Effects of some functional parameters on do deficit in a natural stream

The effects of variation of stream velocity, distance, ultimate biological oxygen demand BOD, on initial dissolved oxygen DO and optimum dissolved oxygen DO deficit, in Amadi creek was studied Amadi creek, located in Port- Harcourt metropolis is a unique CREEK that is of high economic importance to the residents ofRumuobiakani, Mini-Ewa, Oginigba, Woji and Okujagu communities as it hosts the activities of the majority of the companies around theTrans- Amadi Industrial area and also provides water for fishing and water transportation The study was carried out to evaluate the waterquality changes resulting from increasing human and industrial activities in and around the creek A point-source waste waterdischarge with flow rate Q), biological oxygen demand BOD and dissolved oxygen demand DO), of 0.000018m3/s,1000mg/l, and mg4.1 formed the first case The other case contained an additionalpoint source with flow rate (Q), biological oxygen demand (BOD), and dissolved oxygen demand DO) of 0.000035m3/s,500mg/land4mg/l respectively The study of the DO resources of the stream was undertaken with the aim of providing concepts which can be ofassistance to regulatory agencies responsible for making decisions for water quality management The DO deficit equations are solved bythe methods of simple calculus classical optimization), which simplifies the mathematical solution of the model equations byavoiding difficult to evaluate integrals Two scenarios were identified and used to investigate the effect of BOD on the DO level in the stream, using mathematical simulation techniques Simulation results of the two scenarios suggest that the dissolved oxygen DO deficit isdepends mainly on the distance between waste discharge pointsHence to ensure minimum impact on water quality waste discharge locaEons should be placed at the opEmal locaEons of mand !! m upstream and downstream waste discharge points respecEvely, at an opEmum DO deDcit of mg#l for the Drstscenario, and at m, !! m, !m upstream and downstream waste discharge points respectively for the secondscenario at an opEmum DO deDcit of mg#l A characteristc DO curve shows the DO deficit increasing as the BOD in the waste wateris being degraded,while the DO deficit decreases as the BOD consumption rate becomes smaller than the reaeration rate, as the waste stream flows downstream Generally as stream velocityincreases, the reaeration coefficient increases, resulting in an increased rate of oxygen transfer between water and theatmosphere, and hence an increase in the DO deficit initially, followed by a gradual decrease further downstream The ultimateBOD deceases progressively as the waste stream moves downstream It is recommended that if a new waste input is proposed for a streamboth its BOD input and the proposed location with respect to the other functional parameters are important in order to determine the effects on the creeks dissolved oxygen DO level