Study of Change Surface Aerator to Submerged Nonporous Aerator in Biological Pond in an Industrial Wastewater Treatment in Daura Refinery

*Omar M. Waheeb, Mohanad Mahmood Salman and Rand Qusay Kadhim*

## **Abstract**

Daura refinery, with a capacity of 140,000 barrel per stream day as a refining capacity, wastewater discharged from refining and treatment processing units, polluted water as foul water, drainages, oil spills, blowdown of boilers and cooling towers, and many other polluted water sources, aims to remove pollutants and reject clean water to the river; wastewater treatment system takes place in this treatment process. Wastewater treatment system suffers from many problems and specifically biological stage; at this stage, activated sludge with bacteria, should be supplied with oxygen, aeration system done by surface aerators with four surface fans; these fans suffer from high vibration, loss support, and in consequence, lack in oxygen supply to aerobic bacteria less than 4 ppm. The nonporous aerator is suggested as an oxygen source for the biological pool. The pilot plant builds the aim to study the ability to apply the new aeration system at the biological pool, pilot plant build with 1 cubic meter capacity tank and continuous overflow of wastewater of 10 liters.min−1, air injected with the pressure of (0.5–0.75) bar(g), and airflow of (7.6–9.7) liter.min−1 respectively. Oxygen concentration was recorded as (3.4–6.0) ppm; in terms of consumption power, changing the aeration system reduces it to less than 20%.

**Keywords:** wastewater treatment, submerged aeration, fin bubbles aeration, biological pool, activated sludge

## **1. Introduction**

Industrial wastewater treatment in refineries just receives water infected with a large number of pollutants; these pollutants are hydrocarbons (light oil products – heavy oil products), phenols [1–4], solvents, high turbidity water, saline water, foul water, drainages, and water may be discharged from equipment under maintenance or test [2]. Water with all of these pollutants is treated with a train of processes as follows:


Oxygen supply can be done by surface aeration or direct-contact air injection inside the water (porous or nonporous aeration system). Water overflows from the biological tank to another stage, which contains a secondary clarifier, overflowed water from biological reactor is treated in this clarifier (called secondary clarifier), water is separated as treated water and sludge divided into two portions, portion disposal as sludge and another portion of sludge circulated back to the bioreactor [7, 8]. The aeration tank (Biological Reactor) in an industrial wastewater treatment system needs urea and phosphoric acid, which are added to the biological reactor as a feed to bacteria, but in the municipal system, it is not required due to the high content of urea and phosphoric acid in the feed. Treated water is discharged to the river as clean treated water (**Figure 1**) [6].
