Ozone and UV Good Choices for Treating Water From Green Roofs

A recent report from the Texas Water Development Board entitled: Effect of Roof Material on Water Quality for Rainwater Harvesting Systems was recently published. As the title mentions, the study centered on the effect that different roof material have on the quality of collected rainwater. A survey of the most common roofing materials in Texas was completed, and found that the three most common were asphalt-fiberglass shingles, Galvalume® metal panels, and concrete tiles. In this post we will look at two specific issues in the study, dissolved organic carbon (DOC) and coliform contamination. The study looked at the impact of the first flush through third flush of water off the surface. As expected, the first flush contains the most contaminants.

Runoff from the green roof was lowest in both Total Coliform and Fecal Coliform compared to the other treatments, but both were present in all treatments after the first flush. Coliform can be eliminated with a UV or ozone disinfection system, but a green roof goes a long way towards eliminating it before filtration.

DOC tests measure the amount of organic material in a solution. Organic materials from plants and animals can break down to such small sizes that they can become dissolved in water. Because DOC is derived from living organisms, it makes sense that the water collected from the green roof had the highest levels of DOC’s.

The big implication here is on the use of chlorine to disinfect collected rain water. Chlorine reacts with DOC to form all sorts of undesirable byproducts such as trihalomethanes and haloacetic acids. To avoid this problem all together, collected rainwater from a green roof should be treated with a disinfectant other than chlorine before use. UV light and ozone are proven alternatives to chlorine.

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Growing Importance for Ozone and UV in Advanced Water Treatment

The urgency caused by the deterioration of traditional water sources have increased interest in advanced water treatment technologies, with increasingly stringent regulations encouraging the use of alternative technologies. Poor water quality, the need to upgrade or replace existing plants, and general aversion to chemical water treatment technologies have made a strong case for novel treatment solutions. Alternatives to chlorine (ozone and UV) have been in the spotlight since the emergence of concerns regarding disinfection by-products (DBPs). In the United States, the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) and the Stage 2 Disinfection By-Products Rule (Stage 2 DBPR) are major drivers for alternative chlorine disinfection technologies such as UV and ozone. The LT2ESWTR is specific to Cryptosporidium, a pathogen present in most surface water. UV is significantly less capital- and operation-intensive than other cryptosporidium inactivation technologies such as ozone and membranes.

Regulations, especially at the Federal level, are one of the key reasons for the success of advanced water treatment technologies in municipalities. UV is expected to be especially popular among municipalities that must meet treatment credits, but lack sufficient funds to retrofit the entire facility. Adverse public opinion about the quality of tap water has impelled governments to focus on safeguarding their water supplies. Widely covered deadly outbreaks of cryptosporidium in American cities have further enhanced citizens’ awareness and intensified the need for sophisticated treatment equipment. Numerous industries such as pharmaceuticals, life sciences, semi conductors, and food & beverages have raised their demand for high-purity water systems. Most of these industries prefer non-chemical based disinfection methods because residual chemicals in process water could affect the manufacturing process.

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Ozone Seen As Best Treatment for Ballast Water

Regional training and workshop on the legal implementation of the ballast water management (BMW) convention was held in Lagos, Nigeria to support the timely and harmonized implementation of ballast water convention in the West and Central Africa region. There has been a growing concern over the problem of invasive alien species in the marine environment as a result of ballast water carried by ships. Ship ballast water serves as a vector for the transfer of alien species and harmful aquatic algae and other pathogenic organisms from one part of the world to the other.

Ballast is the additional weight a ship traveling without cargo or partially laden must take on board to enable it to operate effectively and safely by keeping the ship deep enough in the water to ensure efficient propeller and rudder operation. Shipping, which is essential to the global economy, provides the most effective means of transporting bulk goods over great distances. With some 50,000 merchant ships sailing the world’s oceans, with a combined tonnage of around 600 million gross tonnes, ships carry over 90 percent of all global trade.

Although ballast water is crucial to the safe operation of ships, studies have shown that when ballast water is taken on board the ship, the organisms living in that water are also drawn into the ballast tanks. Depending on duration of voyage and other factors, many of these organisms survive the journey and are subsequently released live into the waters of destination port when the ballast water is discharged.

At the regional training and workshop by the GloBallast Partnership of International Maritime Organisation (IMO) in collaboration with the Interim Guinea Current Commission (IGCC) and the Nigerian Maritime Administration and Safety Agency (NIMASA), which held at the NIMASA Resource Centre at Kirikiri, Lagos, 12 countries from the sub region participated.

In response to these threats, the IMO adopted the international convention for the control sand management of Ships ballast water and sediments, to minimize the transfer of harmful aquatic organisms and pathogens. As part of the international response, the convention on biological diversity came out in 1992. At the IMO, discussions already started in 1973, while preliminary guidelines for BMW developed in 1991 and full guidelines adopted by IMO assembly in 1997. International convention for the control and management of Ship’s Ballast Water and Sediments was adopted 13 February 2004.

Treatment methods include mechanical treatment, mainly by filtration or cyclonic separation; Chemical treatment, addition of ‘active’ or other substances that will render Harmful Aquatic Organisms and Pathogens (HAOP) harmless and Physical treatment which includes Thermal, ultraviolet magnetic and ultrasound devices. It was agreed that the modern and best way of treating ship’s ballast water globally is through ozone disinfectant, to sterilize the water before discharging it back into the ocean. Ozone is a widely used disinfectant for a variety of water treatment applications.

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Oregon Cities to Use Ozone for Drinking Water Treatment

The cities of Tigard and Lake Oswego, OR will use conventional drinking water treatment plus ozone to best meet their future water treatment needs. This is the first phase of planning for an expansion of the city’s water supply through a water partnership with Tigard. Initially 18 different water treatment technologies were examined for social, environmental and economic benefits.

Ozone was recommended because it is capable of addressing emerging concerns about currently unregulated contaminants. It was determined that adding ozone as an additional treatment barrier would best protect public health in the long term. Ozone would pro actively ensure the best taste year round and would reduce the amount of chlorine used for disinfection, among other benefits.

The cities plan on beginning the system upgrades in the 2012-2013 fiscal year.

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Napa Adds Ozone to Drinking Water Plant to Meet Treatment Objectives and Improve Taste

Napa, CA will install advanced ozone treatment in the new water treatment plant in Jamieson Canyon. The plant is undergoing a $35 million upgrade and expansion to handle more water from the State Water Project for city of Napa customers. There is still money in the project’s $3.5 million contingency account to pay for additional ozone injection equipment. More ozone treatment will cost $1 million to $1.5 million. The new equipment will enable the plant to meet future water treatment requirements, while improving the taste of the water, she said.

Ozone is widely used for taste and odor control in drinking water.

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Revised Edition of Reference Text on Chlorine, Ozone and UV has been Published

The water industry has made substantial advancements in its understanding and application of chlorine, ozone and UV for water and wastewater treatment since 1998, when the Fourth Edition of White’s “Handbook of Chlorination and Alternative Disinfectants” was published.

At the request of the Wiley publishing company, Black & Veatch has completed a two-year revision process for the Fifth Edition of the handbook, which was authored and reviewed by leading industry experts to reflect the most current scientific advancements available.

The book balances theory with practice and gives details about technological advances in the use of UV and ozone as disinfectants. It explores alternative disinfectants, such as chlorine dioxide, iodine and bromine-related products and discusses advanced oxidation processes for drinking water and wastewater treatment. Along with new developments in the production and handling of chlorine, the book also examines current regulations governing the use of different disinfectants.

The authors explain the chemistry, effectiveness, dosing, equipment and system-design requirements for each disinfectant included in the handbook. In addition, references are included at the end of each chapter to provide additional resources for further investigation.

The “Handbook of Chlorination and Alternative Disinfectants” serves as a staple to the water and wastewater industries in the United States. Most professionals keep a copy of the book on their shelves for reference.

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