I do not know where you live or what your local regulations are, but you might investigage an aerobic septic tank and system since the effluent is much purer and less hazardous. You can also add some purification treatment to the effluent and actually have water that can be sprayed into the air for irrigation purposes. 

Other alternative drainfield designs can be found in some of the literature found on the Small Flows WEB site. The link in available on this site.