BY
Datuk IR. Abdul Kadir Mohd Din
Chief Executive Officer,
Indah Water Konsortium Sdn. Bhd.

Historically, the first thought of sewage treatment dates back to the end of 18th Century when septic tanks were introduced in the West. By the nineteenth century sewage treatment methods developed rapidly to meet the needs of basic sanitation. Today, modern and sophisticated treatment technologies are continuously developed for the purpose of protection of environmental quality in a cost efficient manner. The key driver for this trend is the increasing need for a more sustainable long term solution in terms of both the economics and the environment. In this regard, the current practice in safe disposal of end products from sewage treatment namely, the effluent and sewage sludge, will no longer be able to meet the complex environmental challenges of climate and water sensitive futures. For this, the sewage treatment industry needs to be transformed into a resource harvesting industry. This paper describes the paradigm shift from traditional basic treatment to potential new business model via resource recovery in the sewerage sector. The key idea is utilizing the ‘Green Technology’ and ‘Zero Waste Concept’ to transform the sewerage industry into a sustainable and economically attractive model.

The typical treatment process flow for a modern mechanized activated sludge plant is depicted in Figure 1.

Basically it involves 2 main components namely: (i) Pre-treatment for grit and grease removal; (ii) Main treatment process units where the major organic and solids pollutants are removed via Biological process (ie. secondary treatment). The secondary treatment process involves a reactor or tank for biological breakdown of organic pollutant by native sewage microbes (i.e. MLSS). This basic secondary treatment technology produces clear effluent that can be discharged into the environment, whilst the waste sludge (WAS) is typically stabilized and dewatered into semisolid form (at 15-20% dry solid content; also known as biosolids) for disposal to landfills. If the stabilization process is involved, there is anaerobic sludge digestion and biogas is produced as well.

More recently technologies are focused on enhancing nutrient removal namely nitrogen and phosphorus as well as in reducing the operating energy requirement of systems as well as smaller foot print. The latest being a variation of Sequencing Batch Reactors, Moving Bed Bioreactor, Membrane Bioreactor, Combination of Anaerobic UASB (Upflow Anaerobic Sludge Blanket) and Aerobic systems. Although these developments produces high quality treated effluent, the waste by-products remains typically disposed unto the receiving environment.

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