19-04-2013, 04:24 PM
OZONE BASED WASTE WATER TREATMENT SOLUTIONS
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Abstract
Ozone has been used in wastewater treatment for decades as a form of tertiary sterilization. As a tertiary
treatment process it is generally thought to be too expensive to produce, and very wasteful. Ozone is a
strong oxidant and will react with unsaturated hydrocarbons very effectively. Ozone, combined with Seair`s
patented diffusion technology can do much more.
Ozone combined with microbubble diffusion allows for extremely high mass transfer of the gas to
wastewater. This means creating a supersaturate solution of ozone with little to no off gassing in a very
stable state. Supersaturate ozone solutions allow reactions with unsaturated hydrocarbons to happen faster,
but also push reactions that typically would not happen in less concentrated solutions. BOD, COD, TSS and
bacteria are now easily eliminated very efficiently and economically, as a result there is no primary or
secondary sludge formation
The key to Seair’s systems is the ability to efficiently diffuse ozone and oxygen gas into the wastewater
stream. Seair’s diffusion system produces 5 micron sized bubbles through the Seair’s patented diffusion
chamber. The micro-bubbles dramatically increase the available surface area for reaction and result in an
extremely stable super-saturate solution. Gas remains in solution for extended periods of time, which
facilitates maximum treatment results and minimal off gassing.
Introduction
Optimal wastewater treatment is a challenge facing many municipalities and organizations throughout the
world. However, there are some economically viable options for environmentally conscious businesses and
governments.
The use of ozone coupled with biological treatment can be a very cost-effective and efficient wastewater
treatment solution (Marco et al, 1997). Ozone has a very strong oxidation potential (Beltrán, 2004) which
makes it ideal in wastewater treatment applications. When combined with conventional biological treatment
methods, a cost effective and proficient wastewater treatment system is achievable. The focus of this study
is the evaluation of the effectiveness of an advanced diffusion system’s ability to use ozone and oxygen in
the treatment of wastewater.
Holding/Equalization Tank
The first process unit in the WWTP is a holding/equalization tank. The function of the unit is to provide
sufficient retention of raw wastewater influent to allow the operation of the subsequent process units in a
batch mode. Raw wastewater is pumped to the holding/equalization tank from an external lift station. The
tank functions solely as a storage/equalization tank. Fluid in this tank is not mixed or aerated and therefore is
in an anoxic state. No treatment processes occur inside the equalization tank; it is necessary due to the
diurnal nature of industrial camps (Marsh, 2007).
Primary Ozone Treatment Tank (Pre-treatment)
The next process unit is the primary advanced oxidation system using ozone. The primary purpose of this
treatment process unit is to chemically oxidize the easily oxidized biochemical oxygen demand (BOD) and oil
and grease (O/G). Within the first treatment step a grinder pump grinds the sewage to increase the surface
area for ozone treatment (Marsh, 2007).
The primary ozone treatment tank operates as a batch reactor. The fluid in the tank is continuously circulated
through a patented SA75 Seair ozone diffusion system at a hydraulic rate of 140L/min. Ozone is generated
on-site using oxygen-enriched air, which is delivered by an AS12 oxygen generator. The ozone generator is
supplied by Guardian Manufacturing Inc. and is capable of producing up to 8% (32g/hr) ozone by weight in
the gas stream when using pure oxygen. Dissolved ozone levels in this tank are maintained at about 2mg/L
(Marsh, 2007).
Aeration Tank
The aeration tank in the WWTP provides some aerobic biological treatment of the ozone-pretreated
wastewater. Microbes utilize the organic matter in the wastewater as a food/energy source, producing
additional biomass, carbon dioxide and water. The process does not include biomass collection and
recycling. Biomass accumulation occurs as a result of only a portion (i.e. 37%) of the tank’s contents being
removed each cycle, and therefore a certain level of suspended growth biological treatment develops
(Marsh, 2007).
The aeration tank is operated as a batch reactor. The wastewater in this tank is continuously circulated
through a patented SA75 Seair diffusion system at a hydraulic rate of 100L/min. The Seair diffusion system
is supplied with oxygen-enriched air by an AS12 oxygen generator, which results in elevated dissolved
oxygen (DO) levels in the tank (Marsh, 2007).
Plant Hydraulics
The entire WWTP discharge and transfer is controlled through the high level float in the equalization tank.
When the high level float triggers, the ozone-polishing tank discharges and is refilled from the fluid in the
aeration tank. The primary ozone treatment tank then discharges to the aeration tank and the
equalization/holding tank discharges to the primary ozone treatment tank. The overall average design
hydraulic retention time in the WWTP is 18.6 hours and in the three treatment process units is 14.6 hours.
(Marsh, 2007)
Results
The Seair PWW40 was monitored and sampled over the course of normal operations at the Seair Septic
Inc. facility in Spruce Grove, Alberta, Canada from Monday, April 23 until Friday, April 27, 2007. The influent
used in the trials was composed of raw wastewater from operating plants used in work camps. The raw
sewage was drawn from wet sleeping units as well as a kitchen and common area, providing a typical
sewage loading influent.