Kenji Furukawa

Nutrient removal from secondary effluent by filamentous algae

Abstract The nutrient removal potential of filamentous Oscillatoria sp. was quantitatively studied. Oscillatoria sp. showed satisfactory growth on secondary activated sludge effluent supplemented with 1% NaHCO3. Continuous open culture of Oscillatoria sp. was kept stable using a continuous stirred tank equipped with a filter-separator. Kinetic constants YN and YP were 10.6 g cells/g NO3-N and 37.7 g cells/g PO43− respectively through the analysis of the results of continuous culture experiments. Monoalgal continuous culture of more than 90% purity could be maintained for 6 months without contamination. The harvested Oscillatoria cells were proven to have an excellent filterability. They also have excellent autoflotation. The amino acid composition of the Oscillatoria algal protein compares favorably with the tentative standard for ideal protein defined by FAO/WHO.

Autotrophic denitrification using elemental sulfur

Abstract Experimental studies were conducted to determine the feasibility of autotrophic denitrification with Thiobacillus denitrificans as a nitrate removal process for wastewater. S0-acclimated activated sludge, which can carry out autotrophic denitrification using S0 as electron donors, was prepared by the fill and draw cultivation method. The kinetic constants for the S0-denitrification reaction using S0-acclimated activated sludge under NO3-N limiting growth conditions were determined to be Y = 0.33 mg-NO3-N and b = 0.058 d−1. High percentages of denitrification (over 95%) and rates of denitrification ranging from 0.19 to 0.24 mg-NO3-N/mg-TOC·d were obtained in the continuous denitrification experiments using S0-acclimated activated sludge.

Feasibility of methanolic waste treatment in UASB reactors

Feasibility of methanolic waste treatment in an upflow anaerobic sludge blanket (UASB) reactor operating continuously for a period of more than 400 days was examined. Optimum pH was found to be between 7.0–7.3. In this pH range, there was no excessive build-up of volatile fatty acids and no upset or reactor failure was observed. Elementary pathways of degradation of methanol to methane were shown to be governed by the operating pH. Permissible volumetric loading rate to achieve 80% of TOC removal efficiency was determined to be 8 g-TOC/1·d. Below this value, the effect of hydraulic retention time or loading rate on TOC removal efficiency was not pronounced. Kinetic coefficients of k, Ks, Y and b were determined to be 1.11 g-TOC/g-VSS·d, 0.385 g-TOC/1, 0.213 g-VSS/g-TOC and 0.005 d−1, respectively. Maximum specific methanogenic activity was experimentally found to be 2 g-CH4-COD/g-VSS·d while maximum specific loading rate to achieve 80% of TOC removal efficiency was determined to be 2 g-TOC/g-VSS·d. The results of this study suggest that single-step anaerobic treatment of methanolic waste is highly feasible provided that the pH is maintained close to 7.0.

Treatment performance and microbial structure of a granular consortium handling methanolic waste

Abstract Granular sludge cultivated on brewery waste was subjected to the treatment of methanolic waste in an UASB reactor at mesophilic temperatures. More than 80% of methanol could be converted at an average volumetric loading rate of 15 g methanol/l · d. A maximum volumetric loading rate of 32 g methanol/l · d was applied with conversion efficiency of 70%. The granules were stable after 120 d of operational period although they underwent certain changes. The conversion of methanol has been shown to occur through the intermediate formation of volatile fatty acids which is indicated to be the rate-limiting step. After the substrate shift, there was alteration in the methanogenic population. The scanning electron microscopy of the interior of the granules revealed that the granules consisted of heterogeneous population in the core and the exterior layer but a single morphology in the layer in between. The treatment results manifest good potential of applicability of anaerobic treatment to methanolic wastes.

Nitrification of NH4-N polluted sea water by immobilized acclimated marine nitrifying sludge (AMNS)

Abstract Acclimated marine nitrifying sludge (AMNS) prepared from activated sludge obtained from a night soil treatment plant equipped with a sea water dilution system for controlling the reactors temperature was successfully immobilized using a polyvinyl alcohol (PVA) freezing method. About 2 weeks of recovery culture was required before continuous treatment could be carried out. Transmittance electron microscopic observations of sliced immobilized AMNS pellets indicated that bacteria with an intracytoplasmic membrane dominated the AMNS colony. Continuous nitrification experiments of NH4-N containing synthetic sea water were carried out in a 1.2 l bioreactor containing 57.2 g (wet weight) of immobilized AMNS pellets. The NH4-N removal rate reached a saturation level above an NH4-N loading rate of 1.5 mg-NH4-N/g-pellet/d. The maximum allowable NH4-N loading rate necessary to obtain 90% NH4-N removal was found to be 1.0 mg-NH4-N/g-pellet/d. It was possible to store the immobilized AMNS pellets in a refrigerator for at least 1 week without loss of nitrifying capability. Inorganic carbon source was shown to be a limiting factor in the continuous nitrification experiments. The maximum allowable NH4-N loading rate needed to obtain 90% NH4-N removal increased to 2.0 mg-NH4-N/g-pellet/d through supplementation of an inorganic carbon (IC) source to the influent synthetic sea water.

Fractionation and characterization of brown colored components in heat treatment liquor of waste sludge

Abstract To characterize the colored components in the heat treatment liquor of waste sludge, three distinct liquor samples were fractionated into four fractions (I–IV) by HCl-precipitation and with XAD-7 resin. In all the samples tested fractions III, which were acid-soluble and eluted from the resin with methanol, contained 55–77% of the total color. In one sample fraction I, which was acid-insoluble, also had relatively high color content (22% of the total). Therefore, we defined fractions III and I as main color fractions of the heat treatment liquor. The color of fraction I decreased, but that of fraction III did not decrease during incubation of the liquor with activated sludge. Furthermore, the color of fraction I decreased as that of fraction III increased during the incubation. It was suggested that the colored components in fraction I are converted into the colored components fractionated into fraction III through the biological treatment. Molecular shape of the colored components in fractions I and III were affected by ionic strength: their molecular weight fell in higher ionic strength solvent. The two colored components were degraded with alkaline hydrogen peroxide. Identification of their degradation products revealed that both of them had partially the same chemical structures as the melanoidin pigment synthesized from glucose and glycine, and they had considerable common structures regardless of their presence in different fractions I and III.

Nitrogen pollution of leachate at a sea-based solid waste disposal site and its nitrification treatment by immobilized acclimated nitrifying sludge

Abstract It was found that changes in the nitrogen concentration of leachate from the Osaka North Port sea based disposal site were closely related to the way in which dumping was carried out. The nitrogen concentration of the leachate was low due to the low nitrogen content and slow nitrogen dissolution rate of materials dumped previously in the landfill. The dumping of incinerator ash, noncombustible garbage, waterworks sludge and incinerated ash from sewage sludge were followed, and it was found that they caused a sharp increase in nitrogen concentration in the leachate. The main nitrogen form of leachate was NH 4 -N, and its concentration reached 50 mg/ l after 6 years of landfilling. Successful nitrification treatment of leachate (more than 80% nitrification) was possible by using polyvinyl alcohol immobilized acclimated marine nitrifying sludge with an NH 4 -N loading rate of 2.9 mg-NH 4 -N/g-pellets/d. Low NO 2 -N was detected throughout the continuous nitrification experiments, so the rate limiting step in the nitrification treatment was revealed to be a nitrification step (NH 4 + →NO 2 − ). The addition of inorganic carbon to the test leachate enabled us to perform nitrification treatment even with a high NH 4 -N loading rate. Dolomite limestone was shown experimentally to be able to replace inorganic chemicals.

Preparation of marine nitrifying sludge

Activated sludge taken from night soil treatment plants which employ a sea-water dilation system to decrease the temperature elevation caused by fermentative heat during operation was proved to be a good seed source for the preparation of acclimated marine nitrifying sludge (AMNS). The preparation of AMNS with high nitrifying activity was successful from seed activated sludge obtained from a night soil treatment plant which uses a sea-water dilution system throughout the year, within only a two-month acclimatizing period, by applying the fill and draw cultivation method. The nitrifying activity of our newly prepared AMNS was 13.1 mg-NH4-N/g-MLSS/h, which is comparable to that of fresh water nitrifying sludge. The AMNS was composed of 50 to 100 μm bacterial flocs and showed an excellent settling property. The AMNS exhibited high nitrifying activity, even at a low sodium concentration, but its activity decreased at sodium concentrations above 10g/l. The optimum pH for nitrification by the AMNS was 8.5 and its nitrifying activity did not greatly change within the pH range of 7.0 to 9.0. The optimum temperature for nitrification by the AMNS was 35°C. The nitrifying reaction of the AMNS was proved to be less sensitive to temperature change.

Indices of drinking water concerned with taste and health

Abstract Using the results of a sensory test of drinking water and some findings from the literature, we examined the requisites for tasty and healthy water. It was found that calcium, potassium and silica were correlated to the good taste of water and sulfate and magnesium were factors making water unsavory. We also found that the concentration difference between calcium and sodium was closely correlated to the death rate due to apoplexy and, consequently, the span of life in Japan. From these findings, we derived two equations for indicators of tasty water and healthy water. They were named the O index and K index, respectively, and were expressed as follows; O index = Ca+K+SiO 2 Mg+SO 4 (mg/l) K index = Ca−0.87 Na (mg/l) It has become apparent that tasty water was an O index of over 2.0 and healthy water was a K index of over 5.2. O and K indices were estimated Japanese waters, including representative drinking water, 218 river waters, and famour river waters selected by the Environmental Agency, and these waters were classified as tasty and/or healthy according to the results. This classification seems to be rational because the findings are consistent with everyday experience.

Stoichiometry of activated sludge process for the treatment of synthetic organic wastewater

Abstract For the establishment of a more general and comprehensive activated sludge stoichiometry, which can be applied to the treatment of complex organic wastewater, experimental studies of activated sludge process were carried out. Changes in the elemental composition of activated sludge with the change of sludge retention time (SRT) were investigated. Elemental composition of activated sludge treating synthetic organic wastewater composed of peptone and yeast extract was constant at C5H9NO3 over a wide range of process operating conditions. A definite elemental composition of activated sludge including phosphorus cannot be successfully obtained because of the variations of phosphorus content. Average chemical compositions of activated sludge which was cultured below SRT of 3 d and above SRT of 5 d were C60H114N13O40P2 and C60H113N13O37P, respectively. Yield coefficient (Y) and decay constant (b) were experimentally determined to be 1.22 g-MLSS/g-TOC and 0.126 1/d, respectively. Using the experimentally determined kinetic constants, stoichiometric equation for the treatment of complex organic synthetic wastewater can be successfully developed.