Sludge accumulation in shallow maturation ponds treating UASB reactor effluent: results after 11 years of operation

Abstract

Polishing ponds are natural systems used for the post-treatment of upflow anaerobic sludge blanket (UASB) effluents. They are designed as maturation ponds and their main goal is the removal of pathogens and nitrogen and an additional removal of residual organic matter from the UASB reactor. This study aimed to evaluate organic matter and suspended solids removal as well as sludge accumulation in two shallow polishing ponds in series treating sanitary effluent from a UASB reactor with a population equivalent of 200 inhabitants in Brazil, operating since 2002. For this evaluation, long-term monitoring of biochemical oxygen demand and total suspended solids and bathymetric surveys have been undertaken. The ponds showed an irregular distribution of total solids mass in the sludge layer of the two ponds, with mean accumulation values of 0.020 m(3) person(-1) year(-1) and 0.004 m(3) person(-1) year(-1) in Ponds 1 and 2, leading to around 40% and 8% of the liquid volume occupied by the sediments after 11 years of operation. The first pond showed better efficiency in relation to organic matter removal, although its contribution was limited, due to algal growth. No simple input-output mass balance of solids can be applied to the ponds due to algal growth in the liquid phase and sludge digestion in the sludge.

Upgrading and evaluation of a simple pond system for small communities with simple interventions to reduce land requirements and increase performance

“…The first pond accumulated a large amount of sludge over the previous 11 years (Possmoser-Nascimento et al 2014) and was investigated regarding ammonia and nitrogen fractions removal (Rodrigues et al 2015).…”

Review of Upflow Anaerobic Sludge Blanket Reactor Technology: Effect of Different Parameters and Developments for Domestic Wastewater Treatment

“…They are mainly used as maturation ponds for the removal of pathogens, nitrogen, and remaining organic matter from the UASB reactor effluent [65]. The use of sequential anaerobicaerobic technology such as UASB-activated sludge for municipal wastewater treatment combines the benefits of both systems in an economical arrangement.…”

Stratification and equalization cycles in shallow maturation ponds with different operational configurations and at different periods of the year

“…• Phase 1 (May 2013 to December 2013): the two ponds operated in parallel, one with over 11 years of accumulated sediment on the bottom in approximately 40% of the useful volume, distributed as presented in the work of Possmoser-Nascimento et al (2014), and the other pond without sludge (recently removed), with a depth of 0.82 m each.…”

“…In the case of pond 1, tests were made with the bottom probe placed at the interface of the liquid with the sediment (just above the sediment) and with the probe completely immersed in the sediment. Thus, to determine the depths for placing the probes in pond 1 exactly at the interface, the bathymetric map of the pond's sediments (Possmoser-Nascimento et al 2014) was consulted and preliminary field tests were done, with the same device used for Passos et al (2014) and Possmoser-Nascimento et al (2014) to obtain the height of the accumulated sludge. Measurement frequency varied according to the data collection program and storage capacity of the devices, comprising intervals of 1-30 minutes.…”