Water Treatment Process and Plant Using Ballasted Flocculation and Settling

• US 20100096335A1
• Filed: 12/26/2007
• Published: 04/22/2010
• Est. Priority Date: 12/29/2006
• Status: Active Grant

• Current Assignee: Veolia Water Solutions & Technologies Support
• Original Assignee: OTV SA SA
• Inventors: Dahl, Claus, Levecq, Celine, Ursel, Valey, Beaudet, Jean-Francois, Sauvignet, Philippe
• Granted Patent: US 8,617,400 B2
• Time in Patent Office: Days
• US Class Current: 210/709
• CPC Class Codes: B01D 21/0045 Plurality of essentially parallel plates
• CPC Class Codes: B01D 21/06 with rotating scrapers
• CPC Class Codes: B01D 21/08 provided with flocculating compartments
• CPC Class Codes: B01D 21/34 Controlling the feed distribution; Controlling the liquid level ; Control of process parameters
• CPC Class Codes: C02F 1/004 using large scale industrial sized filters
• CPC Class Codes: C02F 1/006 Water distributors either inside a treatment tank or directing the water to several treatment tanks; Water treatment plants incorporating these distributors, with or without chemical or biological tanks for settling tanks B01D21/24
• CPC Class Codes: C02F 1/28 by sorption using ion-exchange C02F1/42; sorbent compositions B01J
• CPC Class Codes: C02F 1/38 by centrifugal separation
• CPC Class Codes: C02F 1/42 by ion-exchange ion-exchange in general B01J
• CPC Class Codes: C02F 1/52 by flocculation or precipitation of suspended impurities C02F1/463 takes precedence
• CPC Class Codes: C02F 1/5209 Regulation methods for flocculation or precipitation
• CPC Class Codes: C02F 1/5281 Installations for water purification using chemical agents
• CPC Class Codes: C02F 1/66 by neutralisation; pH adjustment for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58
• CPC Class Codes: C02F 2201/003 Coaxial constructions, e.g. a cartridge located coaxially within another
• CPC Class Codes: C02F 2209/001 Upstream control, i.e. monitoring for predictive control
• CPC Class Codes: C02F 2209/40 Liquid flow rate
• CPC Class Codes: C02F 2301/043 Treatment of partial or bypass streams
• CPC Class Codes: C02F 2305/12 Inert solids used as ballast for improving sedimentation C02F3/1226 takes precedence
• CPC Class Codes: C02F 9/00 Multistage treatment of water, waste water or sewage

Abstract

A method for treating wastewater using a ballasted flocculation technique includes continuously measuring the concentration of suspended solids, organic matter or other impurities in the water to be treated prior to directing the water to be treated to a flocculation tank. Based on this measurement, the amount of ballast necessary to obtain treated water of a predetermined quality is then calculated. In the flocculation tank, ballast and a flocculating reagent are added to the water to form a water-floc mixture. The water-floc mixture is directed to a settling tank where a sludge-ballast mixture is settled. The sludge-ballast mixture is directed to a mixing tank and then to a separator to separate the ballast from the sludge. The separated ballast is directed to the flocculation tank. The separated sludge is directed to the mixing tank when the level of sludge-ballast mixture in the mixing tank is lower than a predetermined level.

Claims

1-50. -50. (canceled)

51. A method of treating wastewater containing colloidal, dissolved or suspended impurities using a ballasted flocculation technique comprising:

a. directing water to be treated into a flocculation tank;

b. injecting ballast and a flocculating reagent into the flocculation tank containing the water to be treated to form a water-floc mixture;

c. directing the water-floc mixture into a settling tank, settling a sludge-ballast mixture in the settling tank, and producing treated water;

d. directing the sludge-ballast mixture to a mixing tank and mixing the sludge-ballast mixture in the mixing tank;

e. directing the sludge-ballast mixture from the mixing tank to a separator and separating the ballast from the sludge;

f. directing the separated ballast to the flocculation tank for reuse;

g. directing at least a portion of the sludge from the separator to the mixing tank;

h. continuously measuring the concentration of suspended solids, organic matter or other impurities in the water to be treated prior to the water entering a flocculation tank; and

i. calculating the amount of ballast necessary to obtain treated water of a predetermined quality based on the measured concentration of suspended solids, organic matter or other impurities in the water to be treated.

52. The method of claim 51 including measuring the amount of ballast present in the sludge-ballast mixture settled in the settling tank or in the water-floc mixture in the flocculation tank.

53. The method of claim 52 including injecting the flocculation tank with ballast when the amount of ballast present in the sludge-ballast mixture or in the water-floc mixture is lower than the amount of ballast necessary to obtain treated water of the predetermined quality.

54. The method of claim 53 including automatically injecting the flocculation tank with ballast when the amount of ballast present in the sludge-ballast mixture or in the water-floc mixture is lower than the amount of ballast necessary to obtain treated water of the predetermined quality.

55. The method of claim 51 including utilizing the measurement of the concentration of suspended solids, organic matter or other impurities in the water to be treated to calculate the amount of flocculating reagent necessary to obtain treated water of the predetermined quality.

56. The method of claim 55 including continuously adjusting the amount of flocculating reagent injected into the flocculation tank based, in part at least, on the amount of ballast necessary to obtain treated water of the predetermined quality.

57. The method of claim 51 including continuously injecting a predetermined amount of coagulating reagent and a pH adjusting reagent into the water to be treated prior to directing the water to be treated into the flocculation tank.

58. The method of claim 51 wherein calculating the amount of ballast necessary to obtain treated water of the predetermined quality includes utilizing the equation:

Y=ax^b+C;

wherein Y is the ballast concentration necessary to obtain treated water of the predetermined quality, a is between 0.4 and 1, b is between 0.3 and 1, C is between 0 and 2, and x is the measured concentration of suspended solids, organic matter or other impurities in the water to be treated.

59. The method of claim 51 including adjusting the flow rate of the portion of the sludge being directed from the separator into the mixing tank to maintain a predetermined level of the sludge-ballast mixture in the mixing tank.

60. The method of claim 51 wherein injecting the ballast and the flocculating agent with the water to be treated includes:

a. directing water to be treated into a peripheral zone of the flocculation tank and injecting the ballast into the peripheral zone of the flocculation tank;

b. directing the water and ballast into an immersed flow-guide structure in the flocculation tank and injecting the flocculating agent in the flow-guide structure; and

c. mixing the water and ballast with the flocculating agent in the flow-guide structure to form the water-floc mixture.

61. The method of claim 51 wherein the ballast includes a granular material having adsorption properties, ion exchange properties, or molecular exchange properties.

62. The method of claim 61 wherein the ballast includes active carbon powder.

63. The method of claim 51 including measuring the level of the sludge-ballast mixture present in the mixing tank and directing at least a portion of the sludge separated by the separator to the mixing tank when the measured level of sludge-ballast mixture in the mixing tank is lower than a predetermined level.

64. The method of claim 51 wherein directing at least a portion of the sludge from the separator to the mixing tank includes directing at least some of the sludge separated by the separator to a storage tank, and based on the level of the sludge-ballast mixture in the mixing tank, directing the separated sludge from the storage tank to the mixing tank.

65. The method of claim 51 wherein the flocculation tank includes a vertically oriented mixing tube having an open top, an open bottom and a mixer disposed within the mixing tube, and wherein the method includes directing the water to be treated into the open top of the mixing tube and downwardly through the mixing tube to mix the ballast and the flocculating reagent with the water as the water moves downwardly through the mixing tube.

66. The method of claim 64 including creating a downwardly axial flow through the mixing tube such that the water, ballast and flocculating reagent move downwardly and axially through the mixing tube.

67. The method of claim 64 including injecting the flocculating reagent into the mixing tube.

68. The method of claim 64 wherein the water-floc mixture moves downwardly through the mixing tube and exits the bottom thereof and the method further includes disrupting the flow of the water-floc mixture exiting the mixing tube by positioning a static device in the path of the water-floc mixture.

69. The method of claim 64 wherein the water-floc mixture moves downwardly through the mixing tube and exits the bottom thereof and is recirculated upwardly outside of the mixing tube and thereafter reenters the open top of the mixing tube such that a circulating process occurs wherein the water-floc mixture is continuously directed downwardly through the mixing tube and upwardly outside of the mixing tube and back into the open top of the mixing tube.

70. A wastewater treatment system comprising:

a. a flocculation tank provided with at least one agitator;

b. a ballast inlet to direct ballast into the flocculation tank wherein the ballast is a granular material having adsorption properties, ion exchange properties, or molecule exchange properties;

c. a flocculating agent inlet to direct flocculating agent into the flocculation tank;

d. a settling tank having an outlet for treated water disposed downstream of the flocculation tank;

e. an mixing tank having at least one agitator, the mixing tank disposed downstream from the settling tank;

f. a separator for separating ballast and sludge from a sludge-ballast mixture;

g. a first sensor to continuously measure the concentration of suspended solids, organic matter or other impurities in water to be treated disposed upstream from the flocculation tank; and

h. at least one calculator to continuously analyze the measurements taken by the first sensor and determine the amount of ballast necessary to obtain the treated water of a predetermined quality.

71. The system of claim 70 including a recirculation line for recirculating at least a portion of the sludge from the separator to the mixing tank and wherein the separator includes a ballast outlet for directing at least a portion of the ballast from the separator to the flocculation tank.

72. The system of claim 70 including a second sensor disposed upstream of the separator and downstream from the first sensor to continuously measure the amount of ballast in the sludge-ballast mixture.

73. The system of claim 70 including an automatic ballast injection device to automatically inject ballast into the flocculation tank.

74. The system of claim 70 including an automatic flocculating reagent injection device to automatically inject flocculating reagent into the flocculation tank.

75. The system of claim 70 wherein the flocculation tank includes a flow-guide structure including a mixer.

76. The system of claim 70 wherein:

the settling tank is a lamellar settling tank and includes a submerged spillway and a splitting structure; and

the splitting structure including;

at least two parallel plates, wherein each plate is disposed on one side of the submerged spillway; and

a series of transverse plates disposed transverse to the parallel plates.

77. A wastewater treatment system for treating water, comprising:

a. a flocculation tank provided with at least one agitator;

b. a ballast inlet for injecting ballast into the water to be treated;

c. a flocculating agent inlet for injecting a flocculating agent into the water to be treated;

d. wherein the wastewater treatment system mixes the ballast and flocculating agent with the water in the flocculating tank resulting in a water-floc mixture;

e. a settling tank disposed downstream from the flocculating tank wherein a sludge-ballast mixture settles and wherein the settling tank produces treated water that is directed from the settling zone; and

f. a separator for receiving the sludge-ballast mixture and separating ballast and sludge from the sludge-ballast mixture such that at least a portion of the ballast can be recycled and mixed with the water being treated.

78. The wastewater treatment system of claim 77 further including:

a. a first sensor to continuously measure the concentration of suspended solids, organic matter or other impurities in the water to be treated disposed upstream from the flocculation tank; and

b. at least one calculator for continuously analyzing the measurements taken by the first sensor to determine the amount of ballast necessary to obtain treated water of a predetermined quality.

79. The wastewater treatment system of claim 77 further including:

a. a mixing tank disposed downstream from the settling tank;

b. a first line operatively interconnected between the settling tank and the mixing tank for directing the sludge-ballast mixture from the settling tank to the mixing tank; and

c. a second line operatively interconnected between the mixing tank and the separator for directing the sludge-ballast mixture from the mixing tank to the separator.

80. The wastewater treatment system of claim 79 further including:

a. a sludge storage tank for receiving separated sludge from the separator and holding the separated sludge; and

b. a third line operatively interconnected between the sludge storage tank and the mixing tank for directing sludge from the sludge storage tank to the mixing tank.

81. The wastewater treatment system of claim 77 further including:

a. a first sensor to continuously measure the concentration of suspended solids, organic matter or other impurities in the water to be treated disposed upstream from the flocculation tank;

b. a second sensor disposed upstream of the separator for continuously measuring the amount of ballast in the sludge-ballast mixture;

c. a mixing tank disposed downstream from the settling tank;

d. a first line operatively interconnected between the settling tank and the mixing tank for directing the sludge-ballast mixture from the settling tank to the mixing tank; and

e. a second line operatively interconnected between the mixing tank and the separator for directing the sludge-ballast mixture from the mixing tank to the separator.

82. The wastewater treatment system of claim 81 further including:

a. a sludge storage tank for receiving separated sludge from the separator and holding the separated sludge; and

b. a third line operatively interconnected between the sludge storage tank and the mixing tank for directing sludge from the sludge storage tank to the mixing tank;

c. a third sensor associated with the mixing tank to sense the level of the sludge-ballast mixture in the mixing tank; and

d. wherein the wastewater treatment system is operative to direct sludge from the sludge storage tank into the mixing tank through the third line when the level of sludge-ballast mixture in the mixing tank is below a predetermined level.

83. The wastewater treatment system of claim 81 further including:

a. a mixing tube disposed in the flocculation tank;

b. the mixing tube including an open top, and an open bottom which permits the water-floc mixture to flow vertically through the mixing tube;

c. a mixer disposed in the mixing tube for mixing the water, ballast and flocculating agent to yield the water-floc mixture; and

d. wherein the flocculation tank includes a wall structure and wherein the mixing tube is disposed inwardly of the wall structure of the flocculation tank so as to define a peripheral zone between the wall of the flocculation tank and the mixing tube.

88. The wastewater treatment system of claim 77 including a service water line leading to the separator for directing service water to the separator where service water is mixed with the sludge-ballast mixture received by the separator such that the service water removes organic matter from the ballast and dilutes the sludge separated by the separator.

89. The wastewater treatment system of claim 81 wherein the second sensor is operative to sense the ballast concentration of the sludge-ballast mixture passing in the second line or the sludge-ballast mixture in the mixing tank.

90. The wastewater treatment system of claim 77 further including:

a. a splitting structure disposed at an inlet of the settling tank;

b. the splitting structure including;

i. a first set of two parallel plates with each plate disposed on one side of a submerged spillway provided between the flocculation tank and the settling tank; and

ii. a series of transverse plates, each extending between the two plates of the first set of plates;

the transverse plates extending in a generally transverse direction relative to the first set of plates and extending in a generally parallel direction relative to each other.

91. The wastewater treatment system of claim 83 wherein the flow distributing device is disposed at least 200 mm from the mixer.

92. The wastewater treatment system of claim 89 wherein said flow distributing device includes at least one diametral plate having a height H and defining at least two compartments.

93. The wastewater treatment system of claim 92 wherein each compartment has a theoretical width B and a ratio of H/B is between approximately 1 and approximately 2.

85. The wastewater treatment system of claim 84 further including a flow distributing device disposed adjacent the open bottom of the mixing tube for distributing the flow of the water-floc mixture to the peripheral zone of the flocculation tank.

86. The wastewater treatment system of claim 85 further including a flow distributing device disposed at least partially within the mixing tube adjacent the open bottom thereof.

87. The wastewater treatment system of claim 86 wherein the flow distributing device includes a plurality of side-by-side channels that are at least partially disposed within the mixing tube.

94. A method for treating wastewater comprising:

a. directing water to be treated to a flocculation tank;

b. directing ballast and a flocculating reagent into the flocculation tank and mixing the ballast and the flocculating reagent with the water to be treated to form a water-floc mixture;

c. directing the water-floc mixture to a settling tank disposed downstream from the flocculation tank;

d. settling the floc in the water-floc mixture to form a sludge-ballast mixture in the settling tank;

e. directing the sludge-ballast mixture to a separator and separating the ballast from the sludge; and

f. recycling at least a portion of the ballast and mixing the recycled ballast with the water to be treated.

95. The method of claim 94 further comprising:

a. continuously measuring the concentration of suspended solids, organic matter or other impurities in the water to be treated with a first sensor prior to directing the water to be treated to the flocculation tank;

b. continuously analyzing the measurements taken by the first sensor and calculating the amount of ballast necessary to obtain treated water of a predetermined quality.

96. The method of claim 94 further comprising directing the sludge-ballast mixture from the settling tank to a mixing tank prior to directing the sludge-ballast mixture to the separator

97. The method of claim 96 further comprising:

a. directing the separated sludge to a sludge storage tank;

b. sensing the level of the sludge-ballast mixture in the mixing tank; and

c. directing the separated sludge to the mixing tank when the level of sludge-ballast mixture in the mixing tank is below a predetermined level.

98. The method of claim 94 further comprising:

a. directing service water to the separator; and

b. mixing the service water with the sludge-ballast mixture in the separator such that the service water removes organic matter from the ballast and dilutes the sludge separated by the separator.

99. The method of claim 95 wherein calculating the amount of ballast necessary to obtain treated water of the predetermined quality includes utilizing the equation:

Y=0.4208×

X^0.3667;

wherein Y is the ballast concentration necessary to obtain treated water of the predetermined quality and X is the measured concentration of suspended solids, organic matter or other impurities in the water to be treated.

100. The method of claim 94 further comprising:

a. directing ballast, flocculating reagent, and water to be treated through a mixing tube disposed in the flocculation tank;

b. directing the water-floc mixture out of the mixing tube; and

c. directing the water-floc mixture to a peripheral zone of the flocculation tank disposed outside of the mixing tube and back into the mixing tube.

96-1. The method of claim 94 further comprising continuously measuring the amount of ballast in the sludge-ballast mixture with a second sensor before directing the sludge-ballast mixture to the separator.