The Fibria Pulp and Paper Mill in Jacarei is increasing ozone production to 750 kg/h or 18 tons per day. This is one of the largest ozone installations in the world. Bleaching pulp with ozone is more environmentally friendly than alternative bleaching systems. Ozone is also a very powerful and effective bleaching agent.
Ozone is a very powerful oxidizing agent and the biggest challenge in using it to bleach wood pulp is to get sufficient selectivity so that the desirable cellulose is not degraded. Ozone reacts with the carbon carbon double bonds in lignin, including those within aromatic rings. In the 1990s ozone was touted as good reagent to allow pulp to be bleached without any chlorine-containing chemicals (totally chlorine-free, TCF). The emphasis has changed and ozone is seen as an adjunct to chlorine dioxide in bleaching sequences not using any elemental chlorine (elemental chlorine-free, ECF). Over twenty-five pulp mills worldwide have installed equipment to generate and use ozone.
The ozone system budget for teh Fibria mill is valued at $9,200,000 dollars. The mill has a production capacity of 1.1 million tons of bleached pulp. The additional ozone will allow the plant to increase pulp output by 15%. The mill processes 3,600 tons per day of eucalyptus pulp which feed two separate prdiction lines.
Ozone use spans a wide range of applications, pulp bleaching being one where very large scale generators are used.
New upgrades to the Martin’s Ferry water treatment plant included ozone generators that remove iron and manganese before the water is sent to a distribution pump. The ozone generators were installed about one year ago. The plant has the capacity to produce five million gallons of water daily.
Ozone is widely used to remove iron and manganese from drinking water. Since ozone can be made from air, it does not require the purchase or storage of dangerous chemicals. In addition, ozone is less likely to add undesirable byproducst to the water as some other chemicals might. Ozone generally reverts to oxygen in teh water. There are also situations when more conventional chemicals might not work given the pH of the water or other compounds in the water that might be bound up with the iron making it difficult to remove.
In general, the transferred dose of ozone required is about 0.5 mg of ozone per mg of iron, or 0.9 mg of ozone per mg of mangananese. These doses are relatively small versus other applications of ozone for use such as disinfection. So, ozone can be an economical alternative.
In previous posts we have talked about reuse of wastewater for drinking purposes including the feelings of Americans towards the use of wastewater for their water supply. In reality, many American’s already use wastewater as their drinking water source. If your drinking water plant is down stream of another cities wastewater plant, you are in effect drinking their wastewater. This does not include the impact of farm run off and run off from animal waste. The standards for treating water downstream of the wastewater plant is not nearly as high as for direct reuse, but that is what is happening ecluding teh dilution effect.
One aspect of the issue of water reuse that we have not covered is the anlytical aspects for evaluating water quality in these situations. Obviously, utilities must be aware of the different contaminants present in the water and have clearly defined public health goals before deploying technologies to treat the water. Some of the contaminants associated with pharmaceutical or personal care producsts are in extrmely low concnetrations, e.g. nano gram per liter quantities. So, sophisticated analytical techniques are required to measure these contaminants before and after treatment. Additional analytical techniques are required for measuring the advanced oxidants that are sometimes applied in these applications.
In terms of treatment, the complexity of the chemistry of water contaminants at different stages of the water cycle results in no single technology being able to remove all the contaminants. Thus, a multiple barrier system is needed to ensure their reduction and removal. This is the same approach promoted by the US EPA to balance treatment of difficult to remove micro organisms while minimizing disinfection by products.
Advanced oxidation technologies effectively remove many pharmaceutical and personal care products and disinfect the water. Ultraviolet (UV) light can be effective in destroying some contaminants, such as N-nitrosodimethylamine, as well as killing a most micro organisms. Reverse osmosis can remove most contaminants, but creates a concentrated waste stream that contains the contaminants. Ozone, another strong oxidant, can also be used before or after water enters the reverse-osmosis membranes to remove contaminants.
Water reuse treatment often includes the use of UV or oxidation and membrane-based technologies as part of a multibarrier treatment scheme. Alternative schemes such as ozone and granular activated carbon filters are being explored to disinfect the water and remove contaminants, residual odours, discolouration and by-products created by other treatment processes.
Water reuse is slowly becoming a reality in the US out of necessity due to decling water source quality and increasingly stringent regulations. Ozone and advanced oxidation have an important role to play in this regard along with other advanced water treatment technlogies.
Most Americans have limited knowledge about their drinking water supply,but they are concerned about it, and believe recycling water is something that should be considered according to a recent survey. However, Americans are less accepting of drinking recycled wastewater in a practice known as toilet-to-tap, the survey found.
With clean water growing scarce in much of the world, and with shortages possible in 36 U.S. states in the next year, according to the General Accountability Office, the survey found 66 percent of Americans feel positive about water re-use. Eighty-three percent of Americans surveyed said they were concerned about the availability of clean water in the future. The online survey of 3,000 people in the United States, Singapore and China showed Americans’ understanding of water issues lags behind those surveyed in the other two countries.
Wen Americans were asked about having wastewater recycled into drinking water – only 30 percent supported this – though 51 percent were in favor of swimming in recycled water and 51 percent agreed that it was drinkable. However, eight out of 10 Americans favor using recycled water for other uses, including power generation, landscaping, industrial processing and manufacturing, toilet-flushing, car washing and agricultural irrigation.
While Americans generally feel water is the single most important service they receive, beating out electricity and heat, 31 percent don’t know where their water comes from, compared with about one in 10 in China and Singapore.
Advanced water treatment technologies such as ozone, UV and some membrane processes can convert various wastewater source to drinking water quality. Education of the public on the efficacy of these technology for producing safe water from even sewage is necessary. As noted on earlier posts some water recycling plants are providing this education.