Longterm experience in the use of polymeric coagulants at Umgeni Water

Abstract

Umgeni Water, the bulk treatment authority for the cities of Durban and Pietermaritzburg changed from inorganic coagulants to synthetic polymeric coagulants at its various works in the mid 1980s. The advantages and disadvantages experienced with the new chemicals are discussed in detail in the paper and the changes to test procedures necessary are highlighted. The polymeric coagulants were found to produce good quality water in line with international norms but their unsuitability for enhanced coagulation may preclude their use on some of the works where organic enrichment is becoming a problem.

Review on Chemical treatment of Industrial Waste Water

“…Lower coagulant dose requirements, a smaller volume of sludge, a smaller increase in the ionic load of the treated water, reduced level of aluminum in treated water, Cost savings of up to 25-30% (Wakeman and Tarleton, 1999;Nozaic et al, 2001) Polyelectrolytes act in two distinct ways: charge neutralization and bridging between particles. Because wastewater particles are normally charged negatively, low molecular weight, cationic polyelectrolytes can act as a coagulant that neutralizes or reduces the negative charge of the particles, similar to the effect of alum or ferric chloride.…”

The heterogeneous coagulation and flocculation of brewery wastewater using carbon nanotubes

“…After this time period, the stirrer was withdrawn and the floc was allowed to settle for a specified time of 30 minutes. However, since no flocs were visible due to poor dispersivity of CNTs, the treated water was filtered through a 9 Whatman # 1 equivalent paper and the parameters of the filtered water measured as an indication of coagulation (Nozaic et al, 2001). The parameters analysed were turbidity and chemical oxygen demand (COD).…”

A new cation‐modified Al‐polyacrylamide flocculant for solid–liquid separation in waste drilling fluid

“…Compared with inorganic flocculants, polymer flocculants offer the following advantages when used in waste water treatment: lower coagulant dose requirements, a smaller volume of sludge, a smaller increase in the ionic load of the treated water, and cost savings of up to 30%. 3,4 The flocculation efficiency of polyacrylamides (PAMs) is determined by several factors including the molecular weight and charge density of the polyelectrolytes, the pH and ionic strength of the suspending medium, the size and surface charge of the dispersed particles, and the adsorption density and conformation of the absorbed flocculants. [5][6][7][8][9][10] These properties can be modified by the nature and proportions of the monomers; therefore, several kinds of PAMs can be prepared.…”

“…These polymers are made by the combination of acrylamide monomer with other kinds of monomers, such as acrylates, 11,12 carboxymethyl tamarind, 13 and dicyandiamide. 14 Compared with these polymer flocculants, the inorganic-organic composite flocculant, such as Al(OH) 3 -polyacrylamide, was found to be more effective in solid-liquid separation, 15 this is mainly because of the star-like structure of the flocculant to improve the flocculation performance and to form the pellet like floccules. Zeng et al 16 prepared a composite chitosan flocculant by chitosan, polyaluminum chloride (PAC), and silicate, and compared with PAC, the percentage of removing COD (organic contaminant), SS (solid suspending substances), and Al 31 in the treated water using this composite chitosan flocculant was enhanced by 1.8-23.7%, 50%, and 61.2-85.5%.…”

“…Many inorganic and organic polymer flocculants have been used to flocculate the suspended solids in the waste drilling fluids, but the effect is not good. The objective of this work was to prepare a cationmodified Al(OH) 3 -polyacrylamide copolymer (CAPAM) and to examine its flocculation performance in waste drilling fluids. This flocculant was prepared by in situ polymerization in our laboratory.…”