Chapter VI. Conclusions and recommendations
2. Recommendations
Biological wastewater treatment recently started to be used in many developing regions.
Wastewater treatment plants constructed today aim to reduce the concentration of pollutants to an acceptable level but usually require high investment costs, skilled labour and consume a lot of energy.
Biological wastewater treatment offers major advantages over alternative treatment strategies:
low operation and maintenance costs, efficient removal of organic compounds, easy operation and improved flexibility. However, the method requires large set up space and long residence times, which additionally often changes due to changes in physical conditions such as temperature, pH, etc. To reach good removal efficiency and maintain a stable state, the biological wastewater treatment needs to include other options such as growth rate, light intensity and aeration surface.
Firstly, the results proved that temperature and light conditions are the most important factors to keep algae growing and to maintain their removal capacities, especially for ammonia nitrogen. Therefore in future experiments, a variation of these factors should be examined in more details.
Secondly, it appears that the results of the algal ammonia removal efficiency in the light/dark phases do not show an unequivocal difference. Further research must be considered to get wider data about its effects.
Thirdly, the results show that a large amount of organic nitrogen accumulated in the algal sludge. Methods to store the algal sludge are necessary to recycle nutrients as well as for producing biogas and fertilizer. Future research may be needed to measure the amount of biogas producible from the algal sludge.
Fourthly, the application of a recycling line in the baffled algal reactors has proven to provide a high removal efficiency by recycling the residual degraded substances. Further researches should focus on the ratio of the recycle flow and its effects.
Fifthly, application of baffles in algal wastewater stabilisation ponds can improve its treatment effects. To obtain highest removal efficiency by the use of algae in the pre-settled wastewater, pond designers should consider a depth of the pond around 60-100cm. Use of algae as a promising biofuel should be taken in to account.
Sixthly, the transform matrix model must be based on many biological process-chains and variables to properly model the algal development. In this study, those parameters have been mostly taken from the literature. Therefore, the output of the model does not completely represent the reality of the examined algal system.
To better understand the biological processes in the reactors, those parameters should be collected from the practical results, such as the autotrophic growth, autotrophic biomass, decay rate and growth of algae on nitrates. In addition, the algal model to predict the nitrogen removal via biological processes still requires some modifications to properly model algal nitrogen removal with ASM1 and 3. Therefore, further studies focusing on this issue should be considered.
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