The effect of algal biomass on the removal of faecal coliform from domestic wastewater

A promising system consisting of Up-flow Anaerobic Sludge Blanket (UASB) and Down-Flow Hanging Sponge (DHS) system was investigated for removal of COD, BOD5 fractions, ammonia and faecal coliform from domestic wastewater. The combined system was operated at different HRTs of 16, 11 and 8 h. The results indicate that increasing the total HRT from 8 to 16 h significantly (p < 0.05) improves the CODtotal and BOD5 total removal mainly as a result of a higher removal of CODsoluble, BODsoluble, CODparticulate and BODparticulate. The main part of coarse suspended solids was removed in the UASB reactor (76.4±18%) and the remaining portion was adsorbed and/or enmeshed and degraded in the biomass of the DHS system. The combined system achieved a substantial reduction of total suspended solids (TSS) resulting in an average overall percentage removal of 94±6% (HRT = 16 h) and 89.5±7.8% (HRT = 8 h). Faecal coliform reduction was significantly improved when increasing the total HRT from 8 to 16 h. Residual counts of faecal coliform were 3.1 × 103/100 ml at a total HRT of 16 h, and 2.8 × 104/100 ml at total HRT of 8 h, corresponding to overall removal efficiency of 99.97±0.03 and 99.6±0.3% respectively. Despite the increase of ammonia concentration as a result of protein hydrolysis in the UASB reactor, a substantial removal of ammonia was achieved in the DHS system. The results obtained show that decreasing the OLR imposed to DHS system from 2.6 to 1.6 kg COD/m3·d significantly (p < 0.05) improves the removal efficiency of ammonia by a value of 29%. However, the removal efficiency of ammonia is not further increased when decreasing the OLR from 1.6 to 1.3 kg COD/m3·d. The discharged sludge from UASB + DHS system exerts a good settling property and partially stabilized. DHS profile results have shown that the major part of COD, BOD5, and TSS was removed in the upper part of the system, consequently, the nitrification process was occurring in the lower part of the DHS system.

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Evaluation of high rate ponds operational and design strategies for algal biomass production and domestic wastewater treatment

The Science of The Total Environment ◽

10.1016/j.scitotenv.2021.148362 ◽

2021 ◽

pp. 148362

Author(s):

Eduardo Couto ◽

Maria Lúcia Calijuri ◽

Paula Assemany ◽

Paulo Roberto Cecon

Keyword(s):

Wastewater Treatment ◽

Biomass Production ◽

Algal Biomass ◽

Domestic Wastewater ◽

High Rate ◽

Design Strategies ◽

Domestic Wastewater Treatment

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Removal of faecal coliforms in a wastewater stabilisation pond system in Mindelo, Cape Verde

Water Science & Technology ◽

10.2166/wst.1996.0274 ◽

1996 ◽

Vol 34 (11) ◽

pp. 149-157 ◽

Cited By ~ 5

Author(s):

M. Rångeby ◽

P. Johansson ◽

M. Pernrup

Keyword(s):

Waste Water ◽

Retention Time ◽

Domestic Wastewater ◽

Cape Verde ◽

Faecal Coliform ◽

Coliform Bacteria ◽

Faecal Coliforms ◽

Pond System ◽

In Series ◽

Influent Wastewater

In Mindelo, Cape Verde, domestic wastewater is treated in a waste water stabilisation pond system with the aim of reusing the water for agricultural purposes. The conductivity in influent wastewater is high and in order to minimise an increase in the conductivity the plant is operated with as low retention time as possible. An investigation was performed over two and a half months in 1995 with the aim of finding factors that affect the removal of faecal coliform bacteria. COD, conductivity, flow, pH and faecal coliforms were then followed through the system. The results show that the die-off rate, K, is high when the pH is high. The results also indicate that the retention time seems to be the most important factor, which means that the plant has to be operated with at least 3-4 maturation ponds in series and the inlets and outlets have to be constructed in a way that avoids short-circuiting. It was also found that not only the evapuation but also chemical and/or biological reactions affect the conductivity. This phenomenon will be investigated further.

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