Development of a model to be used as an indicator of oily wastewater pollution, fingerprinting and compliance using dimensional analysis

Abstract

Water is the source of life because all living organisms cannot survive without it and it is the most important liquid in the ecosystem hence protecting water resources and ensuring water quality should always be an issue of the highest priority at the top of all environmental issues. Currently, both developing and developed countries are experiencing numerous water quality challenges. Among the challenges include lack of adequate water due to pollution as well as the management and disposal of oily wastewater effluents in water resources. Regarding the issue of pollution due to oily wastewater, the current trend shows that, with the increase in industrialization, the amount of oil used is also increasing, thus causing more stress in terms of management and treatment of wastewater. Oily wastewater pollution has mainly been reported to cause hazardous effects to both organisms and the environment by causing the deterioration of aquatic resources. This in-turn affect the quality of ground water, surface water, endanger human health, cause of atmospheric pollution, destroy/degrade natural landscape, and even cause safety issues due to the use of coalescence of the oil burner that arise. Due to this phenomena, various regulatory bodies have established some guidelines to regulate the disposal of oily wastewater that is discharged to the environment. Therefore, oily wastewater needs to be treated prior to being discharged into the environment to comply with state and local disposal regulations. Industries and companies that deal with activities that lead to the discharge of oily wastewater need to comply to the enforced regulations to ensure that the characteristic of their effluents meet the stipulated disposal criteria. The effluent quality requirements for discharge of oily wastewater to the municipal streams are determined by local and municipal authorities and, they may vary from place to place. This dissertation focused on the development of a model that can be used to indicate the quality of oily wastewater known as oil -produced water (OPW) which is normally discharged by petroleum industries to into receiving water bodies. The model development was accomplished by using a measure of evaporation patterns in relation to certain environmental and climatic variables. This is possible because certain physico-chemical parameters that normally characterize OPW are known to have a direct relationship with the rate and pattern of OPW evaporation. However, due to the complexity of the relationship between the parameters being measured, it was imperative to employ dimensional analysis approach that is based on Buckingham pi () theorem for the estimation of oil produced water evaporation (OPWE) as a function of clear water evaporation (CWE) and influencing parameters. The parameters that were investigated in this project includes climatic and environmental parameters. The climatic parameters included wind speed (W), solar radiation (R) and air temperature (Ta). The environmental parameters were: oil produced temperature (Topw), electric conductivity (EC), total dissolved solids (TDS), biochemical oxygen demand (BOD), total suspended solids (TSS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total petroleum hydrocarbons (TPH) and total organic carbon (TOC). The results have indicated that, the physico-chemical analysis for the samples from the oil depot (petroleum industry) were found to be within acceptable threshold limits except for COD, TPH and EC that slightly surpassed. These findings and observations from this work suggests that, wastewater from this oil depot that was studied should not be directly discharged into municipal channels, rivers, and streams unless it undergoes secondary and tertiary treatment processes. Alternatively, the wastewater may arrange for an agreement with the municipals to allow for their effluents to be channelled to local municipality streams where they will undergo further treatment since most depot do not have appropriate facilities for post-treatment process. This is because, the chemical effluent must also adhere to the guidelines and regulations of the municipal where the wastewater will be channelled into. Since most depots are not equipped with appropriate facilities to check for compliance prior to the discharge of the effluents, this work has developed a multiplicative model for such purposes. Nonetheless, modelling the OPWE for compliance purposes has received little attention thus far. Driven by this knowledge gap, this project focused on the development of a model to predict the compliance of OPW effluents for both checking of quality and attaining the regulatory compliance. The modeling approach was based on experimental data collected on the oil depot, South Africa for a period of six months. As a result of this analysis, a multiplicative model to formulate OPWE as a function of influencing parameters indicated a reasonably well accuracy (RMSE = 0.49) for the OPWE estimation. The evaporation and correlation study supported the hypothesis. As shown by the evaporation patterns that most of the time the effluent was compliant to the guidelines mostly during winter time than summer time, and this observation was explained by the evaporation patterns that in summer when there is more solar radiation, the wastewater absorbed more heat and enhanced the evaporation rates which is directly related to both environmental and climatic parameters. Furthermore, the model developed by this work, can be used for fingerprinting since OPWE from different processes may have similar chemical composition but in different levels and ratios. This can be exploited to differentiate them using the same developed model as the coefficients pattern tend to be characteristic to a certain OPWE and the model can then be used to fingerprint and identify culprits in case of discrepancies.