US-12623921-B2 - Techniques for managing scale formation in reverse osmosis (RO) and nanofiltration (NF) systems and a hybrid filtration architecture implementing the same

US12623921B2US 12623921 B2US12623921 B2US 12623921B2US-12623921-B2

Abstract

The present disclosure is directed to filtering technologies that combine elements of continuous and batch NF/RO based on the constraints of the end-user facility to achieve a target balance between, for instance, recovery and power consumption, and to reduce long term operating cost of a plant. A method for extending batch operation into a second induction period with antiscalant injection is also disclosed herein, with the second induction period allowing for yet higher water recovery.

Inventors

Stanton Russel Smith

Assignees

CLEAN H2O TECHNOLOGIES, LLC

Dates

Publication Date: 20260512
Application Date: 20200527

Claims (10)

1 . A method for operating a filtration system, the filtration system having an inlet fluidly coupled to at least one feed stream, at least one filter membrane fluidly coupled to the inlet to receive feed water from the at least one feed stream and at least one pump to generate a pressure to displace the feed water from the at least one feed stream into the at least one filter membrane and produce an output permeate stream, the method comprising: prior to adding an antiscalant to the at least one feed stream, causing a first driving signal to be provided to the at least one pump to cause the generated pressure to produce the output permeate stream at a recovery rate that is substantially equal to a first target recovery rate during a first period of time, the first target recovery rate being greater than a maximum non-scaling recovery rate for the at least one filter membrane and less than 100%, wherein the maximum non-scaling recovery rate is a water recovery at which scaling initiates or when super-saturation of a scaling compound of interest first occurs while maintaining the first target recovery rate, determining when a predetermined moment will occur, the predetermined moment associated with when a pre-antiscalant maximum non-scaling recovery state will be reached for the at least one filter membrane; and in response to determining when the predetermined moment will occur, causing one or a plurality of antiscalant doses to be provided to the at least one filter membrane prior to the pre-antiscalant maximum non-scaling recovery state being reached to increase an amount of time between when a post-antiscalant maximum non-scaling recovery state is reached and when subsequent scaling and/or fouling of the at least one filter membrane occurs; and causing a second driving signal to be provided to the at least one pump to cause the generated pressure to produce the output permeate stream at a recovery rate substantially equal to a second target recovery rate during a second period of time which exceeds the maximum non-scaling recovery rate for the at least one filter membrane and the first target recovery rate, wherein the at least one filter membrane is not flushed between the steps of causing the first driving signal and causing the second driving signal.
2 . The method of claim 1 , wherein causing the one or plurality of antiscalant doses to be provided to the at least one filter membrane includes introducing a plurality of antiscalant doses.
3 . The method of claim 1 , wherein determining when the predetermined moment will occur is based on a quality measurement of the output permeate stream.
4 . The method of claim 1 , wherein the pre-antiscalant maximum non-scaling recovery state is detected prior to reaching the maximum non-scaling recovery state.
5 . The method of claim 1 wherein determining when the predetermined moment will occur is based on a constant duration of time.
6 . The method of claim 1 wherein determining when the predetermined moment will occur is based on a concentration of antiscalant within the at least one feed stream.
7 . The method of claim 4 , further comprising a first induction period and a second induction period, the second induction period occurring after the first induction period, the first induction period ending when the pre-antiscalant maximum non-scaling recovery state is reached and the second induction period extending from when the one or plurality of antiscalant doses are provided to the at least one filter membrane to when the post-antiscalant maximum non-scaling recovery state is reached.
8 . The method of claim 7 , wherein the second induction period is equal to or longer than the first induction period.
9 . The method of claim 7 , wherein the second induction period has an overall duration that is at least half an overall duration of the first induction period.
10 . The method of claim 1 , wherein causing the first driving signal to be provided to the at least one pump exerts a pressure of 90-120 bar on the at least one filter membrane.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of International Application No. PCT/US20/34674 filed on May 27, 2020 under 35 U.S.C. 120, which claims the benefit of U.S. Provisional Patent Application Ser. No. 62/991,393, filed on Mar. 18, 2020, each of which is fully incorporated herein by reference. TECHNICAL FIELD This specification relates to filtration systems and managing scale formation within the same. BACKGROUND INFORMATION Water filtration systems often include at least one filter membrane for producing permeate from a feed stream. One approach to water filtration utilizes a steady-state continuous reverse osmosis (RO) operation/cycle and a pump that displaces feed through one or more filter membranes at a substantially constant pressure. The proportion of feed exiting as permeate relative to the portion of the feed exiting as retentate/reject establishes the recovery rate for the system. Such continuous flow systems typically operate at a recovery rate that is at or below a rate at which scaling conditions are induced. Consequently, continuous flow systems have a relatively low maximum recovery rate, e.g., 50-75%, to avoid formation of scale and fouling. Another approach to water filtration utilizes a batch RO operation/cycle. In batch RO a pump varies pressure over time to overcome the osmotic pressure of one or more filter membrane(s). While batch RO systems enable a relatively higher rate of recovery relative to continuous flow systems, such systems must be periodically flushed to maintain permeate flux. BRIEF DESCRIPTION OF THE DRAWINGS Various aspects and features of the present disclosure will be better understood by reading the following detailed description, taken together with the drawings wherein: The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the teaching of the present specification and are not intended to limit the scope of what is taught in any way. FIG. 1 shows an example diagram of a filtration system continuum having opposite extremes representing continuous RO and batch RO operations, respectively. FIG. 2A shows a block diagram of an example filter configuration for use during continuous RO operations. FIG. 2B shows a block diagram of an example filter configuration for use during batch RO operations. FIG. 3 shows a block diagram of an example filter system in accordance with embodiments of the present disclosure. FIG. 4 shows a plurality of example filter operation sequences for execution by the filter system of FIG. 3, in accordance with embodiments of the present disclosure. FIG. 5 shows an example process for performing one or more filter operation sequences of FIG. 4 in accordance with embodiments of the present disclosure. FIG. 6 shows an example process for generating first and second induction periods to extend operation of the filter system of FIG. 3 when operating at a recovery rate above a non-scaling rate in accordance with an embodiment. FIG. 7 is a graph illustrating various recovery target rates of the filter system of FIG. 3 over time (T) when executing one or more filter operation sequences in accordance with embodiments of the present disclosure. FIG. 8 is another graph illustrating various recovery target rates of the filter system of FIG. 3 over time (T) when executing one or more filter operation sequences in accordance with embodiments of the present disclosure. DETAILED DESCRIPTION RO-based filtration systems continue to increase in popularity and adoption, particularly in commercial and large-scale filtering plants. RO-based water filtration systems fall into one of two modes of operation, namely continuous RO or batch RO. Although both modes of RO filter systems utilize similar filter technology, such as NF, Sea water RO and brackish water RO technology, filter systems that implement continuous RO operation versus those that implement batch RO operation fall at opposite ends of a continuum relative to each other. This continuum may better be understood by way of illustration. FIG. 1 shows one such example continuum having continuous RO and batch RO operations falling at opposite ends/extremes. In particular, continuous RO systems operate at relatively low recovery rate to achieve a non-scaling steady state (with or without antiscalant) with operational times being measured in weeks to months. On the other hand, batch RO systems operate at recovery rate that is above a non-scaling steady state, i.e., 100% recovery, with operational times being generally a fraction of the amount of time continuous RO systems operate before filter membranes get flushed, e.g., via feed. For instance, some batch RO operations occur for as little as a few minutes to several hours before a flush cycle occurs. Continuous RO systems feature various structural and operational differences relative to batch RO systems. New and existing filter designs implement batch RO when high recovery is