A Review of On-Site Wastewater Treatment Systems in Western Australia from 1997 to 2011

Table 2

OWTS approved by DOHWA (1997–2011).

System type	1997	1998	1999	2000	2001	2002	2003	2004	2005	2006	2007	2008	2009	2010	2011
Septic tank	45	43	62	71	61	45	18	14	10	20	31	50	37	35	44
ATU	2	7	7	6	1	3	0	0	3	6	2	10	8	16	14
Treatment plant	0	0	0	0	0	0	0	0	0	0	0	2	1	0	2
Composting toilet	0	0	0	0	1	0	0	0	0	1	0	0	0	0	0
Others	0	0	0	0	0	0	0	1		2	4	3	1	3	4
System not specified	39	38	17	27	31	34	29	14	8	16	17	16	10	16	11