, optimizing efficiency, and minimizing any potential environmental problems. Understanding how the moisture content affects the biodegradation rates of feces is a key factor for setting criteria for the proper design and operation of the biotoilet. A research project in this respect was conducted in laboratory-scale composting reactors. Results showed that composting is characterized by different biological responses of microorganisms depending on the moisture content under which the process is conducted. Low moisture contents (< 64%) ensure aerobic degradation of feces, whereas high moisture levels (> 64%) cause both aerobic and anaerobic decomposition. Higher reductions in parameters such as total solids (TS), volatile solids (VS), and chemical oxygen demand (COD), and higher oxygen utilization rates were obtained at moisture contents near 65%. This moisture level is the critical moisture estimated during drying tests on sawdust. At high moisture contents, odors, anaerobic emissions, nitrite formation, and increase of sulphate concentrations were detected. Keeping moisture content near 60%, or little higher, but avoiding levels near or higher than 65% ensures an optimum performance of the biotoilet system.

Nitrous oxide emission mechanisms during intermittently aerated composting of cattle manure.

To investigate the mechanisms of nitrous oxide (N₂O) emission during intermittent aeration in the composting process, a laboratory scale experiment with continuous measurement of N₂O emission was conducted with cattle manure. A low oxygen mode (2.5% oxygen in the inlet for 1 day), anaerobic mode (0.13% oxygen for 0.25 day), and aerated mode (20.5% oxygen for 2 days) were sequentially set up three times after 22 days of continuous aeration to replicate intermittent aeration. The total N₂O emission was 0.26-0.35 mmol, 0.27-0.32 mmol, and 0.14-0.23 mmol during the low oxygen, anaerobic, and aerated modes, respectively. Denitrification was indicated as the main N₂O emission pathway in the anaerobic and low-oxygen modes, while nitrification was indicated as the main pathway in the aerated mode and under continuous aeration. Results from this study suggest that nitrification is an important pathway for N₂O emission as well as denitrification.

Incorporation of the concept of microbial product formation into ASM3 and the modeling of a membrane bioreactor for wastewater treatment

This paper proposes a modification of ASM3 in a way that takes into account the process of production and consumption of microbial products (MPs) in a submerged membrane bioreactor fed with the effluent of a particular precoagulation sedimentation unit. A comparative representation of the modeling results obtained with ASM3 and ASM1 is performed and it highlights the importance of considering the process of storage of organic substrate, including MPs, as a prior step to bacterial growth. In addition to the suspended solids and microorganisms, various soluble organic substances, which might be either undecomposed organic substances contained in the raw water or MPs, are assumed to be selectively retained within the bioreactor. The results show that the carbonaceous materials are more accurately estimated by ASM3, while ASM1 performs slightly better than ASM3 in the estimation of nitrate. The estimated MP concentration in the mixed liquor and permeate agrees with the experimental evidence, and as expected, MPs play a role in supplying organic substrate to heterotrophs in both ASM1 and ASM3.

Photocatalytic decomposition of crotamiton over aqueous TiO2 suspensions: Determination of intermediates and the reaction pathway

The photocatalytic degradation of crotamiton in aqueous solution using TiO(2) was investigated. To investigate the effect of initial pH, the photodegradation behaviors of three types of pharmaceuticals were compared (crotamiton, clofibric acid, sulfamethoxazole). The degradation rates of crotamiton in the pH range 3-9 were nearly equal, but those of clofibric acid and sulfamethoxazole were affected by pH. At pH>6.5, TiO(2) particles, clofibric acid and sulfamethoxazole had negative charge, therefore, the repulsive force between TiO(2) particles and anionic pharmaceuticals occurred and a low reaction rate at high pH was observed. The effect of UV intensity and TiO(2) concentration on photodegradation efficiency was also investigated. Linear and logarithmical relationships between UV intensity, TiO(2) concentration and the reaction rate constant were confirmed. Furthermore, the structures of photodegradation intermediates formed concomitantly with the disappearance of crotamiton were estimated. Seven intermediates were characterized by LC/MS/MS analyses, and it was assumed that the photocatalytic degradation of crotamiton was initiated by the attack of electrophilic hydroxyl radicals on aromatic rings and alkyl chains.

An improved Richardson-Zaki formula for computing mixed layer composition in binary solid-liquid fluidized beds

In a liquid fluidized bed consisting of binary solid particles differing in size and density, the mixing of the two kinds of particles occurs and the degree of mixing is controlled by an equilibrium force balance relationship. A model to predict the volume fractions of particles in the mixed layer is developed in this paper on the basis of the force balance relationship of each particle species. In describing the drag forces of particle components 1 and 2 in a mixed layer, two hypothetical mono-component beds, bed (1∗) and bed (2∗), are introduced. The bed (i∗) (i=1,2) consists of only one particle component i, and it is assumed that the drag force acting on the particle component i in this bed is equal to that acting on component i in the mixed layer. This assumption, coupled with the Richardson and Zaki formula, leads to a modified Richardson and Zaki formula for computing the composition of the mixed layer in a binary solid-liquid fluidized bed. The validity of this model is tested against experimental data.

Occurrence of Hand-Foot-and-Mouth Disease Pathogens in Domestic Sewage and Secondary Effluent in Xi'an, China

Hand, foot and mouth disease (HFMD), caused by a group of enteric viruses such as Enterovirus 71 (EV71), Coxsackievirus A16 (CVA16) and Coxsackievirus A10 (CVA10), is heavily epidemic in East Asia. This research focused on investigating the occurrence of HFMD pathogens in domestic sewage and secondary effluent before disinfection in a wastewater treatment plant (WWTP) in Xi’an, the largest megacity in northwest China. In order to simultaneously detect all three HFMD pathogens, a semi-nested RT-PCR assay was constructed with a newly designed primer set targeting conservative gene regions from the 5′ untranslated region (UTR) to VP2. As a result, 86% of raw sewage samples and 29% of the secondary effluent samples were positive for the HFMD viral gene, indicating that HFMD pathogens were highly prevalent in domestic wastewater and that they could also persist, even with lower probability, in the secondary effluent before disinfection. Of the three HFMD pathogens, CVA10 was positive in 48% of the total samples, while the occurrences of CVA16 and EV71 were 12% and 2%, respectively. It could thus be stated that CVA10 is the main HFMD pathogen prevailing in the study area, at least during the investigation period. High genetic diversity in the conservative gene region among the same serotype of the HFMD pathogen was identified by phylogenetic analysis, implying that this HFMD pathogen replicates frequently among the population excreting the domestic sewage.

Strategies toward commercial scale of biosurfactant production as potential substitute for it's chemically counterparts

In the past few decades natural emulsifiers/biosurfactants have been intensively studied for their ability as potential substitute for synthetic surfactant usage. Biosurfactants are valuable microbial amphipathic compounds with effective surface active and biological properties which are applicable to several industries and process materials. Several biosurfactants properties are low toxicity, higher biodegradability and ecological acceptability, also synthesised from wide range of raw materials. At present, biosurfactant are unable to compete with the synthetic surfactant due to their high production cost, specific functionality and production capacity to meet the need of intended applications. A considerable number of researches and studies have been published in order to eliminate the economical bottleneck of biosurfactants production process. This review describes alternatives strategies toward commercialisation of biosurfactants on a large scale that might be able to replace their chemical counter parts.

A minimal potential energy model for predicting stratification pattern in binary and ternary solid-liquid fluidized beds

Predicting the stratification pattern of a binary or ternary solid-liquid fluidized bed requires not only the calculation of the volume fractions of particles in mixed and mono-component layers but also the specification of the order and the thickness of the layers in the bed. A model was developed for such prediction on the hypothesis that the total potential energy of particles in a bed is minimal. Experiments were carried out for a solid system consisting of glass beads, activated carbon and acrylic particles. The experimental results verified the predicted stratification patterns computed on the basis of the hypothesis adopted in this study.

Comparison between treatment of kitchen-sink wastewater and a mixture of kitchen-sink and washing-machine wastewaters.

In this paper, a submerged membrane bioreactor was used to treat ‘higher‐load’ grey water: a) kitchen‐sink wastewater only, and b) a mixture of kitchen‐sink wastewater and washing‐machine wastewater. For each type of wastewater, three systems operated at different hydraulic retention times (HRTs) were investigated. In the mixture of kitchen‐sink wastewater and washing‐machine wastewater, the reactor with a short HRT of four hours was stopped due to foaming. It has been observed that for both types of wastewater, an HRT of eight hours or longer can be used for the treatment. However, it has been observed that a higher COD in the permeate of the mixture can be obtained compared with that of the kitchen‐sink wastewater only. This indicated that washing‐machine wastewater has some component that is not easily biodegradable. The total linear akylbenzene sulfonate (LAS) removal was > 99% even at a concentration of 10–23 mg l−1.

Simulation of the operational conditions of the full-scale municipal wastewater treatment plant to improve the performance of nutrient removal

Simulation analysis based on a mathematical model is one of the powerful tools for determining the operational conditions for a full scale biological nutrient removal plant. The model that included the Activated Sludge Model No.2 was developed for simulating the performance of the plant in Sapporo City. The investigated plant has the biological reaction basin which consists of the four zones, anaerobicaerobic-anoxic-aerobic phases with the step feed of the primary effluent to the anaerobic and anoxic zones. We performed three experiments to calibrate and verifY our model: (i) Characterization of organic matters in the influent with the OUR test; (ii) Measurement of COD and nutrient concentration at the plant; (iii) Lab-scale batch experiments with the anaerobic-aerobic-anoxic-aerobic phases. The calibrating process showed that no modification of parameter values was required to evaluate the performance and population of the activated sludge. Simulated results showed that the choice of the sewage step feed ratio did not affect the nitrogen removal and that the denitrification rate in the anoxic zone was controlled by the hydrolysis rate of the slowly biodegradable organic matters. The results of the lab-scale experiment and simulation showed that the addition of the readily biodegradable organic matters like fermentation products of the primary settler sludge was effective to improve the performance of nitrogen removal.