Abstract: Water treatment apparatus having a raw water inlet and a treated water outlet and at least a first and second water treatment tank plus conduit means for passing water from the inlet to the outlet through the first and second tanks in parallel flow relation. The tanks are automatically regenerated in sequential, alternating intermittent manner in response to predetermined criteria. The tank being regenerated is connected to prevent flow from said tank through the outlet, while the tank not being regenerated is connected to provide flow through the outlet. Accordingly, continuous water treatment, with alternating, intermittent regeneration of the tanks, may be provided.

Abstract: The method of purifying spent brine from the regeneration of ion exchange resin, for example resin in water softeners. The method comprises acidifying the spent brine to a pH of less than 3 with an acid other than sulfuric acid, which acid is preferably chosen from at least one acid which forms a calcium salt that is more water soluble than calcium sulfate. One passes the brine through a nanofiltration membrane to purify the brine by separating from it a waste stream which comprises the majority of the polyvalent ions present, so that the purified brine has most of its contaminating polyvalent ions removed.

Abstract: A low salt level sensor comprising a float within a brine tank, apparatus for detecting whether the float has risen in response to the addition of a predetermined amount of water to the brine tank to a height such that an adequate supply of salt is present in said brine tank and apparatus for indicating if the float has not risen high enough. A method of detecting whether the salt level is low in the brine tank of a water treatment system is also described. According to this method, brine is removed from the brine tank and a predetermined amount of water is added. A determination is then made as to whether the brine level has reached a height such that an adequate supply of salt is present in the brine tank and an indication is provided if the brine level is below this height.

Abstract: Water treatment apparatus having a raw water inlet and a treated water outlet and at least a first and second water treatment tank plus conduit means for passing water from the inlet to the outlet through the first and second tanks in parallel flow relation. The tanks are automatically regenerated in sequential, alternating intermittent manner in response to predetermined criteria. The tank being regenerated is connected to prevent flow from said tank through the outlet, while the tank not being regenerated is connected to provide flow through the outlet. Accordingly, continuous water treatment, with alternating, intermittent regeneration of the tanks, may be provided.

Abstract: A water treatment system is provided including a service step, a regenerating step and a rinse step. The service step includes introducing water to be treated into the inlet, through a treatment medium and out the outlet to a service location. If a prolonged period of idleness is determined automatically, a rinse step is automatically provided by which an amount of water to be treated is introduced into the inlet, through the treatment medium and out of the outlet to drain.

Abstract: A water softening system is provided including a service step, a regenerating step and a rinse step. The service step includes introducing relatively hard water into the inlet, through an ion exchange resin and out the outlet to a service location. The regenerating step includes introducing a brine solution into the inlet, through the resin and out the outlet to drain. Prior to the service step, an automatic rinse step is provided by which an amount of the relatively hard water is introduced into the inlet, through the softening medium and out of the outlet to drain.

Abstract: An excellent reverse osmosis membrane having a high flux with superior chlorine resistance and low salt passage can be obtained by interfacially condensing a water soluble aromatic polyamide prepolymer with an essentially monomeric, aromatic, amine reactive polyfunctional acyl halide. The polyamide prepolymer may be prepared through the condensation reaction of an aromatic diamine and an aromatic anhydride acyl halide. Preferably the amide prepolymer, prepared from metaphenylene diamine and trimelletic anhydride acid chloride, is reacted with trimesoylchloride to form the thin film membrane of the subject invention.

Abstract: A process is provided for controlling the recharging of a water conditioner. Water usage during selected fractions of a predetermined period of time is sensed. Information signifying the water usage during the selected fractions is stored. A time fraction is automatically determined, based on the stored information, when water is unlikely to be used. A selected parameter, such as volume of water used since recharging, is sensed to determine if recharging is required. The water conditioner is recharged during the automatically determined time fraction if the selected parameter indicates that recharging is required.

Abstract: A novel electronic control circuit which utilizes an improved and greatly simplified arrangement for producing the reference voltage and which includes a probe which includes two pairs of spaced electrodes which are connected in a bridge circuit so that both a reference signal and a control signal is obtained for closing an energizing circuit and latch it until it is time for regeneration and in which the regeneration will occur only at preset times so as to not interfere with normal use.

Abstract: A novel electronic control circuit which includes a probe for detecting the conductivity in ion exchange material in a water softener and wherein the probe includes two pairs of spaced electrodes which are connected in a bridge circuit and connected so as to close an energizing circuit and latch it until it is time for regeneration and wherein the regeneration is controlled so that it will occur only at those times which are preset as, for example, during the night when the regeneration will not interfere with normal use of the water supply.