I live in Spain and have a soak away septic system which I am told cannot be emptied. I have problems with smelly drains both in the kitchen and in the bathrooms. I do not weant to use harsh chemicals like bleach as I don't want to upset the bacterial process. Is there anything else I can use that will help eliminate the smells without causing problems with the bacterial process?

You need to determine if this is sewer gas or just rotting hair and debris that is rancid. Sewer gas can be put in check with properly operating P traps. Rotting material can be cleaned out by this receipe. Mix 1/2 cup of table salt with 1/2 cup od baking soda, dump down the drain and then add a cup of vinegar. Allow to bubble and soak over night followed with a bucket of really hot water. The drain should smell great and you eptic field will not suffer.