SEWAGE TREATMENT, SLUDGE DRYING AND PRODUCTION OF SUPERPHOSPHATE FERTILIZER USING MAGNESIUM SULFATE, PHOSPHATE ORE AND SULFURIC ACID

Abstract

Public awareness and the demand towards better environmental quality standards, led to the establishment of more and more wastewater treatment (WWT) plants. The main goals of all currently published researches focus on how to enhance WWT process either by introducing chemicals (coagulants and flocculants), adjusting wastewater pH, temperature… etc. In addition to utilizing sewage sludge (SS) and eliminating its risk has been one of their top goals.

One of the commonly used SS management methods is its utilization in agriculture. However, a lot of researches mention the disadvantages of using SS in agriculture as it contains pathogens, and toxic materials. Moreover, more than 90% of SS is water that is why it must be first dewatered to reduce its volume.

The current thesis focuses on enhancing both WWT and sludge dewatering to be further utilized as a fertilizer (single superphosphate (SSP)) by introducing magnesium sulfate (MgSO4), phosphate ore and sulfuric acid (H2SO4) in different routes. In first route MgSO4 and phosphate ore were added to primary settling tank where MgSO4 dose and MgSO4 to phosphate ore were optimized as well as phosphate ore particle size. The optimum results were achieved when MgSO4 dose of 1500 mg/l of wastewater is used with MgSO4: Phosphate ore =1:5 and phosphate ore mean particle size 0.1125mm. In the second route MgSO4 and phosphate ore were added to SS. After that H2SO4 was added to the settled sludge to produce SSP. From the tests results three graphs relating MgSO4 doses with total, water extract and citric extract of P2O5 were constructed using 10 wt% H2SO4.