If permitted a simple wet and dry pit should see to most of your needs. Simple to construct, you just excavate an area around a metre square, and at least 20 cm deep. Clearly rope off and mark the pit, and make sure it is placed so that people will not be falling in it every two seconds.
Cover with a layer of interlaced sticks and a filter layer of grass/ leaves etc. These layers should be renewed daily.

When you have finished with the pit, it should be filled in with earth and completely covered. It should then be marked with a sign placed into the ground at that point with a date on which it was created.