Aerobic Treatment for recycling kitchen wastewater

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WORLD POPULATION is at the verge of water shortage which demands proper management of water resources to meet requirements of rapidly growing population. Collection and reuse of wastewater has never been a priority in Pakistan but the concept is much more demanding in current needs especially in the areas having water shortage like Pothowar region. A low cost treatment system to reuse wastewater in agriculture sector may also aid in meeting water shortages.

Wastewater creates public health problems by polluting natural water resources, and may also affect agriculture production. Treatment of wastewater could have positive impact on environmental health by reducing pollution, and to some extent help to mitigate water scarcity problems in agriculture sector. Recycled wastewater may be used for irrigation of garden, parks and road sided plantation; and thus may enhance urban amenities. Grey water (GW) is a type of wastewater from urban areas including water from showers, washing machines, kitchens sinks etc. According to studies, a single person generates approximately 30-70,000 liters grey water per year. Proper recycling of GW can make it a good source of water supply for a variety of purposes, including irrigation. This can also lead to a considerable reduced water demand.

Wastewater treatment has gained importance worldwide, but there is an immense need to develop a low cost treatment system for recycling grey water from urban areas including water from showers, washing activities and kitchens etc. which can be used in agriculture sector. Most people consider bacteria and other microorganisms to be undesirable components of wastewater. In fact, only a small fraction of the microbes found in wastewater are truly pathogenic. Naturally occurring microorganisms are the workhorses of wastewater treatment. Consisting of bacteria, fungi, protozoa, rotifers and other microbes, these organisms thrive on many of the complex compounds contained in domestic wastewater. Different technologies have been employed for grey water treatment; some are natural, other employ physiochemical and biological processes but choice for adopting proper technique depends upon multiple factors. Major focus of all such treatment processes should be on the need of low cost treatment systems to improve the water quality.

An aerobic treatment system (ATS) is a small scale sewage treatment system similar to a septic tank system that uses an aerobic process for digestion rather than just the anaerobic process used in septic systems. The traditional septic system, the aerobic treatment system produces a high quality secondary effluent, which can be sterilized and used for surface irrigation. Aerobic wastewater treatment encourages the growth of naturally-occurring aerobic microorganisms as a mean of renovating wastewater. Such microbes are the engines of wastewater treatment plants. Organic compounds found in waste water are high-energy forms of carbon that power these engines. Domestic waste water is a source of about 47 per cent organic material, which can promote growth of microorganism being a source of energy for them. Microbial treatment of wastewater is thus an effective way to degrade organic compounds.

Currently, a study has conducted at Attock Refinery Limited (ARL) Rawalpindi, in which a system has designed for recycling kitchen wastewater under aerobic conditions utilizing activated sludge. Pre and post-treatment water quality parameters were measured to compare the efficiency of system to reduced pollutants in kitchen wastewater. Emphasis was the reuse of kitchen grey water with a simple and cost effective water recycling system that could be employed locally to make recycled water suitable for irrigation application, which may be an important step towards the sustainability of an urban ecosystem. This experiment was conducted at ARL Rawalpindi by employing aerobic treatment of wastewater originating from the kitchen collected into primary settling pit of the treatment system. Screening was done within secondary settling pit having storage capacity up to 10,000 liters. A water pump was installed at settling pit to pump out the water into the main biological treatment tank containing activated sludge. These bacteria grew naturally and are responsible for decomposition of suspended/ dissolved organic matter.

Sampling of kitchen wastewater was done from settling pit (untreated) and storage tank (treated), fortnightly for three months. From each level samples were collected and analyzed in Quality Control Laboratory of ARL to monitor the selected water quality parameters. The quality of treated kitchen wastewater was analyzed for physiochemical parameters including pH, BOD, COD, EC, turbidity, TSS, TDS and oil contents.

This treatment resulted in remarkable improvement in wastewater quality and significant differences were recorded between kitchen water and coagulation tank outlet water quality which showed that wastewater quality was improved to a significant extent. There was significant decrease in concentration of pollutants between wastewater from kitchen waste outlet source and sample taken after aerobic treatment. The results clearly showed better efficiency of aerobic treatment system that reduced the values of the above mentioned parameters up to 87% and enabled it to be fit for irrigation purposes.

Aerobic treatment units can provide rapid treatment of waste water and can be replicated to provide high quality effluent in situations where the natural surrounding has limited ability to renovate domestic wastewater and in the areas having water scarcity.


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