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Ebara Engineering Review No.199

Turbomachinery Blade Optimization by 3-Dimensional Inverse Design Method - 5th Report, Design of High Suction Performance Pumps -

by Kosuke ASHIHARA, & Akira GOTO

Optimization of an inducer pump by the 3-Dimensional inverse method is introduced by designing high suction performance pumps as an example. Experimental validation indicated that a desired high suction performance, under fixed operational conditions, can be maintained by suppressing the inlet backflow, using the fore-loading distribution for the blade loading parameter in the inverse design with zero blade loading at the leading edge. It was confirmed that there was also a suppressing effect on rotating cavitation, a phenomenon which can cause inducer vibration and damages. Also discussed in regard to the main impeller combined with the inducer are the importance of considering the inlet pre-swirl by the inverse design method and the improvement in the suction performance by the inverse designed splitter blade.

Keywords
3-dimensional inverse design, CFD (Computational Fluid Dynamics), Inducer, Pump, Optimum design, Blade loading, Rotating cavitation, Splitter blade

A Study on the Application of Ozonation for Excess Sludge Reduction in Sewage and Food Processing Wastewater Treament

by Takuya KOBAYASHI, Kiyomi ARAKAWA, Yousei KATSU, & Toshihiro TANAKA

A study was made on ozonation for reducing excess sludge in sewage and food processing wastewater. Ozonation applied for sewage treatment which used a settling tank revealed that an injection of 1 kg of ozone resulted in approximately 3 kg of sludge reduction. A biological reaction was also confirmed inside the ozone reactor. Membrane filtration used for solid-liquid separation resulted in less sludge reduction than in the case of using the settling tank. However, studying the sludge generation for both cases revealed a clear reduction in microorganisms, i.e. for both the settling tank and membrane filtration. In contrast, ash elements and organics other than microorganisms were hard to become reduced by membrane filtration, thus resulting in lower sludge reduction.

Keywords
Ozonation, Sludge reduction, Sludge liquefaction, Membrane bioreactor, Sewage & food processing wastewater

Development of a Vacuum Deaerating Machine for Sewage Sludge

by Ryosuke HATA, Takao HAGINO, Yoshiharu IRIUCHIJIMA, & Hideaki YOSHIDA

A vacuum deaerating machine was developed and tested at a centralized sludge treatment facility of a sewage treatment plant to study treatment effects on sewage sludge which contained gases due to putrefaction occurring during a long-distance transportation. Basic experiments indicated that there was an improvement in settled thickening in the gravity thickener. Further tests were carried out during four seasons using a pilot plant. Test results indicated that vacuum deaeration worked to completely inhibit the production of scum in the gravity thickener throughout the year. The recovery of suspended solids during Summer and Autumn months was 20% higher than that by an agitation deaeration system. A pilot plant scale test was also conducted to study the effects of vacuum deaeration on sludge dewaterability. The moisture content in vacuum aerated sludge cakes was less, 1.9% for Autumn and 1.8% Winter, than that in non-vacuum-aerated sludge cakes. Results of tests on sludge odor indicated that there was less odor due to a forced removal of gases by vacuum deaeration.

Keywords
Vacuum deaeration treatment, Centralized sludge treatment, Gravity thickener, Scum, Suspended solids recovery, Settled thickenability, Sludge dewaterability, Hydrogen sulfide, Sludge odor

Improvement in the Water Recovery and Scale Prevention of an RO System

by Takayuki SAITOH, & Takuhisa HANDA

An improvement in the water recovery and scale prevention was achieved for an RO system. The mechanism of scale-forming in brine was revealed by studying the coagulation characteristics of hydroxides (in hardness elements) and silica, both of which were believed to be probable causes of scale-forming. It was established from this that scaling was most likely to become formed when the pH level of the brine was in the proximity of neutral. In particular, Mg ions were found to react with ions and form magnesium silicate. A method was worked out to prevent scale-forming and the water recovery efficiency of an RO system was thus improved.

Keywords
Reverse osmosis, Pure water, Water recovery, Brine, Silica, Hardness, Scale, Coagulation

Wet Electrolytic Reaction Under Subcritical Water Conditions

by Roberto Massahiro SERIKAWA

A study on the electrolytic reaction of an aqueous electrolyte solution revealed that such reaction under a subcritical water condition was totally different from that at room conditions. Under the condition of 250 deg. C and 7 MPa, there was no occurrence of the typical electrolysis which produces hydrogen and oxygen. However, the electrolytic reaction under this subcritical reaction was found to effectively mineralize compounds, such as that of ammonia, and the majority of other organics in wastewater. This electrolytic reaction was further improved by adding oxygen from an external source which resulted in an oxidation current efficiency exceeding 100%. The following describes a continuous wastewater treatment process and apparatus based on this reaction.

Keywords
Elecrolytic reaction, Subcritical water condition, Wet Oxidation, Wastewater treatment, High current efficiency, Novel electrolytic reaction, Continuous reactor, Three dimentional electrodes

ICP Multi-beam Etching Technology for Minimizing Damage

by Katsunori ICHIKI, Keisuke SAKAMOTO, & Seiji SAMUKAWA

A novel ICP Multi-beam Etching system is currently under development for use in ULSI manufacturing. This system features high performance, low-energy, neutral beam etching and minimizes radiation damage by charge buildups and ultraviolet photons. The beam source consists of an inductively coupled plasma (ICP) source and top/bottom plate electrodes. The bottom plate electrode has apertures (1 mm in diameter and 10 mm long) for extracting neutral beams from the plasma. Applying a DC bias to the top/bottom plate electrodes causes generated ions (both positive and negative) to become accelerated towards the bottom electrode, where they become converted into neutral atoms and irradiated to the substrate. Negative ions were found to become more efficiently converted into neutral atoms (almost 100%) than positive ones. The maximum flux density was equivalent to 4 mA/cm2.

Keywords
Neutral beam, Etching, Inductively coupled plasma, Damage-free, Charge buildup, Ultraviolet, Negative ion, Pulse-time-modulation, Calorimeter, Neutralization efficiency

Energy Recovery Type Sludge Retreatment Center - Kainan Kaisou Environmental Associate -

by Shinji YOSHIDA

EBARA's energy recovery type, UF Denipac system, is being used for night soil treatment by Kainan Kaisou Environmental Associate, Wakayama Prefecture, Japan. This system features membrane filtration and high load nitrogen removal. The treatment capacity is 89 kl/day of night soil, 41 kl/day of septic tank sludge, a total of 130 kl/day. The compositor is capable of treating 0.25 t/day of garbage and 0.25 t/day of dried sludge. The system is also equipped with a photovoltaic power generator (20 kW) and a heat recovery system for recovering heat from the biological reactor and making use of this heat in an adjacent greenhouse. Such effective use of heat recovered from biological treatment is a rare practice.

Keywords
Heat recovery, UF-Denipac process, Compositor, Photovoltaic power generator, Biological reactor, Greenhouse

Large-scale MSW Incinerators and Plasma Ash Melting Systems for Waste Incineration Plants

by Hajime JIMBO, Makoto SASAKI, Yoji SATO, Teruaki TSUKAMOTO, Yoshinobu URAKAMI, Takehiro OKA, & Yukio NOGUCHI

EBARA's large-scale MSW incinerator (capacity: 700 t/day) and a plasma ash melting system are been installed at Tokyo's Adachi Incineration Plant, as an addition to another large-scale MSW incinerator which is already being operated with favorable feedback. Another large-scale MSW incinerator (capacity: 600 t/day) is scheduled to be installed in a waste incineration plant in Keelung, Taiwan. One feature of this equipment is that a scrap and build method is being used in the construction, thus enabling the plants to be functional during construction. Various data, including those on the prevention of dioxins and other pollutants, as well as operational data, have been obtained in regard to large-scale MSW incinerators. The following introduces the equipment and discusses such data.

Keywords
MSW incinerator, Plasma-ash melting system, Scrap and build