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Heated Aluminum Oxide Parties (HAOPs) for the Replacement of Coagulation Chemicals in Water Treatment

Technology Overview

Membrane-based separation technology has been widely used for various water treatments. However, because of the nature of filtration, contaminants that are removed by the membrane tend to deposit on the membrane surface, resulting in pore blocking and permeate flux reduction. This phenomenon, referred to as membrane fouling, occurs in almost all membrane processes. Various strategies have been developed to tackle the issue, including pretreatment of raw source waters by coagulation.

Compared with conventional adsorbents and coagulants, heated aluminum oxide particles (HAOPs) have been found to be more effective in organic matter removal for various source waters including surface water, seawater and effluents from membrane bioreactor (MBR). As a result, raw water pretreatment using HAOPs can mitigate organic fouling in subsequent membrane processes significantly. Furthermore, the sludge generated during the pre-treatment using HAOPs is far easier to dewater than that generated using conventional coagulants, saving the costs both in the dewatering step and the subsequent sludge transport and disposal steps. Finally, HAOPs-based treatment is much more robust and reliable than the conventional coagulation-based processes under conditions of fluctuating influent composition.

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Technology Features & Specifications

Fouling mitigation is essential in all membrane processes to keep energy costs reasonable and to prolong membrane lifespan. Recent work has shown that heated aluminum oxide particles (HAOPs) are highly effective in mitigating the rate and extent of membrane fouling by both natural organic matter (NOM) and particulates in water treatment applications, using both fresh and salty water as feed; they are also effective in removing both effluent organic matter and phosphorus from treated wastewater. The process is carried out using a cyclic three-stage protocol comprising: (i) deposition of HAOPs on a conventional membrane; (ii) filtration of feed water; and (iii) de-coating the HAOPs layer. The coating layer acts as a secondary membrane which prevents fouling of the primary membrane by adsorbing organics and colloidal particles in the feed and it also can be easily removed from the primary membrane surface by backwashing, then re-deposited in-situ without the need to take apart the membrane module. Therefore, the HAOPs coating layer is also considered as a pre-deposited dynamic membrane.

Potential Applications

  • In water treatment industry, heated aluminum oxide particles (HAOPs) coated membrane offers a far more efficient pre-treatment process for membrane fouling mitigation. In the treatment process, MBR effluent is treated by passage through micron-sized adsorbent particles (HAOPs) packed in a layer that is <1mm thick. The process removed 52% of the organic matter (for an MBR effluent) and the sludge generated by the process was easy to dewater and dried. This pretreatment step removes enough foulant to allow a downstream UF membrane to operate at significantly higher fluxes than when conventional pretreatment is applied. 
  • An innovative water treatment technology for customers with high requirement for phosphorus removal (99.9% of phosphorus removal can be achieved using HAOPs coated membranes, where the phosphorus concentration in the feed ranged from 4-9 mg/L).
  • Pre-treatment with HAOPs coated membrane also reduced the formation of chlorinated and brominated trihalomethanes by more than 67% and of haloacetic acids by 64-88% in simulated distribution system tests.

Customer Benefits

By applying this technology,

  • The membrane-based water treatment process can be significantly improved due to the prolonged lifespan of the membranes.
  • Huge cost savings can be achieved in both the sludge dewatering step and the subsequent sludge transport/disposal step.
  • A more efficient and cost-effective water treatment technology for phosphorus removal.

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