This paper attempts to identify the cause of silica polymerization during formation of calcium phosphate scales at elevated pH, and investigates methods to inhibit this co?precipitation even when ferric ions are present in the feedwater of wastewater RO systems....

This paper details the requirement to understand the water quality characteristic of the feed and the filtrate requirement. It talks to the addition of pretreatment chemistry to prevent scaling and fouling without adversely impacting product water quality....

This PowerPoint reviews chemical treatment options for Membrane treatment plants with an emphasis on opportunities in Texas....

This presentation includes an overview of RO membrane fouling and scaling. It discusses biological, particulate, and inorganic fouling mechanisms and the chemistry driving scaling, antiscalant performance, and membrane cleaning. Complex interactions are discussed, including calcium bridging, chelating, and surfactant behavior....

Corrosion coupon studies were performed on the finished water of various plants on the East Coast of Florida. Of those plants, three produced finished water consisting of Reverse Osmosis (RO) permeate blended with filtered feedwater, one plant blended RO permeate with lime softened water, and one plant produced only lime softened water. The purpos...

This paper investigates the types of silica fouling that would occur in the presence of aluminum carryover from coagulant dosing and evaluates multiple types of antiscalants to determine if such fouling can be prevented....

This presentation from a preconference workshop in 2014 for Back to Basics on membrane technology discusses pretreatment chemistry for microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Water chemistry is presented and it's influence on the membrane treatment methods....

A 6 MGD reverse osmosis plant in South Texas that was using chlorine to oxidize arsenic for improved membrane rejection was experiencing severe membrane fouling. The ferrous ions in the well water were being oxidized by the chlorine, resulting in ferric hydroxide fouling of the cartridge filters and membranes throughout the system. Despite numerous...

Provdes a detailed overview of membrane pretreatment chemistry design considerations. Includes sections on coagulation and antiscale chemistry....

This paper describes a new silica scale prediction model and emphasizes the importance of considering cation species and concentrations in any membrane scaling projection. Two case studies are presented, each of which had been used to validate the new silica scaling model and the silica kinetics index....

This paper describes the development and validation of arsenic rejection computer using reverse osmosis ( RO) and/or nanofiltration(NF)....

This paper discusses certain aspects of iron behavior, the developed computer model, and its application and validation using a pilot system at the Florida RO plant. Speciating the hydrolysis states of ferric iron with respect to pH, ionic strength, and temperature, is essential to predicting the concentration factor as well as the scaling potentia...

Innovations in antiscalant technology have allowed for improved scale control under more severe conditions. This presentation discusses the application of a high performance antiscalant for calcium carboante inhibition at a plant in South Florida....

This presentation discusses different cleaning chemicals and techniques. It explains the chemistry of membrane cleaning, and how chemicals interact with different foulants under different conditions....

The purpose of this work was to identify a method for determining maximum recoveries in RO systems where calcium carbonate was a concern, and to find a reliable method for antiscalant dosage prediction....

This paper attempts to identify the mechanisms by which chlorine dioxide aided in foulant removal, and to verify the tolerance of polyamide membranes to ClO2 as a cleaning aid....

This presentation review the relationship between membrane properties including Surface area and flux and permeability. Salt rejection of various elements and testing procedures is reviewed as is the rejection of non-ionized molecules. Comparing membrane specification sheets is discussed and some recommendations on improving membrane operations is ...

The Torrance Desalter could not be commissioned after a two year expansion because of increases in interstage feed pressure to the 2nd stage. The initial assumption was that scaling was occurring. However, an autopsy and cleaning study determined that the foulant was entirely organic in nature. The approach was to mitigate the problem by resolving ...

A municipality in Texas had been operating its new reverse osmosis (RO) trains for only a few months when it started experiencing severe decline in flux and an increase in salt passage. Membrane cleaning did not restore performance. Cartridge filter analysis found heavy iron loading. Membrane autopsies revealed heavy iron hydroxide fouling across t...

A municipality in Texas had been operating its new reverse osmosis (RO) trains for only a few months when it started experiencing severe decline in flux and an increase in salt passage. Membrane cleaning did not restore performance. Cartridge filter analysis found heavy iron loading. Membrane autopsies revealed heavy iron hydroxide fouling across t...

Concentrate pH in RO and NF applications plays a significant role in the formation of certain scales and the rejection of various contaminants. Incorrectly predicting pH can lead to excessive chemical costs or operational issues. Likewise, permeate pH is of utmost importance for determining post-treatment requirements for the product water. Most me...

Concentrate pH in RO and NF applications plays a significant role in the formation of certain scales and the rejection of various contaminants. Incorrectly predicting pH can lead to excessive chemical costs or operational issues. Likewise, permeate pH is of utmost importance for determining post-treatment requirements for the product water. Most me...

The use of chloramines has become a standard pretreatment method for biofouling control in water reuse RO. When used in the 2 - 3 ppm range, chloramines have been known to cause only minimal losses in salt rejection, and the benefits are generally believed to far outweigh the risks. However, in recent years, significant irreversible declines in per...

The use of chloramines has become a standard pretreatment method for biofouling control in water reuse RO. When used in the 2 - 3 ppm range, chloramines have been known to cause only minimal losses in salt rejection, and the benefits are generally believed to far outweigh the risks. However, in recent years, significant irreversible declines in per...

Concentrate pH in RO and NF applications plays a significant role in the formation of certain scales and the rejection of various contaminants. Incorrectly predicting pH can lead to excessive chemical costs or operational issues. Likewise, permeate pH is of utmost importance for determining post-treatment requirements for the product water. Most me...

Concentrate pH in RO and NF applications plays a significant role in the formation of certain scales and the rejection of various contaminants. Incorrectly predicting pH can lead to excessive chemical costs or operational issues. Likewise, permeate pH is of utmost importance for determining post-treatment requirements for the product water. Most me...

...