Bench-scale evaluation of the activated sludge process for treatment of a high -strength chemical plant wastewater

A bench-scale treatability study was conducted on a high-strength wastewater from a chemical plant to develop an alternative for the existing waste stabilization pond treatment system. The objective of this study was to determine the treatability of the wastewater by the activated sludge process and, if treatable, to determine appropriate operating conditions, and to evaluate the degradability of bis(2-chloroethyl)ether (Chlorex) and benzene in the activated sludge system. Four 4-L Plexi-glass, complete mixing, continuous flow activated sludge reactors were operated in parallel under different operating conditions over a 6-month period. The operating conditions examined were hydraulic retention time (HRT), sludge retention time (SRT), nutrient supplement, and Chlorex/benzene spikes. Generally the activated sludge system treating high-strength wastewater was stable under large variations of organic loading and operating conditions. At an HRT of 2 days, more than 90% removal efficiency with good sludge settleability was achieved when the organic loading was less than 0.4 g BOD$\sb5$/g MLVSS/d or 0.8 g COD/g MLVSS/d. At least 20 days of SRT was required to maintain steady operation. Phosphorus addition enhanced the performance of the system especially during stressed operation. On the average, removals of benzene and Chlorex were 73-86% and 37-65%, respectively. In addition, the low-strength wastewater was treatable by activated sludge process, showing more than 90% BOD removal at a HRT of 0.5 days. In general, the sludge had poor settling characteristics. The aerated lagoon process treating high-strength wastewater also provided significant organic reduction, but did not produce an acceptable effluent concentration. ^

Hydrogen embrittlement risk of high strength galvanized steel in contact with alkaline media

The critical conditions for hydrogenembrittlement (HE) risk of highstrengthgalvanizedsteel (HSGS) wires and tendons exposed to alkaline concrete pore solutions have been evaluated by means of electrochemical and mechanical testing. There is a relationship between the hydrogenembrittlementrisk in HSGS and the length of hydrogen evolution process in alkalinemedia. The galvanizedsteel suffers anodic dissolution simultaneously to the hydrogen evolution which does not stop until the passivation process is completed. HSGS wires exposed to a very highalkalinemedia have showed HE risk with loss in mechanical properties only if long periods with hydrogen evolution process take place with a simultaneous intensive galvanized coating reduction.

Effects of hydrogen assisted stress corrosion on damage tolerance of a high-strength duplex stainless steel wire for prestressing concrete

The study brings new insights on the hydrogen assisted stress corrosion on damage tolerance of a high-strength duplex stainless steel wire which concerns its potential use as active reinforcement for concrete prestressing. The adopted procedure was to experimentally state the effect of hydrogen on the damage tolerance of cylindrical smooth and precracked wire specimens exposed to stress corrosion cracking using the aggressive medium of the standard test developed by FIP (International Prestressing Federation). Stress corrosion testing, mechanical fracture tests and scanning electron microscopy analysis allowed the damage assessment, and explain the synergy between mechanical loading and environment action on the failure sequence of the wire. In presence of previous damage, hydrogen affects the wire behavior in a qualitative sense, consistently to the fracture anisotropy attributable to cold drawing, but it does not produce quantitative changes since the steel fully preserves its damage tolerance.

Biological treatment of high strength petrochemical wastewater /

Mode of access: Internet.

Causes and control of cracking in concrete reinforced with high-strength steel bars : a review of research /

Mode of access: Internet.

Optimized sections for high-strength concrete bridge girders : effect of deck concrete strength.

"HRDI-06/10-06(750)E"--Back cover.

High strength, high modulus fibers by pyrolysis of polymeric fibers

Mode of access: Internet.

High-strength bolts for bridges /

"Demonstration project no. 88."

Final report on development and fabrication of high strength simulated rocket motor cases by cryogenic stretch forming process. Technical documentary report nr. AFML-TR-64-410.

"MM Project nr. 8-101."

Endurance tests of rolling contact bearings of conventional and high temperature steels under conditions simulating aircraft gas turbine applications

"Propulsion Laboratory, Contract no. AF 33(600)-22860, Task 3066-30233."

Development of low alloy steel compositions suitable for high strength steel castings

Mode of access: Internet.

Research on properties of high strength materials suitable for high temperature applications

"Materials Central, Contract no. AF 33(616)-6552, Project no. 7381."

The evaluation of a high strength experimental grade of poco graphite/

Cover title.

Effects of testing variables on the measured compressive strength of high-strength (90 MPa) concrete /

Mode of access: Internet.

Progress report on slip of structural steel double-lap joints assembled with high-strength bolts. 1st-

Mode of access: Internet.