Patent ID: 7008531

Claim:
A recirculating water system comprising: (i) water, an adjuvant selected from the group consisting of dodecylamine and salt thereof, a polyquaternary ammonium compound comprising a repeat unit of the formula: wherein: R 4 , R 5 , R 6 and R 7 each independently is C 1-6 -alkyl optionally substituted by hydroxy; Q 2− is a divalent counter ion, two monovalent counter ions or a fraction of a polyvalent counter ion sufficient to balance the cationic charge in the repeat unit; and a, b and t each independently is 1 to 4; and polymeric biguanide; and (ii) a means for recirculating (i); wherein the adjuvant, polyquaternary ammonium compound and polymeric biguanide are dissolved in the water and wherein the adjuvant, polyquaternary ammonium compound, and polymeric biguanide are present in an amount effective in inhibiting the growth of or killing algae, bacteria, and/or fungi in the recirculating water system without affecting water clarity.