Influence of the proportion of granular sludge and flocculent sludge on the degradation efficiency of tomato paste wastewater

The removal process of waste water sludge formed in tomato sauce processing plants was analyzed and explored. The operation mode of sequencing batch reactors (SBR) was used to explore the changes in particle sizes and the removal capacity of COD, N and P in the process of granulation; the sludge characteristics, water quality, organic pollutant degradation capacity and the optimal proportion of sludge in the mixed sludge system were analyzed when the particle sludge and flocculent sludge coexisted in different proportions. The majority of particle sizes of granular sludge are in the range of 0.45‒3 mm, and the removal rates of COD, \rmNH_4^+ —N and \rmPO_4^3- —P are over 98%, 90% and 90% respectively. When the quality ratio of granular sludge accounts for 50% of the total sludge, the removal rate of COD is the highest, which is more than 98%, the removal rate of \rmNH_4^+ —N is 78.72%, and the concentration of \rmPO_4^3- —P in the effluent is about 1.0 mg·L⁻¹, the removal rate of can reach 70.68%. The removal of nitrogen and phosphorus is also good. When the quality proportion of granular sludge is more than 75%, the removal rate of COD is higher than 98%, and the removal rate of \rmNH_4^+ —N and \rmPO_4^3- —P is higher than 90%. SVI₃₀ value is lower than 35 mL·g⁻¹, SVI₅/SVI₃₀ is close to 1, MLVSS/MLSS is 0.90, with high activity, good sludge settling performance, and vigorous growth of microorganisms. Therefore, SBR is expected to discharge aged particles, control the quality proportion of granular sludge ≥75%, and maintain the required proportion of flocculent sludge and granular sludge of 10%–25%. At the same time, the particle size range is controlled at 0.45–3.00 mm. Two way sludge discharge is used to remove particles larger than 3.0 mm together with excess flocculent sludge. The reactor has excellent organic matter removal performance. It can realize the long-term stable operation, effectively remove the granular sludge, and solve the problem of granular sludge disintegration.