Waste water treating process

• US 5,098,567 A
• Filed: 12/12/1990
• Issued: 03/24/1992
• Est. Priority Date: 07/31/1987
• Status: Expired due to Fees

• Current Assignee: Nishihara Environmental Sanitation Research Corporation Limited
• Original Assignee: Nishihara Environmental Sanitation Research Corporation Limited
• Inventors: Nishiguchi, Takeshi
• Primary Examiner(s): CINTINS, IVARS C
• Application Number:
  US07/626,385
• Time in Patent Office: 468 Days
• Field of Search: 204/149, 210/605, 210/631, 210/702, 210/717, 210/906, 210/907, 210/614, 210/630
• US Class Current: 210/614
• CPC Class Codes: C02F 1/705 Reduction by metals
• CPC Class Codes: C02F 3/082 Rotating biological contactors
• CPC Class Codes: C02F 3/1215 Combinations of activated sludge treatment with precipitation, flocculation, coagulation and separation of phosphates
• CPC Class Codes: Y02W 10/10 Biological treatment of water, waste water, or sewage
• CPC Class Codes: Y10S 210/906 Phosphorus containing

Abstract

A waste water treatment process wherein an iron contactor or iron contact are immersed in a treatment tank, into which waste water flows. In the treatment tank sulfate reducing bacteria are made to coexist with activated sludge or biofilters, wherein a velocity of flow of agitating stream on the outer surfaces of said iron contactor or contactors is set at 10 to 20 cm/sec, under an aerobic treatment. Iron ions are made to elute from said iron contactor or contactors by utilizing electrochemical iron corrosion through the agency of oxygen concentration cells on the outer surfaces of said iron contactor or contactors on conditions that dissolved oxygen concentration in the treatment tank is 1 to 3.2 mg/l and the oxidation-reduction potential is -200 to -400 millivolts (mV). Under an anaerobic treatment, iron ions are made to elute by utilziing microorganism-corrosion on the outer surfaces of said iron contactor or contactors on condition that dissolved oxygen concentration in the treatment tank is 0 mg/l. Under the aerobic or anaerobic conditions, the iron ions eluting from the outer surfaces of said iron contactor or contactors are combined with ions of phosphoric acid in the waste water to thereby remove phosphorus in the waste water as insoluble salt of iron phosphate.

Claims

1. In a waste water treatment process employing activated sludge or biofilters in aerobic conditions, and then, anaerobic conditions to treat waste water containing phosphate ions, the improvement which comprises:

a. adding activated sludge and sulfate reducing bacteria to the waste water, and immersing an iron contactor in waste water containing phosphate ions flowing into a waste water treatment tank;

b. causing an agitating stream of the waste water to flow over the surface of the iron contactor or contactors at a velocity of 10 to 20 cm/sec.;

c. under aerobic conditions, providing a dissolved oxygen concentration of 1 to 3.2 mg/l and a redox potential within the range from 31 200 to -400 mV to effect corrosion on the surface of said iron contactor, and cause iron ions to elute from said iron contactor;

d. then under anaerobic conditions, holding the dissolved oxygen concentration at 0 mg/l in the treatment tank, the sulfate reducing bacteria acting on the surface of the iron contactor to cause corrosion on the surface of the iron contactor, and eluting iron ions from the iron contactor; and

e. said iron ions eluted from the surface of the iron contactor under said aerobic and said anaerobic conditions, reacting with phosphoric acid ions in the waste water to produce insoluble compounds formed of iron and phosphate ions, and removing said compounds of iron and phosphate ions from the waste water.

2. A process according to claim 1 wherein the ratio of the phosphate flow rate into the treatment tank to the surface area of the iron contactor is in the range of 0.3 to 1.0 g/m² day and the phosphorus removal is at least 90% wherein the total quantity of phosphorus in said waste water containing phosphate ions is measured to determine the phosphate content of said waste water and to determine said phosphate flow rate range.

3. A process according to claim 1 wherein the sulfate reducing bacteria concentration is 10⁵ to 10⁶ cells/ml.

4. A process according to claim 1 wherein the iron contactor is in the form of an iron plate, iron granules, an iron net, an iron tube, an iron bar or an iron disc.