T he remaining fraction is greywater (e.g 80%) and is usually surface irrigated via a manually moved sprinkler. fu noted previously with the older split systems, the inappropriate discharge of greywater is of particular co ncern to Local Authori ties.
D 0-5 septics / yr (Crows Nest, Kilcoy, Toov.oorrba)
1 5-10 septics / yr (Esk, Gatton) D 10-25 septics / yr (Brisbane, Laidley, Pine Rivers, Redland) D 25-50 septics / yr (Caloundra, Ipswich, Logan) 1!1 50-100 septics / yr (Beaudesert, Maroochy) D 100-150 septics / yr (Caboolture, Noosa)
Reported AWTS and Sand Filter I 150-200 septics / yr (Gold Coast) Failures 4% 5% The breakdown of reported AWTS 9% and SF system failures per year in SEQ is shown in Figure 8. 'Failure' varied from 0 systems to 700 systems per year. The data presented in Figure 8 needs to be co nsidered in the co ntext of the failure classification used by each Local Authority, and whether or not aerobic systems are inspected Figure 7. Number of reported failures per year regularly. For example, Kilcoy reported for septic systems. Pie slice -% of total septic no AWTS and SF system failures for systems in SEQ. the last year, however they classify a failure as ' lack of maintenance' and do not carry out a regular monitoring faecal col ifor ms (i.e. <30cfu / 100mL). programme. Therefore the likelihood of Although a small number of systems were system failure being detected is much lower sampled (27), results from the study than other more proactive Councils, such as suggested a trend toward poor performance Caloundra. in systems that were not user-friendly and irregularly maintained. T his trend was also Although effiu ent quality monitoring of observed by Local Authorities who believed AWT S and SF systems is not a statutory that lack of appropriate maintenance requirement, some Councils that monitor caused most of the system failures reported. aerobic system effluent often rated ' nonAlso the peak or shock loads into ATWS compliance' as a fo rm of failure. However, were associated with poor effluent qual ity some Councils acknowledged th at nonor poorly functioning mechanical pares. compliance with effluent quality criteria Several Local Au thorities stated that the was not necessarily an accurate gauge of a septic system was not necessarily the most system's perfo rmance. Errors in sampling problematic system in regards to surface and the inherent temporal variability in water contamination. They argued that wastewater quality are fac tors chat could when A W T S and sand filcers fail, they will cause effi uent quali ty data to be an unreliable guide to the system's treatment capabilities. Furthermore, the criteria of 20mg/L BOD and 30mg/L suspended solids (On-site Sewerage Code 2003), which were the most commonly tested parameters by Councils, relates to direct discharge into waterways, and therefore may not be especially releva nt fo r discharge onto vegetated areas. A survey of 2 16 aerobic systems in Queensland by T ully and Beavers (2001 ) indicated an underperfo rmance of aerobic systems with only 30% of systems achieving the effiuent quality criteria fo r BOD, suspended solids and faecal coliforms. Khalife and Dharmappa (1 996) found a majority of the AWTS tested in NSW exceeded the effiuent quality guidelines, with only 50% of systems satisfying the limit fo r 72 JUNE 200s
water
surface-irrigate poorly treated effluent making them a similar if not greater environmental and public health risk than poorly performing septic systems. There was often little Local Authority confidence in service agents as inadequate maintenance or lack of care by the agents was commonly observed by Plu mbing Inspecto rs.
Greywater Systems As identified earli er in the text, split greywacer/blackwacer (septic) systems comprise the majority of complain ts and failures reported by Local Authority officers. Inappropriate greywater discharge was singled out as one of the most problematic issues associated with on-site systems. Many greywater systems disperse effiuenc via surface irrigation using a movable hose and sprinkler. It was reported that sprin klers were not being moved frequen tly and/or were located in unsui table areas (gutters, sro rmwater drains). The volume of water being discharged via greywater systems is up to fo ur times greater than that going into blackwater trenches (i. e compare 20% to 80% of household water), however, the concentrations of pathogens, nutrients, solids and BOD are likely to be much less than in surcharging septic tank effluen t. Figure 9 shows that almost 70% of the Local Authorities believe that the frequency of inappropriate discharge of greywater systems was medium or high. Some examples include hoses discharging greywarer being directed into gutters, stormwater a 0-5 aerobics / yr (Booriah, Brisbane, Crows Nest, Esk, Gatton, pswich, Kilcoy, rmba) drains, kerbside grass verges, • 5-50 aerobics / yr (Laidley, Redland) roadways or the neighbours' a 50-200 aerobics/ yr (Logan) properties. O ther surveys have a 200-300 aerobics/ yr (Beal.desert, Noosa) also iden ti fied inappropriate greywater discharge as an issue • 300-400 aerobics/ yr (Gold Coa st) (Arnold & Gallasch, 2001 ; a 400-500 aerobics / yr (Maroochy) Rawlinson, 1994). The other • 500-700 aerobics / yr (Caboolture, Pine Rivers) common definition of greywarer failure used by Local Authori ties • >700 aerobics / yr (Caloundra) was odour from blocked or overflowing grease-traps. 6%
Rented Properties and Commercial Systems
28%
15%
24%
Figure 8. Number of reported failures per year for AWTS and Sand Filters. Pie slice - % of total aerobic systems in SEQ.
The number of rental dwellings with OWTS was diffic ult to quantify although fo rty-five percent of Local Authorities rared the frequency of OWTS installed in rented dwellings as medium or high.