Rehabilitation of Aisleby 3 waste wa­ter sta­tion

Chronicle (Zimbabwe) - - Business - Yoliswa Dube

THE rehabilitation and com­mis­sion­ing of the plant and equip­ment at Aisleby 3 waste wa­ter sta­tion will im­prove real time mon­i­tor­ing of in­flu­ent and ef­flu­ent, mak­ing it eas­ier for plant op­er­a­tors to vary plant pa­ram­e­ters ac­cord­ing to the load­ing of the plant, an of­fi­cial has said.

Bu­l­awayo City Coun­cil deputy di­rec­tor of en­gi­neer­ing ser­vices En­gi­neer Mente Ndlovu said the plant is a Bio-Nutri­ent Re­moval Plant (BNR) mean­ing it uses bi­o­log­i­cal or­gan­isms or bac­te­ria to re­move nu­tri­ents such as phos­pho­rous and ni­trates, which are haz­ardous to the en­vi­ron­ment.

This plant re­ceives sewage from Queens Park West, Ma­hat­shula North and South, Glengary, Khu­malo, Park­lands, Sel­bourne Park, Wood­lands and parts of Hill­side.

“The rehabilitation of the out­fall sew­ers will fa­cil­i­tate in­flows of up to 7.5ML a day at Aisleby 3 and add an­other 10ML to Aisleby 1 and 2. The deep sec­tion at Sauer­stown is ex­pected to be com­mis­sioned end of Novem­ber.

“The ten­der for rehabilitation of Aisleby 1 and 2 is at ad­ju­di­ca­tion stage and we ex­pect works to be com­mis­sioned around June 2017,” said En­gi­neer Ndlovu.

Real time mon­i­tor­ing of pro­cesses data such as process in­flows and out­flows, mo­tor run hours and lev­els of dis­solved oxy­gen are pos­si­ble through a Pro­grammable Logic Con­troller (PLC) and a lo­cal Wi-Fi network that has been setup at the plant.

“We are work­ing on ex­pand­ing this network to our Tower Block of­fices so that we can also mon­i­tor the plant from the com­fort of our of­fices.

“The bio-re­ac­tor aer­a­tors have been au­to­mated to re­spond to lev­els of dis­solved oxy­gen, the main vari­able in the bio-re­ac­tor process.

“This au­to­ma­tion will re­sult in en­ergy sav­ings in that the aer­a­tors will only run when dis­solved oxy­gen lev­els are crit­i­cally low,” said En­gi­neer Ndlovu.

He said through this network, it is also pos­si­ble to an­a­lyse trends on the per­for­mance of the plant over time so as to fine tune its set­tings.

“It makes it eas­ier to im­ple­ment pre­ven­ta­tive main­te­nance strate­gies on the plant. In a BNR plant, bio-re­ac­tor pro­cesses con­sume up to 60 per­cent of the en­ergy con­sumed in the whole plant,” said En­gi­neer Ndlovu.

Be­cause the BCC was heav­ily laden by a huge wage bill, most of it be­ing over­time worked by se­cu­rity per­son­nel safe­guard­ing coun­cil in­fra­struc­ture, pal­isade fenc­ing with ra­zor wire and re­mote alarm sens­ing was put up at the plant.

“Coun­cil was un­der pres­sure to achieve the 70/30 ra­tio of ser­vice de­liv­ery to salaries and this project was im­ple­mented as one of the quick win strate­gies.

‘‘ This project is a first of its kind in wa­ter and waste wa­ter pump sta­tions and as the City of Bu­l­awayo we con­tinue in our en­deav­our to be the leader in lo­cal gov­ern­ment ex­cel­lence through in­no­va­tion.

‘‘As the first phase of in­stalling pal­isade fenc­ing and re­mote alarm sys­tems, 33 sites made up of clear wa­ter reser­voirs, sewer, wa­ter and re­claimed wa­ter pump sta­tions in the city were iden­ti­fied and equipped ac­cord­ingly. Each of these sites has sev­eral lines of de­fence against would -be in­trud­ers,” said En­gi­neer Ndlovu.

A di­lap­i­dated sewer pipe re­moved from the Marvel out­fall sewer

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