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EHA : Yearkbook 2009
EHA YEARBOOK 2009 participate in the project and provide their contact details. A reply paid envelope was provided. The participants were informed that no additional personal information would be required, nor would any information that could identify any household be passed on to any third party. Of the 78 letters sent, 38 responses were received which equated to a 51 % response rate. Of the 38 respondents 28 indicated a willingness to participate and have their AWTS surveyed, however, due to resource constraints the first 15 only of these respondents were selected for participation in the survey. The 15 chosen participants were all contacted by telephone to arrange a mutually convenient time for collection of the survey sample. The survey effluent samples were collected in accordance with the Guidelines for Aerated On-Site Wastewater Treatment Systems (EPA Victoria 2002) and A Guide to the Sampling and Analysis of Waters, Wastewaters, Soils and Wastes (EPA Victoria 2000). Effluent samples were collected from mid to late morning on five days between 31 July 2007 and 8 August 2 0 0 7, from each of the AWTS’s final discharge chamber. Polyethylene bottles were used to collect samples for Biochemical Oxygen Demand (BOD) (1000mL container) and suspended solids (SS) (500mL container). As no properties discharged effluent directly to the surface E. coli and chlorine residual were not tested. Table 2 provides the list of the types or models of AWTS that were sampled in the survey. Personal protective equipment such as plastic disposable gloves, anti-bacterial soap, masks (conforming to Australian Standard AS 1715 ) to prevent inhalation of dusts and aerosols, eye protection and appropriate outer clothing were used (EPA Victoria 2000). After collection the samples were immediately placed in an esky with ice and sealed to maintain a temperature of between 1°C and 4°C, and transported within 24 hours to the laboratory (EPA Victoria 2000). The samples were analysed by a National Association of Testing Authority (NATA) registered laboratory. Results Biochemical Oxygen Demand The results for BOD for all systems are outlined in Figure 1. These results revealed that 7 out of the 15 systems, or 47%, that complied with the E PA Victoria effluent standard of <20 mg/L. Both the OzziKleen and the sand filter systems met the E PA Victoria effluent standards for BOD. Fifty percent of the Envirosep SP2000 and the Septech 2000 systems met the effluent standards. The Envirosep SP2000 had a mean age of 4.8 years and the Septech 2000 was considerably older with a 10 year mean age. The oldest systems tested were the Tayl e x Clearwater 80s with a mean system age of 14.3 years. Only one Enviro-Cycle was sampled and it had the lowest age of 1 year, however, this system did not meet the E PA Victoria BOD effluent standard. The next youngest system sampled was the sand filter (not an AWTS) and met the BOD standard. Table 3 outlines the BOD result by type of system and age. The results for SS for all systems are outlined in Figure 2. These results were similar to those for BOD in that 47% of systems sampled met the effluent standard of < 30 mg/L. The OzziKleen and sand filter systems both met the standard but the Tayl e x Clearwater 80 did not meet the standard. The highest results were for one Envirosep SP2000 (470 mg/L) and two Tayl e x Clearwater 80 systems (400 mg/L and 5000 mg/L respectively). The reading of 5000 mg/L was checked with the laboratory. The Envirosep SP2000 and Tayl e x Clearwater 80 models did not meet the standard. The most Table 2: Types of AWTS included in the survey System/Model Certificate of Approval Number Envirosep SP2000 057/98 Enviro-Cycle 31/92 OzziKleen 78/01 Sandfilter 1.2/03 Septech 2000 026/99 Taylex Clearwater 80 15/82 Table 3: Compliance rate for systems surveyed for BOD and mean system age Biochemcial Oxygen Demand Enviro Sep SP2000 (x6) Enviro-Cycle (x1) OzziKleen (x2) Sandfilter (x1) Septech 2000 (x2) Taylex Clearwater 80 (x3) Pass 50% 0% 100% 100% 50% 0% Fail 50% 100% 0% 0% 50% 100% System Mean Age (yrs) 4.8 1 2.5 1.5 10 14.3 Aerated Wastewater Treatment Systems: (continued)
Annual Review and Yearbook 2008
EHA Yearbook 2010