Innovative Solutions for Decentralized Wastewater Treatment

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Courtesy of Premier Tech Aqua

Chlorination and UV light are currently the most common methods used for disinfection of wastewater. While these processes are generally well-adapted to community or municipal installations, their operation and maintenance needs present some limitations to assure sustainable performance at the level of individual wastewater treatment systems. As reported in many papers (U.S. EPA. 1999), use of chlorine for wastewater disinfection presents environmental risks related to toxicity for aquatic life and trihalomethane (THM) compounds formation according to organic content of treated effluent. Also, to assure disinfection efficiency, chlorine must be added 011 a regular basis that is often neglected because few regulations include mandatory maintenance requirements.

Use of UV light for wastewater disinfection presents less risk than chlorination because 110 chemical reacts with organic matter. However, the reliability of UV disinfection performance is subjected to transmissivity of UV light in the wastewater to be treated that is influenced by many factors acting in different ways. The content in suspended solids (TSS) reduces UV light efficiency by masking UV rays for bacteria inactivation (NSFC, 1998). Presence of iron and manganese in more than 0.3 and 0.05 mg/L respectively, absorbs UV light and calcium (hardness) promotes, in combination with iron, fouling of quartz mbe that it reduces transmission of UV light (Selmaoui and al.. 2001). Fouling of quartz mbe is also increased by other factors like intermittent flow. Flow interruption (vacation, week-end. etc.) increases the wastewater temperature in UV unit promoting carbonates precipitation 011 quartz tube (Whitby, 2002). Also, the reject of backwash from drinking water treatment system (ex: softener) in septic system has a major impact 011 quartz tube fouling. Considering that these previous factors are dependant on the quality of drinking water, family life habits and wastewater treatment system used in front of UV unit, the performance of UV disinfection, as well as the time required for quartz mbe fouling, will vary from site to site.

In such conditions, as previously discussed, it clearly appears that management of chlorination or UV disinfection systems 011 an individual basis is too costly (maintenance requirements varying from site to site) to allow a safe disinfection performance in all conditions in the field. In view of these limitations, a need remains for a low maintenance disinfection system suitable for an individual wastewater treatment system. This paper presents the solution developed by Premier Tech Environment (PTE) that meets this need.

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