Assessment of sewage sludge co-composted with coffee pulp to take advantage in Costa Rica

Abstract

In order to make use of sewage sludge in Costa Rica and to carry out the first co-composting of its kind in the country, a 150-day co-composting trial was carried out in the province of Heredia. Objective: to compare the treatment of a mixture of sewage sludge with two types of structuring agents, with and without coffee pulp, evaluating the differences in the process and the quality of the final product. Methodology: The treatments with aerobic aerated piles consisted of three control piles composting sewage sludge and shredded pruning remains as structuring material (T, % v/v 35% sewage sludge and 65% structuring material) and three piles with a co-composting treatment with coffee pulp (PL, % v/v 25% sewage sludge, structuring material with 35% coffee pulp and 40% shredded pruning remains), created with an approximate volume of 3 m3;  These were subjected to physicochemical (T, %H, pH, metals), microbiological (fecal coliforms, salmonella and helminths), maturity and stability tests. Results: Show that both treatments achieve a stable biosolid for subsequent agricultural use. The co-composting of sewage sludge mixed with coffee pulp meets quality parameters for use as amendments, being classified as class A according to U.S.EPA parameters, with no difference found in the statistical analysis when comparing the evolution of the process and the quality of the final product between treatments (T and PL).