What suitable size and type of septic tank

Septic tank sizing depends on flow rate. I suggest you check your local codes as they will likely have something to say about it.
As for kitchen waste lines, run them to a grease/soap trap seperate from the septic tank. All that soap and grease can kill the bacteria in a septic tank and will clog it up. Again sizing depends on flow and on how often you are willing to clean it out. Which is such a fun job.

First of all, in Florida, septic tanks are normally sized to for a 24 hour peak flow detention plus 30% excess. This 30% excess includes 12" from outlet invert to bottom of lid. The effluent is withdrawn via a tee that the intake is 18" under the invert. The middle of the tank carries the clear fluid. The disposal of the effluent is via a leachfield with 24" minimum above the seasonal high ground water for denitrification. (in high ground water conditions, a pump to a mounded system is used) The influent to the septic tank is via a tee, usually about 12" submerged. Too much greases and oil will kill the tank and leach field (especially if you have chlorinated water, the grease will congeal in the leach field). Therefore, for a high grease/oil load, a grease trap is used. The size of the grease trap depends on the frequency of cleaning.

Next, your flow seems borderline high for a septic tank system. (In Florida, septic systems are under 5000 gpd or 2000 gpd for a restaurant) Please consider a small package extended aeration plant or a lagoon system or an alternative to a standard septic tank.

Here are three links of interest - (with the best link being the last one)




Best of luck. Clifford H Laubstein
FL Certified PE #58662