Abstract: Provided is a solid precipitation reactor useful for waste-water treatment. The reactor can include a reaction chamber configured to receive feedwater and to allow particulates to at least partially precipitate from the feedwater to form an effluent, and a membrane module having at least one membrane filter configured to receive effluent from the reaction chamber and to filter suspended particulates from the effluent to produce a permeate and a concentrate. The concentrate can be reintroduced to the re-action chamber to allow additional particulates to precipitate. Systems and methods for wastewater treatment, and methods for regenerating a zeolite cation exchanger, using the solid precipitation reactor are also provided.