Brewing organic beer

Cleaning of equipment is no different for organic or non organic brewing because you will want to rinse all of the cleaning agent residue from the equipment before use. You need to use a caustic soda based detergent and probably a hypochlorite containing sterilant. It's possible to combine the two and most detergent suppliers have such a formulation. Try Proton chemicals (google) for really good advice on such matters. There isn't to my knowledge a less aggressive approach which works long term because if you use only mild detergents and heat a protein scale will gradually build up and harbour infection.

Your cesspit (and neighbours?) will not thank you for starting brewing. Brewing produces a huge amount of biological effluent in the form of yeast, waste beer, last runnings etc, plus the cleaning chemicals which are (I think) unavoidable. If doing anything other than small scale hobby brewing you may well either overwhelm or kill your cesspit, and possibly both even without the cleaning side of things. Brewers without access to mains drainage usually pump the worst of their effluent to a tank for disposal by road tanker or build a small effluent pre-treatment plant prior to the cesspit.

Only a very rough indication of the lines your enquirer should be thinking along. Particularly with regard to the cesspit you need more expert advice.