Sanitizing Waste Water from 12 MW Rice Hull Fired Power Plant by Functional Compound Agents
Abstract
Wastewater (WW) produced by a 12 MW Rice Hull Fired Power Plant was analysed and then treated with organic based functional compound agents (FCA) to determine its sanitizing efficacy. Composite samples were analysed for Silica (SiO , Nitrates (NO -), Biological Oxygen Demand (BOD), Total Suspended Solids (TSS) and heavy metals specifically lead 2) 3 (Pb) and mercury (Hg) concentration. In-situ properties, namely; pH, temperature, and dissolved oxygen (DO) were also determined by grab sampling. Correlation of these properties with other parameters was done as well. Results were compared with the permissible level of the country’senvironmental regulating body. Exceeding the permissible limit of Class C surface water based on the environmental regulating agency were Pb, temperature, DO, and BOD indicating that the water is slightly unfit for irrigation purposes. Treating the WW (p <0.05) with the FCA resulted in the reduction of pH by 4.6%, in high increase of TSS by 3,315.64% and increase of Pb by 239.62%. Meanwhile, no change was observed in the temperature, DO, NO-SiO and Hg. Therefore, the FCA tested had no sanitizing effect on the WW. 3, 2
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Introduction
Wastewater is produced from rice hull fired power plant which could generate electricity. Water treatment reject, cooling tower blown down, boiler, rain water, cleaning of vehicles and domestic waste are considered as the sources of effluent. Production of steam is an important component of any biomass fired power plant which requires water extracted from deep well ground water. This is done using submersible pump made possible by boring holes to reach the water source. This water resource is often high in mineral content [1] and is treated before using for steam production. Hence, minerals and ions in water must be removed to prevent corrosion of pipes.
Wastewater comes from rejected water during the process of regeneration and cleaning of water treatment plant [2]. Untreated or improperly treated wastewaters are the major sources of surface water body pollution especially when it contains sediments or fly ash. It is one of the most serious environmental problems resulting from industrial, domestic and agricultural activities [3]. Wastewater contaminated with even low concentration of heavy metals or other pollutants may affect the quality of soil, plants, aquatic life and human health. These metals affect soil quality by decreasing microbial processes or activities and may inhibit the physiological metabolism of plants.
Consequently, this condition could become potential threat to human and animal health because of the subsequent accumulation of heavy metals in the food chain [4]. Through the years, series of expensive chemical based treatment technologies have been developed for wastewaters but there is a dearth in the use of non-chemical and organic based treatment strategies. As such, this investigation explored the use of FCA to sanitize wastewater from a 12 MW Rice Hull Gasifier Plant in the Philippines.
FCA was constituted using the following: 7 bacteria for decomposition, enzyme production and nutrient transformation; 3 bacteria for decomposition of polysaccharides and enzyme production; 3 bacteria for enhanced decomposition, compost “Sweetening” and probiotics production; 5 bacteria for nitrogen fixation; 7 fungi composting microbes; aerobic and unaerobic methane producing bacteria; sulfate and ammonia consuming and heavy metal binding bacteria and emulsifiers.
Conclusion
The FCA was effective in reducing the pH and dissolved oxygen level while inefficient in reducing the temperature level, amount of BOD, TSS, silica, nitrate, lead and mercury. The possible increase in heavy metals in the wastewater, particularly “lead”, could have been due to the proximity of the rice hull fired plant (being adjacent) to a paddy field where inorganic fertilizers and insecticides are being applied. The rice hull gasifier fired plant continuously extract groundwater that serves as cooling agent and can be reprocessed to be apart of the wastewater.
Nevertheless, these results can serve as precautionary measure to minimize the potential risk to the environment. The apparently alarming concentration of pollutants, particularly the heavy metals, could result in the deterioration of nutrient soil quality and bio-accumulation by the plants thereby rendering serious environmental problems.
Moreover, the wastewater quality parameters documented may serve as benchmark data in predicting the cumulative toxicity it would bring to nearby vegetation over a certain period, through algorithm equations. More research efforts should therefore be done on other similar or modified FCA to make it an effective sanitizing agent for wastewater from Rice Hull Fired Power plants considering their growing use globally and long term adverse effects to the environment, humans, and animals.
