Theoretical Analysis of Biogas Production from Septic Tanks: The Case of the City of Kinshasa

As many think that respect for the environment, is not only a question intended for industrialists but has all the sectors of life, in particular sanitary also. In this regard, our article brings alternative management of human waste (excrement) to solve the problems that plague our dear beautiful capital, namely: 1) Lack of latrines that meet the standards;2) Emptying of septic tanks directly into the gutters and;3) Water pollution by sewage csompanies. In order to carry out the cartographic analysis of the study area, we used Shapefile data from the OpenStreetMap, Diva-Gis. These different data allowed us, analyzed, to categorize with the software ArArcGIS 0.8.1 to produce different zones according to the cases incurred in the city of Kinshasa. To do this, the analytical method uses the Buswell equation to determine the amount of gas contained in human excrement. Focusing on the analysis of the excrements produced by the population of age superior to 10 years, for 2023, we obtained: 138355.7283 m3/day of CH4 (885476.66 kWh/day or 885.476 MWh/day), which, energy can light: 138,355 lamps of 60 to 100 W for six hours or nearly 70,000 lamps of 60 to 100 W for 12 hours. Considering the last one which offers the lowest access rate, i.e. 3% of the district population to these latrines, we have: a) In Tshangu, we produce: 1618.762 3>/day (10360.07 kWh/day or 10.36 MWh/day) which can light nearly 1600 lamps from 60 to 100 W for six hours or nearly 800 lamps from 60 to 100 W for twelve hours. b) Mont-Amba, we produce 1402.927 3>/day (8978.73 kWh/day or 8.97 MWh/day) which can light nearly 1400 lamps from 60 to 100 W for six hours or nearly 700 lamps from 60 to 100 W for twelve hours;c) In Lukunga, we produce: 946.35 3>/day (6056.66 kWh/day or 6.056 MWh/day) which can light nearly 900 lamps from 60 to 100 W for six hours or nearly 450 lamps from 60 to 100 W for twelve hours. d) Funa, we produce: 182.629 3>/day (1168.83 kWh/day or 1.17 MWh/day) which can light almost 180 lamps from 60 to 100 W for six hours or almost 90 lamps from 60 to 100 W for twelve hours.

Treatment and utilization of septic tank effluent using vertical-flow constructed wetlands and vegetable hydroponics

Vertical flow constructed wetlands is a typical ecological sanitation system for sewage treatment. The removal rates for COD, BOD 5, SS, TN, and TP were 60%, 80%, 74%, 49% and 79%, respectively, when septic tank effluent was treated by vertical flow filter. So the concentration of COD and BOD\-5 in the treated effluent could meet the quality standard for irrigation water. After that the treated effluent was used for hydroponic cultivation of water spinach and romaine lettuce, the removal efficiencies of the whole system for COD, BOD\-5, SS, TN and TP were 71 4%, 97 5%, 96 9%, 86 3%, and 87 4%, respectively. And it could meet the integrated wastewater discharge standard for secondary biological treatment plant. It was found that using treated effluent for hydroponic cultivation of vegetables could reduce the nitrate content in vegetables. The removal rates for total bacteria and coliform index by using vertical flow bed system with cinder substrate were 80%—90% and 85%—96%, respectively.

Performance of hybrid constructed wetland systems for treating septic tank effluent

The integrated wetland systems were constructed by combining horizontal-flow and vertical-flow bed, and their purification efficiencies for septic tank effluent were detected when the hydraulic retention time （HRT） was 1 d, 3 d, 5 d under different seasons. The results showed that the removal efficiencies of the organics, phosphorus were steady in the hybrid systems, but the removal efficiency of total nitrogen was not steady due to high total nitrogen concentration in the septic tank effluent. The average removal rates of COD （chemical oxygen demand） were 89%, 87%, 83%, and 86% in summer, autumn, winter and spring, respectively, and it was up to 88%, 85%, 73%, and 74% for BOD5 （5 d biochemical oxygen demand） removal rate in four seasons. The average removal rates of TP （total phosphorous） could reach up to 97%, 98%, 95%, 98% in four seasons, but the removal rate of TN （total nitrogen） was very low. The results of this study also indicated that the capability of purification was the worst in winter. Cultivating with plants could improve the treated effluent quality fTom the hybrid systems. The results of the operation of the horizontal-flow and vertical-flow cells （hybrid systems） showed that the removal efficiencies of the organics, TP and TN in horizontal-flow and vertical-flow cells were improved significantly with the extension of HRT under the same season. The removal rate of 3 d HRT was obviously higher than that of 1 d HRT, and the removal rate of 5 d HRT was better than that of 3 d HRT, but the removal efficiency was not very obvious with the increment of HRT. Therefore, 3 d HRT might be recommended in the actual operation of the hybrid systems for economic and technical reasons.

Biodegradation Potential of Some Bacteria and Fungi Isolates from Septic Tank Sewage in Some Related Sites in Delta and Edo States of Nigeria

The biodegradation potentials of some selected bacteria isolated from septic tank sewage in the region under study were examined. Three replicate samples from Locations A, B and C representing Agbor, Benin and Sapele regions of Delta and Edo States, Nigeria respectively were collected from the influent tank (raw sewage) between November 2018 and January 2019 for testing. The sewage in 10 ml septic tubes for both experimental and control samples was subjected to shake flask biodegradation analysis using the isolates with the highest screen test result. A total of 18 bio-treatment options were available in this study. In the shake flask biodegradation of sewage using isolates, total organic carbon (TOC) values from day 0 to 25 in all isolates were lower compared with the control experiments. TOC values at day 25 were lowest (0.10 mg/L) in the treatment containing Bacillus sp. + Klebsiella sp. as compared to the TOC value (2.01 mg/L) of the treatment which had Aeromonas sp. + Bacillus sp. + Klebsiella sp. pH, EC, COD, TDS, DO and BOD were also monitored for a period of 3 weeks. In all treatment options, there was a rapid increase in the BOD for the experimental set up around day 10 - 20 which ranged between 74.82 - 187.54 mg/L. The overall physical observation (odour, consistency and colour) of the experimental and the control septic tubes showed very high remarkable reductions in the experimental set-up when compared with the observation made for the control samples.

Sizing of a Wastewater Treatment System of the Center of Ngoundiane of the Alioune DiOP University of Bambey, Senegal

In our center where a lot of water is used for watering and cleaning the classrooms, the management of wastewater as a resource can be a real opportunity. The main objective of this research is to size and determine the effectiveness of natural treatments of the wastewater treatment system composed of a septic tank and a treatment plant which would be installed in site Ngoundiane of Alioune DiOP University, in Bambey, Senegal. Overall, we noted that the sized septic tank dimensioned in our study allows the efficient settling of wastewater which depends on the flow point ratio and useful settling surface area that must be lower than the upward speed that corresponds to 0.8 m/h. The sizing of the septic tank led us to obtain a useful capacity of 88 m3 and a horizontal surface of 44 m2 with a height of 2 m. The ratio between the flow of the wastewater received and the upward speed is 0.17 m/h and is significantly lower than the recommended speed. In addition, the station will be able to eliminate 80.418% of the Biochemical Oxygen Demand (BOD), 75.522% of the Chemical Oxygen Demand (COD), 92.385% of Suspended Solid (SS) and 43.427% of Nitrogen compounds.