Norihito Tambo

Physical characteristics of flocs—I. The floc density function and aluminium floc

Abstract Some characteristics of floc density were illuminated by experiments and model floc simulation by using clay-aluminium flocs. As an aluminium floc is a very fragile particle, the authors adopted an experimental method in which the settling velocity and diameter of a discrete floc were measured in a quiescent water column. Floc density was calculated by introducing the measured values and some constants such as water density and viscosity into a suitable settling velocity equation. In this study a modified Stokes equation was used. From the experimental results, the following conclusions were obtained. 1. (1) Floc density decreases as floc size increases, and the floc diameter and the floc effective density (buoyant density = floc density — water density) have a straight line relationship on a logarithmic paper. This line is characterized by two constants, K p and a , which show the slope of the line and the floc effective density of 1 cm diameter floc. The authors have designated this relationship as the floc density function. 2. (2) ALT ratio (aluminium ion concentration dosed/suspended particle concentration) greatly affects the clay-aluminium floc density. As ALT ratio decreases, the floc density at the fixed size increases. Other effects of coagulation condition upon floc density function were also discussed. 3. (3) The floc density function of coagulated colored water was studied. Iron, magnesium and calcium flocs with clay were also studied for reference purposes. 4. (4) The floc density function was verified by the model floc simulation. Model flocs were produced by computer and the floc density function was derived by substituting the number of the primary particles contained in a floc and the model floc diameter into a mass balance equation of a floc particle.

Physical characteristics of flocs—II. Strength of floc

Characteristic features of floc strength were examined by theoretical and experimental studies by using clay-aluminium flocs. From the studies, the following conclusions were obtained. 1. (1) Maximum floc diameter dmax under an agitation intensity is evaluated by the following equations: where, ϵ0: the effective rate of energy dissipation [erg cm−3·s], Kp: the exponent of the floc density function [−], λ0: micro scale of the isotropic turbulence [cm], dmax: the maximum diameter of flocs [cm], K,K∗: constants. In practice, however, the latter equation is possibly used. 2. (2) From the above equation in viscous subrange, and Kp-value of the floc density function evaluated in the previous paper, dmax will be changed with the rate of energy dissipation ϵo or the rate of the agitation blades rotation Nr as the following equation: 3. (3) Relative floc binding strength can be evaluated by the following equation: where, σ: the floc binding strength, a: coefficient of the floc density function, d: diameter under an agitation intensity, Suffixes 1 and 2 denote the characteristic values of flocs 1 and 2, respectively. 4. (4) After the theory and experimental studies, characteristic features of clay-aluminium flocs were evaluated.

Physical aspect of flocculation process—I: Fundamental treatise

Abstract A dimensionless equation for the floc growth operation was developed and simulation of the floc growth operation was carried out to obtain the numerical solutions of the floc growth equation. A comparison of the simulation results with the experimental results suggested that it was necessary to introduce a collision-agglomeration function into the original floc growth equation. The floc growth equation with the collision-agglomeration function gave simulation results which almost coincided with the experimental results. The self-preserving nature of floc size distribution was found by using the results of both simulation and experiment. The results of simulation and experiment were shown in the normalized floc size distribution and the normalized removal rate in an ideal sedimentation basin.

Treatability evaluation of general organic matter. Matrix conception and its application for a regional water and waste water system

Abstract For the evaluation of the behaviors of general organic compounds in a regional water and waste water system and individual or combined water treatment processes, the authors have proposed to use some water quality indices in connection with scale grouping of organic compounds. The treatability of various types of treatment processes such as biological treatment, chemical coagulation and carbon adsorption were well evaluated with three comprehensive water quality indices such as TOC. TOC/E260 (absorbance at 260 nm) and E220 (absorbance at 220 nm) connected with the gel-chromatographic grouping after a water quality matrix conception.

Physical aspect of flocculation process—II. Contact flocculation

Abstract Kinetic equations which describe the process of contact flocculation in solids contact clarifiers were proposed. Decrease of micro-flocs with the contact of high concentration and large diameter well-grown-flocs both in a turbulent flocculation chamber and in a floc blanket of upflow clarifier were discussed. First order equations with the micro-floc concentration were derived theoretically for both types of contact flocculation. By experiments, these kinetic equations were verified and their coefficients were evaluated. Finally, practical equations for the design of micro-floc removal process with the contact of well-grown-flocs both in a turbulent flocculator and in a floc blanket were proposed.

An anaerobic fluidized pellet bed bioreactor process for simultaneous removal of Organic, nitrogenous and phosphorus substances

Abstract A new wastewater treatment process, which is named herein “the anaerobic fluidized pellet bed (AFPB) bioreactor process”, is developed for simultaneous removal of suspended solids, organic matter, phosphorus and nitrogen. This process is composed of two stages: an upflow AFPB bioreactor for the first stage and an activated sludge aeration tank with a sludge settling zone for the second stage. The first stage, the AFPB bioreactor, is introduced as an alternative to the primary clarifier. In this stage, polymerized aluminum chloride and a weak anionic polymer are dosed in order to coagulate suspended solids, colloidal matters and phosphorus and to generate sludge pellets that are large enough to settle rapidly. The excess sludge pellets are withdrawn from the bottom of the AFPB bioreactor. The second stage is primarily designed for the usual aerobic biological treatment of organic matter. In addition, as the aeration tank is operated at solid retention times long enough to ensure the growth of nitrifiers even at temperatures below 10°C, high nitrification is achieved in the second stage. The nitrified effluent is recycled from the second stage to the AFPB bioreactor, and denitrification completely accomplished under the anaerobic conditions. The organic matter necessary for the denitrification is supplied through anaerobic biological hydrolysis of the sludge pellets in the AFPB bioreactor. With a total retention time of 4 h (2 h in the AFPB bioreactor and 2 h in the aeration tank) and a recirculation ratio of 300% based on the influent flow rate, the average removal efficiencies of suspended solids, total COD and total nitrogen are found to be 99, 95 and 75%, respectively. Total phosphorus was below the detectable level in most cases.

Optimization of Flocculation in Connection with Various Solid-Liquid Separation Processes

Coagulation and flocculation always involve solid-liquid separation processes. Numerous studies on coagulation and flocculation for water and wastewater treatment have postulated sedimentation and/or filtration as the typical accompanying separation processes. Therefore, much data is available on optimal coagulation and flocculation conditions defined on the basis of the above stream. Very often “good floe” was defined according to a conventional jar test procedure or similar procedures for optimal design and operation of treatment systems. In recent years, various new solid-liquid separation processes have been introduced into water and wastewater treatment streams. Direct sand filtration, coarse media filtration, multiple media filtration, microfiltration, ultrafiltration, fluidized pellet bed separation, etc. are relatively new or very recent technical innovations which broaden the range of possibilities for optimizing coagulation and flocculation. In the following discussion, the author intends to present a blueprint for selecting an effective solid-liquid separation process, and to propose optimal coagulation and flocculation conditions based on some of his own work.

Dual Wave Length Photometric Dispersion Analysis for the Dynamic Monitoring of Coagulation Process

凝集機構の解明やモデル化に際して, 凝集の進行過程を的確に把握することが肝要である。本稿では, 凝集過程にある複数の成分を含む試料液の流れに波長の異なる光を同時に照射して, 各凝集成分に特有なもしくは支配的な吸収や散乱を生じさせる波長の透過光量を同時計測し凝集剤を含む複数成分の凝集の進行状態を経時的に解析することを試みた。2波長の吸光度の平均値, 変動成分の標準偏差, 相関係数より, 水中成分を長波長に散乱を示す懸濁性成分, 短波長にのみ吸収・散乱を示す懸濁性成分 (不溶化水酸化アルミニウム等), 短波長に吸収を示す溶解性成分 (水酸化アルミニウムコロイド等) の3成分に分けて, 各々の濃度を紫外部の吸光度として推算する方法を提案した。提案された計測理論に基づいて製作された機器を用いて, 粗懸濁質 (Sephadex粒子) がアルミニウム水酸化物によりSweep型で凝集される過程を実測例として取り上げ, 計測方式の有効性を説明した。

PERFORMANCE OF FINNED CHANNEL SEPARATOR

ABSTRACT Conventional sedimentation basins are designed to utilize only gravity acting on flocs as the driving force of separation, and to separate flocs in static flow conditions. The extreme designs of conventional settling basins are slant-pipes (U.S. practice) and multi-stage slant-boards (Japanese practice) tanks which have the lowest overflow rate with laminar flow regime. The authors succeeded to overcome the limit of the overflow rate improvement and to attain a much higher efficiency of floc separation by placing fins on the slant-boards in the upright position to the rectangular direction of flow and admitting flocs into numerous wake vortex streams behind the fins for dynamic separation. In the study, high efficiency of the new dynamic separation method was proved by experimental and practical plant studies. Flow pattern of the finned channel was identified by using a flow visualization technic of hydrogen bubbles (electrolysis of water). After the flow pattern and model experiments of floc removal, a mathematical model to explain the high performance was proposed and its numerical constants were evaluated. Through the study it became possible to calculate the performance of the finned channel separator for theoretical design.