Dynamics of the self-purification processes in the waters of the Dniester river during the years 2015-2024 (Dubasari - Vadul lui Voda section)

As indices for water pollution control, the biochemical oxygen demand (BOD), chemical oxygen demand (COD) and dissolved oxygen (DO) have usually been adopted to evaluate the amount of organic components in wastewater. Recently, however, the quality of ordinary wastewater has become, due to the enormous increase in urban population and industrial growth, too complicated to examine. For this reason, the water pollution problem has been qualitatively changed.An advanced tequnique to determine organic carbon in water has recently been introduced by several researchers, who stressed the importance of Total Organic Carbon (TOC) for the classification of water pollution. Therefore, studies of the relationship among BOD, COD, and TOC appear to clarify the nature of organic constituents present in wastewater.In this paper, the author investigated the relationship among the 3 indices, BOD, COD, and TOC, which were obtained from Raw Sewage (R.S.), Secondary Effluent (S.E.) from the Kagoshima Sewage Treatment Plant (processed with activated sludge) and River Water (R.W.) in Kagoshima city.There were significant correlations between BOD and TOC, COD and TOC, and BOD and COD, respectively, in R.W. and S.E.; and also between BOD and TOC, and COD and TOC in R.S. The correlation between COD and TOC was stronger than that between BOD and TOC or that of BOD and COD in R.S. and R.W.The ratios, BOD to COD, BOD to TOC, and COD to TOC, were calculated from each sample. The ratio, BOD to COD, was more than 0.6 in both R.S. and R.W. and was 0.33 in S.E. The ratio, BOD to TOC was 2.13 in R.S. and 0.93 in S.E. These results show that both R.S. and R.W. contain a large amount of organic substances which are readily oxidized biologically. In the type of river water studied, enhanced oxygen consumption following an increase of organic substances will finally lead to irreversible water pollution. The ratio, COD to TOC, was almost equal in R.S. and S.E. Judging from the extremely small amount of TOC in S.E., it is suggested that there is successful processing of R.S. with activated sludge in the treatment plant.

- In this study, untreated sewage from five suburban sites in Sironj Tehsil, district- Vidisha, India, was evaluated for seasonal and spatial variations in Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) in 2024. The APHA 5210 B and 5220 D procedures for BOD and COD, respectively, were used to analyse 100 sewage samples from Kahra Bazar, Kathali, Bhawani Nagar, Katra Mohalla, and Hajipur. Due to runoff-driven organic matter, the BOD ranged from 159.16 to 186.96 mg/L, with Bhawani Nagar recording the highest value (186.96 mg/L) during the monsoon season (mean 180.98 mg/L). Bhawani Nagar had the highest COD (571.32 mg/L), which ranged from 337.15 to 571.32 mg/L and peaked during the monsoon (mean 511.21 mg/L). The seasons with the lowest BOD (mean 161.35 mg/L) and COD (mean 358.09 mg/L) were winter. Statistical analysis showed site-specific influences on COD (F(4,80)=8.63, p<0.001) and significant seasonal effects on both BOD (F(3,80)=36.90, p<0.001) and COD (F(3,80)=114.14, p<0.001). According to these results, there are moderate to high levels of organic pollution, which means that to prevent oxygen depletion during monsoon peaks, biological treatment with increased aeration is required. These findings support the need for customised wastewater management plans in Sironj and are consistent with those of similar Indian cities. Key Words: Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Sewage analysis, Seasonal variation, Sironj Tehsil, Organic pollution, Wastewater treatment

Many factors can affect the quality of river water in DIY, both the activities of the population and industry. Several river water quality parameters that can be used to determine the health condition of river water are Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD). This study tested the effect of TSS and DO on BOD and COD in 10 rivers in DIY. The method used is multiple linear regression modeling. Based on hypothesis testing in multiple linear regression with a significance level of 5%, it is found that TSS and DO significantly affect BOD and COD conditions in 2019. Furthermore, in 2020 only DO significantly affects COD. The prediction result is that if TSS is high then BOD and COD will be predicted to have high value. If DO is high then COD and BOD will be predicted to be low.

Rice growing in paddy fields equipped with irrigation and drainage systems is less affected by unfavorable weather patterns such as prolonged dry periods and severe storms, but for the same reason, the fields discharge water to maintain suitable water depths even between rainfall events. Studies have been done to examine the quality of water drained from rice paddy fields during or after rainfall events. However, it is not clear how drainage affects the water quality of downstream waterbodies, especially during non-rainfall periods. We investigated the water quality characteristics of rainfall and non-rainfall rice paddy drainage, which was characterized by biological oxygen demand (BOD) and chemical oxygen demand (COD). In this study, hydrological variables including water inflow/outflow rates, depth, BOD, and COD were monitored at a paddy field in Korea from 2008 to 2012. This study then quantified how BOD and COD loadings are controlled by irrigation and drainage management practices. Water quality measurements showed that rainfall events that resulted in rainfall depths greater than 50 mm are responsible for half of the overall BOD and COD loads discharged by rainfall events of the fields. On the other hand, a quarter of the total BOD and COD was attributed to events that provided rainfall depths less than 10 mm. The results suggested that the BOD and COD loads of rainfall events can be reduced by up to 25% if water at paddy fields is carefully managed in small rainfall events. Water samples taken during rainfall events had greater nutrient loads only by 6 kg BOD ha−1 (17 kg BOD ha−1 vs. 11 kg BOD ha−1) and 7 kg COD ha−1 (41 kg COD ha−1 vs. 34 kg COD ha−1) compared to those of the non-rainfall periods in the cropping season. Such a finding indicates the significant impacts of paddy field drainage practices on downstream water quality between rainfall events, particularly when considering a long period of non-rainfall. The monitoring data also showed that the standard unit load of 15.5 kg BOD ha−1 established for rice paddy fields by the Ministry of Environment, the environmental authority of Korea, is substantially different from the actual BOD load, because the non-rainfall BOD loads were not considered in the standard. Thus, this study suggests that non-rainfall BOD loads should be counted and managed for successful implementations of total maximum daily load programs.

Mining activities and community activities around the Way Umpu River have the potential to be the main source of the decline in the water quality of the Way Umpu River. Therefore, to determine the level of pollution in the Way Umpu River, it is necessary to test the quality of river water using several chemical and physical parameters such as TSS (Total Suspended Solid), DO (Dissolved Oxygen), BOD (Biological Oxygen Demand), COD (Chemical Oxygen Demand), and Phosphate. The study aims to study the differences in levels of TSS, DO, BOD, COD, and phosphate in river water before and after the mining location. The research is an observational study. Samples were taken from two points, namely the upstream (before the mining location) and the downstream (after the mining location). The average result after the analysis test is then compared with the river water quality standard in accordance with the provisions of Government Regulation no. 11 of 2012 concerning class III river water quality standards. There is no significant difference before and after mining location for the average levels of TSS, DO, BOD, and Phosphate parameters (p-value > 0.05). In the COD parameter, there is a significant difference (p-value < 0.05). Overall, the average yields of TSS, DO, BOD, COD, and Phosphate after the mining location have met the quality standards set out in accordance with Government Regulation. Therefore, it can be concluded that mining activities and community activities around the Way Umpu River have not completely decreased the water quality of the Way Umpu River in the last four years.

A demanda bioquímica de oxigênio (DBO) é uma análise de grande importância para monitoramento e dimensionamento de sistemas de tratamento biológico, além de ser referencial para legislação e verificação de impactos ambientais. A medida padrão de quantificação da concentração de material orgânico é feita com leitura após 5 dias de incubação à 20 ºC (〖"DBO" 〗_5^20) da amostra de água, propiciando comparações entre os diversos autores e em diferentes condições climáticas. Porém, em razão do longo tempo demandado para análise, há prejuízo nas tomadas de decisão em estações de tratamento de águas residuárias. Além disso, a falta de flexibilidade, no que se refere ao dia de determinação dos valores de DBO, traz transtornos do ponto de vista operacional. Poucos são os estudos que tentaram relacionar os valores de DBO obtidos em tempos diferentes com os lidos após cinco dias. Na literatura existem apenas informações entre os valores de〖"DBO" 〗_5 e a demanda bioquímica de oxigênio última (〖"DBO" 〗_u), e entre a 〖"DBO" 〗_5 e a demanda química de oxigênio (DQO). Assim, neste estudo, teve-se como objetivo a obtenção dos valores de DBO em diferentes tempos de incubação da amostra, os quais foram comparados com os valores de 〖"DBO" 〗_5, verificando-se a possibilidade de relacioná-los por meio de fatores de correção em amostras de esgoto sanitário e águas residuárias da suinocultura e de laticínios. Os resultados indicaram os fatores de correção variam com o tipo de água residuária, com a concentração de matéria orgânica que ela apresenta e com a relação entre as demandas bioquímica e química de oxigênio (biodegrabilidade do material orgânico), tendo que se ser determinado caso a caso, para cada situação, o que é pouco exequível.

The study was conducted to findout the physico-chemical and bacteriological characteristics of Noyyal River and ground water quality of Perur, India. The river water and ground water (bore well and open well) samples were collected in and around Perur and analyzed for various physico-chemical and bacteriological parameters. The study indicated that the mean value of studied parameters, except phosphate, biological oxygen demand (BOD), chemical oxygen demand (COD) of the river water and ground water samples were within the permissible limit. The parameters include total suspended solids (TSS- 132.2 mgl-1), BOD (9.55 mgl-1), COD (19.28 mgl-1), phosphate (PO4 2-- 1.58 mgl-1) and total nitrogen (TN- 2.04 mgl-1) of the river water sample were found higher when compared to the ground water samples. The bacteriological study showed that the total heterotrphic bacteria (THB - 124.4 x 103 CFU/ml), Total Coliforms (TC-2600 MPN/10ml), Faecal Coliforms (FC-1750 MPN/10ml), Faecal Streptococci (FS- 120 MPN/10ml) and FC/FS ratio (14.6) in the river water samples were found to be greater than the standard WHO limits. The generic distribution in the samples revealed that the presence of Escherichia coli, Staphylococcus, Enterobacter, Streptococci, Bacillus and Micrococcus were predominant in river water samples. The river water was found to be unfit for human consumption due to the exceeding level of Coliforms. The quality of ground water around Noyyal River was found to be safe and utilizable for cultivation purposes. If the quality management is properly maintained, the river water could be utilized for a wide range of application viz, irrigation, drinking etc.

The objective of this research was to ascertain the best conditions for efficient applications of water lettuce, giant salvinia and water hyacinth in improving the quality of low strength domestic wastewater. Water quality assessment of the wastewater samples before (influent) and after treatment (effluent) with effect to retention times (6, 12 and 24 h) was analysed. The outcome of the study at 6 h retention showed that water lettuce (6.8–7.0 pH, 50.5% colour, 46.7% biochemical oxygen demand (BOD) and 37.8% chemical oxygen demand (COD)), giant salvinia (6.9–7.1 pH, 40.5% colour, 60% BOD and 43.2% COD) and water hyacinth (6.7–6.9 pH, 45.5% colour, 53% BOD and 35.1% COD) reduction values were achieved. At 12 h retention, water lettuce (6.6–7.0 pH, 57.2% colour, 77.1% BOD and 74.6% COD), giant salvinia (6.4–6.8 pH, 81.1% colour, 66.7% BOD and 72.2% COD) and water hyacinth (6.4–6.7 pH, 61.9% colour, 70% BOD and 61.1% COD) reduction values were achieved. Similarly, for 24 h retention, water lettuce (6.6–7.0 pH, 76.7% colour, 53.2% BOD and 70.3% COD), giant salvinia (6.6–7.0 pH, 91.4% colour, 74.7% BOD and 81.0% COD) and water hyacinth (6.4–6.9 pH, 74% colour, 58% BOD and 67.2% COD) reduction values were achieved. These findings indicated that the retention times of 12 and 24 h provided suitable conditions to break down the organic contaminants present in the shallow ponds.

Thiosulfate accounted for a significant portion of the chemical oxygen demand (COD) (7 to 20 percent) and the biochemical oxygen demand (BOD) (14 to 41 percent) of the four oil shale process waters studied. Accurate measurement of the thiosulfate oxygen demand of retort water is critical in assessing its environmental impacts on receiving waters and in designing biological treatment systems to treat it. The contribution of thiosulfate to the COD of oil shale retort waters can be accurately measured in a standard COD test. The BOD of thiosulfate in retort water is more difficult to determine and may require the development of a special thiosulfate-acclimated seed. Thiosulfate recovery of a known thiosulfate spike ranged from 92 to 100 percent in the COD test and from 54 to 119 percent in the BOD test. Considerable variability in recovery was found between the process waters studied. When determining the BOD of oil shale process waters, care must be taken to insure that there is a viable population of thiosulfate-oxidizing bacteria.

The annual increase in waste at the Bantargebang Integrated Waste Management Site (IWMS) is proportionally related to leachate produced. The Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) in the Ciasem River in 2018 exceeded the water quality standards, showing the incapacity to accommodate further pollution. Therefore, this research aimed to assess capacity of the Ciasem River as the receiving water body for Integrated Wastewater Treatment Plant (IWTP) using capacity analysis based on mass balance. The results showed that the temporal water quality has been polluted since 2019 and was projected to continue until 2023, particularly regarding BOD, COD, Total Suspended Solid (TSS), and Total Nitrogen (N-Total). Spatially, high concentrations of BOD, COD, and TSS were observed upstream of the Ciasem River and increased in outfall of IWTP. At the confluence of the Cikeuting River with the Ciasem River, the concentrations of BOD, COD, and TSS showed significant changes due. Although the high concentrations of BOD and COD suggested organic matter decomposition through biological and chemical processes, there was significant no reduction in acidic pH, resulting in low toxicity for Mercury and Cadmium. These results showed that the Ciasem River has lost its capacity, particularly regarding BOD, COD, TSS, and Total Nitrogen, persisting from 2019 until 2023.

Aim: Quality of underground and Indus river surface water at Kalabagh, Pakistan was monitored to investigate the anthropogenic activities in the region because people of the Mianwali district often suffer from rusty spot on their teeth and clothes. Material and Methods: Fully flush sampling method was used for underground water samples. Surface water samples were collected from the main river flow. Conductivity, total dissolved solid (TDS), pH, chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were measured using the standard procedures. Heavy metals were determined by plasma atomic emission spectrophotometry. Results: The obtained results were compared with the set limits of National Environmental Quality Standards (NEQs) and World Health Organization (WHO). In river water samples, the average levels for BOD, COD, TDS, conductivity, pH and heavy metals were exceeding the limits of NEQs and WHO. In underground water samples of Kamer village, levels for COD, BOD, TDS and heavy metals such as cadmium and chromium were below their maximum contamination limits (MCL). However, the levels for pH, conductivity, iron and manganese were above the limits of MCL. In underground water samples from Mianwali city, the parameters including BOD, COD, TDS and heavy metals, including cadmium and chromium were below their MCL, while the conductivity, pH, and heavy metals were also observed higher than their MCL. Conclusion: The investigated parameters for river water like dissolved oxygen (DO), BOD, COD, TDS, iron, manganese, lead, cadmium were reported above MCL. In underground drinking water of Kamer village and river water samples of Mianwali city areas, the concentration levels for lead, iron and manganese were also found higher than their MCL. This may be one of cause for rusty spot on teeth and clothes of the residents. The statistical linear correlation study indicates that metals might have their origin from anthropogenic activities and natural influences.

Water quality testing was compulsory for management of safe and reliable water sources. Various sources of pollution and destruction of mangrove forest decrease the quality of river water. Thus a study was conducted to determine the water quality status of mangrove forest river water of Awat-Awat Lawas Sarawak and compare the water quality status of disturbed and undisturbed mangrove forest river in that area. Samples from twelve sampling stations were collected from both mangrove forest river from October 2013 to March 2014. In-situ data collected (pH, temperature, dissolved oxygen (DO), salinity, turbidity, total dissolved solid (TDS), conductivity) and laboratory analysis (biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammoniacal nitrogen (AN), total suspended solid (TSS)) were conducted according to the Standard method of Examination of Water and Wastewater AHPA 2005. Six water parameters: pH, DO, BOD, COD, AN and TSS value were used in calculating the Water Quality Index (WQI). Mean values for disturbed area were follows, pH (7.07), temperature (29.93°C), salinity (15.64 PSU), turbidity (55.13 NTU), DO (4.59 mg/L), BOD (0.73 mg/L), COD (10.16 mg/L), AN (0.14 mg/L), TSS (53.92 mg/L), TDS (23.14 mg/L) and conductivity (2.61 ms/m). Undisturbed area results were, pH (6.84), temperature (28.32°C), salinity (14.65 PSU), turbidity (35.41 NTU), DO (2.39 mg/L), BOD (0.55 mg/L), COD (15.82 mg/L), AN (0.13 mg/L), TSS (53.23 mg/L), TDS (22.82 mg/L) and conductivity (2.34 ms/m). There were no significant differences between two locations except for DO. Both water qualities of disturbed and undisturbed mangrove forest river were found under Class III, which describe that the water bodies are in moderate quality status.

농어촌 등에서 소규모로 발생하는 하수를 환경친화형 인공습지 하수처리장에서 효과적으로 처리하기 위하여 인공습지 하수처리장을 시공한 후 3년 동안의 수처리 효율을 조사하였다. 하수처리 시기별 오염물질 농도 변화를 조사한 결과 BOD, COD 및 부유물질은 하수원수 농도의 편차가 심하였으나, 호기성조와 혐기성조를 통과하면서 농도가 급격히 감소하여 방류수의 BOD는 0.2<TEX>${\sim}$</TEX>11.8 mg/L, COD는 1.0<TEX>${\sim}$</TEX>41.9 mg/L 및 SS 함량은 1.1<TEX>${\sim}$</TEX>6.5 mg/L이었다. 방류수의 총 질소 농도는 4<TEX>${\sim}$</TEX>60 mg/L범위로 각 조에 유입되는 총 질소 농도에 따라 편차가 심하였고, 방류수의 총 인 농도는 0.02<TEX>${\sim}$</TEX>3.51 mg/L범위이었다. 연차별 BOD, COD 및 부유물질 처리효율은 연차에 따라 큰 차이를 보이지 않았으며, 시공 후 3차년도의 방류수의 BOD, COD, 부유물질의 처리효율은 각각 97, 92 및 99%로 매우 높았다. 연차별 총 질소와 총 인의 처리효율은 호기성조 처리수와 방류수 모두에서 연차가 증가함에 따라 점차 그 처리효율이 증가하는 경향이었으며, 시공 후 3차년도의 방류수 중 총 질소 및 총 인 처리효율은 각각 62 및 73%이었다. 계절별 BOD, COD, 부유물질 및 총 인의 처리효율은 4계절 모두 큰 차이가 없었으며, 방류수의 BOD 처리효율은 97<TEX>${\sim}$</TEX>98%, COD 처리효율은 87<TEX>${\sim}$</TEX>91%, 부유물질 처리효율은 99% 및 총 인 처리효율은 76<TEX>${\sim}$</TEX>86%로 나타났다. 하지만 계절별 방류수의 총 질소 처리효율은 봄과 겨울철이 다른 계절에 비해 처리효율이 약간 감소하였고, 특히 겨울철 방류수의 총 질소 처리효율은 43%로 여름철의 61%에 비해 18%정도 감소하였다. A constructed wetland which was composed of aerobic and anaerobic areas was evaluated for 3 years to effectively treat the sewage produced in farming and fishing communities. For 3 years in a constructed wetland, biochemical oxygen demand(BOD), chemical oxygen demand(COD), suspended solids(SS), total nitrogen(T-N), and total phosphorus(T-P) in effluent were 0.2<TEX>${\sim}$</TEX>11.8, 1.0<TEX>${\sim}$</TEX>41.9, 1.1<TEX>${\sim}$</TEX>6.5, 4<TEX>${\sim}$</TEX>60 and 0.02<TEX>${\sim}$</TEX>3.51 mg/L, respectively. Removal rate of BOD, COD and SS in effluent were 97, 92 and 99%, respectively, in the third year. As time goes by, removal rate of T-N and T-P in treated water in aerobic area and effluent were gradually increased in a constructed wetland. In the third year, removal rate in effluent were 62 and 73%, respectively. By the seasons, removal rate of BOD, COD, SS, T-N and T-P were 97<TEX>${\sim}$</TEX>98, 87<TEX>${\sim}$</TEX>91, 99, 43<TEX>${\sim}$</TEX>61 and 76<TEX>${\sim}$</TEX>86%, respectively. Removal rate of BOD, COD, SS and T-P were not affected by the seasons, but that of T-N in winter and spring were decreased than the other seasons.

Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) are the major parameters used as routine surrogate tests for measuring the load of organic carbon into the environment. In this context, an evaluation of possible replacement of BOD and COD for Dissolved Organic Carbon (DOC) measurements are presented for different wastewaters. For anaerobic pond effluent, the following correlations were obtained: COD = 1.08 DOC + 79 and BOD = 0.82 DOC + 12. For facultative pond effluent, COD = -0.29DOC + 109 and BOD = 0.14DOC + 26. For raw sewage COD = 4.18DOC - 2 and BOD = 0.46COD + 5. For aerated pond effluent COD = 3.57DOC + 6 and BOD = 0.27COD + 3. For sedimentation pond effluent, COD = -1.34DOC + 138 and BOD = 0.73DOC + 16.5. Determination of COD was not appropriate for substituting classical alternatives in tested samples in despite of the limitations of the samples.

Palm Oil Mill Effluent (POME) is a highly polluting wastewater that pollutes the environment if discharged directly Owing to its high Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) concentration. This study utilizes Elaeis guineensis leaves in POME treatment to reduce the COD, BOD, and to remove colour and comply with the Department of Environment (DOE) discharge standard limit. Batch biosorption experiments were carried out for the removal of Azo dye, (AO52) using E. guineensis leaves as a potential biosorbent. The effects of various parameters, such as pH, mass of biosorbent, initial concentration, and contact time were studied to evaluate and optimize the biosorption process condition. The optimum conditions were fixed at pH 2, 90 minutes of contact time, 80ppm of initial concentration, and 1.0g amount of biosorbent. This optimum condition was then applied for COD, BOD and colour removal in POME. Under the optimum condition, maximum percentage reduction of COD, and BOD was found to be 82% and 44% respectively, and percentage of colour removal stood at 91.6%. While no standard discharge limit is stipulated for COD, the result shows that the final concentration of BOD does not comply with the standard discharge limit, specified by Environment Quality (Prescribed Premises) (Crude Palm Oil) regulations, 1977. Langmuir and Freundlich models were applied to describe the experimental data. Experimental data fitted very well with the Langmuir isotherm model. It indicates that the biosorption mechanism of E. guineensis occurs on a homogenous surface through monolayer biosorption. Further, this study reveals that E. guineensis can effectively, be used as biosorbent as the the alternative treatment of COD, BOD and color removal in POME.