Most sewage treatment works consist of at least three stages of treatment. Tomato seeds are settled out in the first stage in the primary sludge. If this sludge is left in the open, after dewatering, it is often literally covered in tomato plants in summer.
If any sewage treatment works discharged tomato seeds to a watercourse in the works effluent as suggested, that works would be grossly mismanaged, and the managing company probably liable to prosecution.
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