Northern Rivers Ecosystem Initiative: Nutrients and Dissolved Oxygen – Issues and Impacts

Anthropogenic inputs of nitrogen (N), phosphorus (P) and oxygen-consuming material to aquatic ecosystems can change nutrient dynamics, deplete oxygen, and change abundance and diversity of aquatic plants and animals. The Northern Rivers Ecosystem Initiative required a research and assessment program to establish the contribution of pulp mill and sewage discharges to eutrophication and depressions in dissolved oxygen (DO) in the Athabasca and Wapiti rivers of northern Alberta, Canada and examine the adequacy of existing guidelines for protecting these systems. Analysis of long-term data showed that total N (TN) and total P (TP) concentrations in exposed river reaches exceeded concentrations in reference reaches by ≤ 2 times for the Athabasca River, and by 9.6 (TP) and 2.6 (TN) times for the Wapiti River. Results from nutrient limitation experiments conducted in situ and in mesocosms showed that benthic algal production was nutrient sufficient downstream of pulp mill discharges but constrained in upper river reaches by insufficient P (Athabasca River) or N + P (Wapiti River). Dissolved oxygen (DO) concentrations in both rivers declined during winter such that median concentrations in the Athabasca River 945 km downstream of the headwaters were approximately 8 mg L⁻¹ in mid-February. Although water column DO rarely approached the guideline of 6.5 mg L⁻¹, DO studies undertaken in the Wapiti River showed that pore water DO often failed to meet this guideline and could not be predicted from water column DO. Results from this integrated program of monitoring and experimentation have improved understanding of the interactions between nutrients, DO and aquatic ecosystem productivity and resulted in recommendations for revisions to nutrient and DO guidelines for these northern rivers.The Canadian Crown reserves the right to retain a non-exclusive, royalty free licence in and to any copyright.     

Reduction of dissolved organic matter in terms of DOC, UV-254, SUVA and THMFP in industrial estate wastewater treated by stabilization ponds

The aim of this research was to monitor the influent and effluent water quality of the aeration, facultative and oxidation water treatment ponds of an industrial estate. This industrial estate, the largest in northern Thailand, has proposed to utilization of reclaimed treated wastewater in their raw water supply so as to cope with the yearly water shortage during the dry season. Water samples were collected four times from four sampling points and evaluated for their dissolved organic matter (DOM) content in terms of dissolved organic carbon (DOC), ultraviolet light absorbance at 254 nm (UV-254), specific ultraviolet absorption (SUVA), trihalomethane formation potential (THMFP) and trihalomethane (THM) species. Average values of DOC, UV-254, SUVA and THMFP in the influent wastewater of 12.9 mg L⁻¹, 0.165 cm⁻¹, 1.29 L mg⁻¹m⁻¹ and 1.24 mg L⁻¹, respectively, were observed. The aeration ponds produced the best results: a 54% reduction of DOC, a 33% reduction of UV-254, and a 57% reduction of THMFP. However, SUVA in the aeration pond effluent showed a moderate increase. The facultative ponds and oxidation ponds did not take part in the reduction of DOC, UV-254, SUVA and THMFP. Average DOC, UV-254, SUVA and THMFP value of the treated wastewater were 5.8 mg L⁻¹, 0.107 cm⁻¹, 1.85 L mg⁻¹m⁻¹ and 468 μg L⁻¹, respectively. Chloroform, at 72.6% of total THMFP, was found to be the predominant THM species.     

Applicability of high rate transpiration system for treatment of biologically treated distillery effluent

The biologically treated distillery effluent (BTDE) contains intense colour, high total dissolved solids (TDS), chemical oxygen demand (COD) and biochemical oxygen demand (BOD). These properties even after primary, secondary and tertiary treatments contain high concentrations of TDS, COD and BOD. The paper highlights the safe disposal and treatment of BTDE on land through High Rate Transpiration System (HRTS). HRTS is a zero discharge, low cost, high-tech method for improving the quality of BTDE for potential reuse. The experiments conducted at bench and pilot scale showed that HRTS having coconut husk as a bedding material could successfully treat the BTDE with a hydraulic load of 200 m³ ha⁻¹ day⁻¹ having BOD of 100 mg l⁻¹ and 500 m³ ha⁻¹ day⁻¹ having BOD of 500 mg l⁻¹ with average COD load of 0.686 and 2.88 ton ha⁻¹ day⁻¹ during the post and pre monsoon periods respectively. There was no significant increase in the organic carbon of the soil irrigated with BTDE. The concentrations of various pollutants analyzed in the leachate were within the prescribed limit for the drinking water sources. The colour removal was 99 to 100% and BOD and COD were possible to treat with optimum hydraulic loading of BTDE through HRTS planted with Dendrocalamus strictus.     

Environmental assessment of water-courses of the Turvo Limpo River basin at the Minas Gerais State, Brazil

A study was performed to evaluate the environmental contamination in the Turvo Limpo River basin which receives effluent discharges from domestic (residential and commercial) activities. The watercourses examined were the São Bartolomeu Stream, Turvo Sujo River, and Turvo Limpo River, located in the Minas Gerais State, Brazil. Water samples were collected at the river-side and analyzed for evaluation of pollutant inputs. The pH, temperature, electrical conductivity, redox potential (Eh), dissolved oxygen (DO), total and settleable solids, visual color, hardness, chemical oxygen demand (COD), biochemical oxygen demand (BOD), chloride, total phosphate, total nitrogen, ammonia nitrogen, nitrate, total coliforms and E. coli, as well as the Cd, Pb, Cu, and Zn speciation were determined in the watercourses. The data obtained were compared with those of the Brazilian Environmental Standards and with data from non-contaminated areas. River water characteristics in some sites were far from the limit values established for superficial waters with satisfactory quality. For instance, the BOD values reached 411 mg L^?1 for a maximum limit of 10.0 mg L^?1, while the ammonia nitrogen concentration reached 28 mg L^?1 for a maximum limit of 13.3 mg L^?1. Some sites showed E. coli values above those of non-contaminated regions. Besides the effects of sewage discharges into the water-courses, agriculture activities and the use of the area for cattle husbandry influenced the quality of the river waters, for instance, the pH of a spring-water sample reached the value of 4.3. The São Bartolomeu Stream has been contributing to the deterioration of the water quality of the Turvo Sujo River, while the Turvo Limpo River has also been affected by anthropogenic discharges in the Turvo Sujo River. The speciation of Cd, Cu and Pb showed that these metals were mainly found in the particulate fraction (i. e., associated with the suspended material). Fifty five percent of the water samples showed labile Zn concentrations greater than that of the nonlabile Zn.     

Application of a Larval Medaka Assay to Evaluate the Fish Safety Level in Sagami River, Japan

Physico-chemical characteristics of some river and hand-dug well waters used for drinking and domestic purposes in the oil rich Niger Delta area of Nigeria were assessed using standard methods. The concentrations of the parameters in the river water samples ranged in the following order: pH (5.6–6.9), temperature (26.90–28.60°C), turbidity (23–63 NTU), electrical conductivity (52–184 μs/cm), DO (5.4–7.2 mg/l), BOD (21–57 mg/l), TDS (6.0–217 mg/l), PO₄ ³⁻ (0.19–1.72 mg/l), SO₄ ²⁻ (25–36.8 mg/l), NO₃ ⁻ (20.3–28 mg/l), Fe (6.07–15.71 mg/l), Zn (0.04–0.24 mg/l), Pb (0.01–0.17 mg/l), Ni (0.01–0.13 mg/l), Vn (0.01–0.20 mg/l) and Hg (0.001–0.002 mg/l). The concentrations of these parameters in the hand-dug well water ranged in the following order: pH (5.7–6.8) temperature (26–30°C), turbidity (134–171 NTU), electrical conductivity (160–340 μs/cm), DO (5.4–6.4 mg/l), BOD (13–34 mg/l), TDS (110–190 mg/l), PO₄ ³⁻ (0.84–1.84 mg/l), SO₄ ²⁻ (10.6–28.1 mg/l), NO₃ ⁻ (11.3–23 mg/l), Fe (13.17–16.31 mg/l), Ni (0.01–0.02 mg/l), Vn (0.01–0.04 mg/l) and Hg (0.001–0.004 mg/l). The concentrations of BOD, turbidity, NO₃ ⁻ and Fe in the water samples were above WHO and FMENV permissible limits for safe drinking water. The results suggest that the use of such waters for drinking and domestic purposes pose a serious threat to the health of the users and calls for the intervention of government agencies.     

Development of Dissolved Oxygen Model for a Highly Variable Flow River: A Case Study of Ravi River in Pakistan

A framework for dissolved oxygen (DO) modeling of the Ravi River has been developed based on a combination of laboratory measurements and field and monitoring data. Both the classical Streeter-Phelps (CSP) and the modified Streeter-Phelps (MSP) models are used for DO simulations. The MSP model considers the carbonaceous biochemical oxygen demand (CBOD) and nitrogenous biochemical oxygen demand (NBOD) separately, whereas the CSP model is evaluated considering only the CBOD and NBOD is incorporated in the overall BOD utilization rate. CBOD, NBOD and BOD rates have been determined through long-term BOD analysis of five main wastewater outfalls and two surface drains discharging into the Ravi River over a 98 km stretch. Analysis by Thomas Method manifests strong coefficient of determination “R²” between 0.72 and 0.98 for all the three types of BOD rates. Sensitivity analyses have also been carried out to find out a suitable reaeration rate formula for highly variable flows in the Ravi River. The CSP model results based on classical approach of considering only CBOD show significant difference between the model predictions and field measurements suggesting that NBOD needs to be incorporated for the model development. The dissolved oxygen values calculated using the MSP model and the CSP model based on overall BOD rate are in close agreement with field measurements and are thus suitable to model DO levels in the Ravi River.     

Determination of heavy metal pollution with environmental physicochemical parameters in waste water of Kocabas Stream (Biga, Canakkale, Turkey) by ICP-AES

Waste water pollution of industrial areas can answer for the serious consequences of one of the most important environmental threats to the future. In this study, inductively coupled plasma-atomic emission spectrometry method (ICP-AES) is proposed to determine heavy metals (Pb, Cu, Cd, Cr, Zn, Al, Fe, Ni, Co, Mn) and major elements (Ca, Mg) in waste water of Kocabas Stream. The concentration of metals in the waste water samples taken from 9 different stations (St.) in Biga-Kocabas Stream in November 2004 (autumn period) were determined after simple pretreatment of samples by the proposed ICP-AES method. An analysis of a given sample is completed in about 15 min for ICP-AES the method. The results of heavy metals concentrations in waste water were found between 0.00001–77.69610 mg l⁻¹ by the ICP-AES technique. The concentrations of Pb, Cd, Cu, Zn, Cr, Al, Fe, Mn, Ni, Co, Mg and Ca 0.00001 (St.3,6,7) – 0.0087 mg l⁻¹ (St.9), 0.00001 (St.4-7) – 0.0020 mg l⁻¹ (St.8), 0.00001 (St.1,3-7,9) – 0.0041 mg l⁻¹ (St.2), 0.0620 (St.2) – 0.2080 mg l⁻¹ (St.3), 0.0082 (St.6) – 0.2290 mg l⁻¹ (St.8), 0.3580 (St.2) – 1.7400 mg l⁻¹ (St.3), 0.2240 (St.1) – 0.6790 mg l⁻¹ (St.3), 0.0080 (St.1) – 1.5840 mg l⁻¹ (St.3), 0.0170 (St.3) – 0.0640 mg l⁻¹ (St.2), 0.0010 (St.1,4,5,8) – 0.0080 mg l⁻¹ (St.3), 5.0640 (St.9) – 5.2140 mg l⁻¹ (St.1) and 43.3600 (St.2) – 77.6961 mg l⁻¹ (St.9), respectively. Also we measured environmental physicochemical parameters such as temperature, salinity, specific conductivity, total dissolved solid (TDS), pH, oxidation and reduction potential (ORP), and dissolved oxygen (DO) in the waste water at sampling stations.     

地表水BOD_5的快速预测预报

地表水五日生化需氧量（ＢＯＤ５）的测试需要五天时间，分析周期较长。本文建立了ＢＯＤ５与高锰酸盐指数（ＣＯＤＭｎ）、ＢＯＤ５与溶解氧（ＤＯ）之间的直线回归方程，通过测定地表水的ＣＯＤＭｎ和ＤＯ可分别对地表水的ＢＯＤ５实现快速预测预报。现场使用溶解氧测定仪检测ＤＯ，可立即预报地表水的ＢＯＤ５。     

Sensitivity Analysis and Water Quality Modeling of a Tidal River Using a Modified Streeter–Phelps Equation with HEC-RAS-Calculated Hydraulic Characteristics

A modified Streeter–Phelps equation and the Hydrological Engineering Centers River Analysis System (HEC-RAS) were combined to assess water quality of the Tan-Sui River and its tributaries. The Tan-Sui River is the main source of water supply for northern Taiwan, and the water quality of its stream is significantly affected by tides. In this study, HEC-RAS was employed to assess the impact of tides on water quality and to calculate reoxygenation coefficients. The modified Streeter–Phelps equation was used to calculate water quality in terms of contaminant degradation and reoxygenation. Biochemical oxygen demand (BOD) and ammonia nitrogen (NH₃–N), the most important identified sources of water pollution in the rivers investigated, were evaluated. Dissolved oxygen (DO) was also simulated, since it is often used as a staple of water quality. Results showed that employing HEC-RAS for hydraulic calculations improves the modified Streeter–Phelps simulation. In river sections without tidal influence, water quality was sensitive to the BOD and NH₃–N degradation constants. Downstream of Chin-Mei Creek, while the BOD degradation constant decreased by 80%, BOD and DO concentrations increased from 7.1?mg/L to 10.7?mg/L and 5.0?mg/L to 7.2?mg/L, respectively, indicating that water quality was not as sensitive to variations of the BOD degradation constant as expected. The concentrations of DO and BOD at the river mouth had a significant impact on water quality for the tidal sections of the investigated rivers due to mixing of tidal and river waters. The BOD and NH₃–N degradation constants in the tidal sections had little impact on water quality simulations. This study demonstrated the innovative combination of the modified Streeter–Phelps equation and HEC-RAS to assess the impact of tidal variation and to simulate the water quality of a tidal river when available data is rather limited.     

Ecological study of river Suswa: modeling DO and BOD

In this paper limnological status of river Suswa was observed for a period of two years. A water quality Beck modified Khanna Bhutiani model (BMKB model) was developed to calculate DO (dissolved Oxygen) and BOD (biochemical oxygen demand). The model was developed to calculate DO and BOD by using DO/BOD of same place and upstream in previous season which results in Single output. This model gives the seasonal value on the basis of previously taken upstream and downstream observations/concentrations of DO and BOD. The model was calibrated and verified for the water quality data (Physico-chemical data) of samples collected from river Suswa in different seasons. The model gave good agreement between data observed by it and the data observed manually, thus substantiating the validity of the model. Only minor differences were observed in physical, chemical and heavy metals of all the four sampling stations during the course of study.     

Assessment of temporal and spatial water quality in international Gomishan Lagoon,Iran, using multivariate analysis

Coastal lagoon ecosystems are vulnerable to eutrophication, which leads to the accumulation of nutrients from the surrounding watershed over the long term. However, there is a lack of information about methods that could accurate quantify this problem in rapidly developed countries. Therefore, various statistical methods such as cluster analysis (CA), principal component analysis (PCA), partial least square (PLS), principal component regression (PCR), and ordinary least squares regression (OLS) were used in this study to estimate total organic matter content in sediments (TOM) using other parameters such as temperature, dissolved oxygen (DO), pH, electrical conductivity (EC), nitrite (NO₂), nitrate (NO₃), biological oxygen demand (BOD), phosphate (PO₄), total phosphorus (TP), salinity, and water depth along a 3-km transect in the Gomishan Lagoon (Iran). Results indicated that nutrient concentration and the dissolved oxygen gradient were the most significant parameters in the lagoon water quality heterogeneity. Additionally, anoxia at the bottom of the lagoon in sediments and re-suspension of the sediments were the main factors affecting internal nutrient loading. To validate the models, R², RMSECV, and RPDCV were used. The PLS model was stronger than the other models. Also, classification analysis of the Gomishan Lagoon identified two hydrological zones: (i) a North Zone characterized by higher water exchange, higher dissolved oxygen and lower salinity and nutrients, and (ii) a Central and South Zone with high residence time, higher nutrient concentrations, lower dissolved oxygen, and higher salinity. A recommendation for the management of coastal lagoons, specifically the Gomishan Lagoon, to decrease or eliminate nutrient loadings is discussed and should be transferred to policy makers, the scientific community, and local inhabitants.     

Spatiotemporal trend analysis of recent river water quality conditions in Japan

In order to promote pollutant monitoring and preservation of water resources, we evaluate the spatiotemporal trends in recent water quality conditions in Japanese rivers. Trend analysis is conducted on the 92 major rivers in Japan using the available water quality data recorded from 1992 to 2005 and the characteristics of major pollutants in these rivers are analyzed. Spatial and temporal analysis of trends for six water quality indicators is conducted using the Mann Kendall test, a non-parametric statistical method. The indicators analyzed are biochemical oxygen demand (BOD), chemical oxygen demand (COD), dissolved oxygen (DO), total nitrogen (TN), total phosphorus (TP) and pH. The majority of sampling locations monitoring BOD, COD, TN and TP show trends toward decreasing concentrations over time. Many sampling locations show increasing DO concentrations. Our results show that water quality in Japanese rivers has improved dramatically over the past decade, although there are still problems in some places, most notably in the Hokkaido, Kanto, Kinki and Kyushu regions. The improvements seen in water quality appear to be the result of improved wastewater treatment and other water quality improvement efforts achieved through government initiative.     

Status and Trends of Dissolved Oxygen in Corpus Christi Bay, Texas, U.S.A.

The purpose of this studywas to determine status and long-term trends of dissolved oxygen concentrations (DO) in Corpus Christi Bay, Texas, U.S.A. A 20-year record of randomized stations was used to determine the trend of surface water DO, salinity, and temperature over space and time. A 13-year record of two fixed stations was used to determine the temporal nutrient trends. A 10-year record of fixed stations in the southeastern region of Corpus Christi Bay was used to determine the status of disturbance caused by low DO in bottom waters. From 1982 to 2002, there was a significant decrease in surface water DO at a rate of 0.06 mg L⁻¹ yr⁻¹ and a significant increase in surface water temperature at a rate of 0.07°C yr⁻¹. The southeastern region of Corpus Christi Bay had the lowest average DO, and during July and August, DO are steadily declining at a rate of 0.09 mg L⁻¹ yr⁻¹. It is not likely that eutrophication is causing hypoxia, because freshwater inflow rates have significantly decreased since 1941 and nutrient levels have not changed from 1987 to 2000. Even though long-term trends indicate that average surface DO is decreasing, disturbance by hypoxia appears to be stable, but this may be due to just eight years of data. In fact, if the current trend continues, surface water DO will not meet exceptional aquatic life standards (≤5 mgL⁻¹) in 2032.     

Water Quality Changes in Chini Lake, Pahang, West Malaysia

A study of the water quality changes of Chini Lake was conducted for 12 months, which began in May 2004 and ended in April 2005. Fifteen sampling stations were selected representing the open water body in the lake. A total of 14 water quality parameters were measured and Malaysian Department of Environment Water Quality Index (DOE-WQI) was calculated and classified according to the Interim National Water Quality Standard, Malaysia (INWQS). The physical and chemical variables were temperature, dissolved oxygen (DO), conductivity, pH, total dissolved solid (TDS), turbidity, chlorophyll-a, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solid (TSS), ammonia-N, nitrate, phosphate and sulphate. Results show that base on Malaysian WQI, the water in Chini Lake is classified as class II, which is suitable for recreational activities and allows body contact. With respect to the Interim National Water Quality Standard (INWQS), temperature was within the normal range, conductivity, TSS, nitrate, sulphate and TDS are categorized under class I. Parameters for DO, pH, turbidity, BOD, COD and ammonia-N are categorized under class II. Comparison with eutrophic status indicates that chlorophyll-a concentration in the lake was in mesotrophic condition. In general water quality in Chini Lake varied temporally and spatially, and the most affected water quality parameters were TSS, turbidity, chlorophyll-a, sulphate, DO, ammonia-N, pH and conductivity.     

Assessment of seasonal effects of municipal sewage pollution on the water quality of an urban canal—a case study of the Buckingham canal at Kalpakkam (India): NO3, PO4, SO4, BOD, COD and DO

The seasonal effects of untreated and treated municipal sewage on the nutrients-nitrate (NO(3)), phosphate (PO(4)), sulphate (SO(4)), and the biochemical oxygen demand (BOD), chemical oxygen demand (COD) and dissolved oxygen (DO) of the receiving urban canal, the Buckingham canal at Kalpakkam (Tamil Nadu, India) was monitored monthly during pre- monsoon-2005 to post-monsoon-2006. The NO(3), PO(4) and SO(4) contents were higher in the downstream than that of the upstream of the outfall points of treated as well as untreated sewage, of the canal. The NO(3) and PO(4) contents were higher during summer than that of monsoon; however the SO(4) was higher during winter and lower during summer in the canal water. The BOD and COD were lower and DO was higher at the upstream than that of downstream of the canal. The concentrations of BOD and COD were higher during summer season, which decreased during monsoon season, while the DO decreased during the summer season and increased in monsoon season in the canal water. Cluster analysis applied to the six sampling points of the canal, has grouped them based on the water quality similarities.     

Water quality and dissolved inorganic fluxes of N,P, SO<Subscript>4</Subscript>, and K of a small catchment river in the Southwestern Coast of India

The southwestern coast of India is drained by many small rivers with lengths less than 250 km and catchment areas less than 6,500 km². These rivers are perennial and are also the major drinking water sources in the region. But, the fast pace of urbanization, industrialization, fertilizer intensive agricultural activities and rise in pilgrim tourism in the past four to five decades have imposed marked changes in water quality and solute fluxes of many of these rivers. The problems have aggravated further due to leaching of ionic constituents from the organic-rich (peaty) impervious sub-surface layers that are exposed due to channel incision resulting from indiscriminate instream mining for construction-grade sand and gravel. In this context, an attempt has been made here to evaluate the water quality and the net nutrient flux of one of the important rivers in the southwestern coast of India, the Manimala river which has a length of about 90 km and catchment area of 847 km². The river exhibits seasonal variation in most of the water quality parameters (pH, electrical conductivity, dissolved oxygen, total dissolved solids, Ca, Mg, Na, K, Fe, HCO₃, NO₂-N, NO₃-N, P _\text-inorg_{\rm \text{-}inorg}, P _\text-tot_{\rm \text{-}tot}, chloride, SO₄, and SiO₂). Except for NO₃-N and SiO₂, all the other parameters are generally enriched in non-monsoon (December–May) samples than that of monsoon (June–November). The flux estimation reveals that the Manimala river transports an amount of 2,308 t y^− 1 of dissolved inorganic nitrogen, 87 t y^− 1 dissolved inorganic phosphorus, and 9246 t y^− 1 of SO₄, and 1984 t y^− 1 K into the receiving coastal waters. These together constitute about 23% of the total dissolved fluxes transported by the Manimala river. Based on the study, a set of mitigation measures are also suggested to improve the overall water quality of small catchment rivers of the densely populated tropics in general and the south western coast in particular.     

Water Quality Assessment of an Untreated Effluent Impacted Urban Stream: The Bharalu Tributary of the Brahmaputra River, India

Guwahati, the lone city on the bank of the entire midstream of the Brahmaputra River, is facing acute civic problem due to severe depletion of water quality of its natural water bodies. This work is an attempt towards water quality assessment of a relatively small tributary of the Brahmaputra called the Bharalu River flowing through the city that has been transformed today into a city drainage channel. By analyzing the key physical, chemical and biological parameters for samples drawn from different locations, an assessment of the dissolved load and pollution levels at different segments in the river was made. Locations where the contaminants exceeded the permissible limits during different seasons were identified by examining spatial and temporal variations. A GIS developed for the watershed with four layers of data was used for evaluating the influence of catchment land use characteristics. BOD, DO and total phosphorus were found to be the sensitive parameters that adversely affected the water quality of Bharalu. Relationship among different parameters revealed that the causes and sources of water quality degradation in the study area were due to catchments input, anthropogenic activities and poor waste management. Elevated levels of total phosphorus, BOD and depleted DO level in the downstream were used to develop an ANN model by taking total phosphorus and BOD as inputs and dissolved oxygen as output, which indicated that an ANN based predictive tool can be utilized for monitoring water quality in the future.     

Eco-hydrodynamic Modelling of Chini Lake: Model Description

In this study, we coupled a three-dimensional hydrodynamic model with an ecosystem model and applied it to the shallow complex floodplain wetland of Chini Lake in Malaysia. Our objective was to provide a better understanding of the lake’s ecosystem dynamics under different forcing mechanisms. Simulations and validation were performed over a dry month period. Wind speed ranged between 0 and 7.7 m s^?1, whilst air temperature ranged between 22.0 and 35.6 °C. Advective transport driven by wind stress was the dominant physical force that shaped the water quality variations during the dry season. Convective circulation intermittently influenced the circulation during calm conditions. Nutrient concentration and stratification of dissolved oxygen (DO) varied between the lakes. Wind events saw patterns of the surface DO concentrations move spatially in the direction of the wind. The ecosystem model simulation suggested that the water quality in Chini Lake was influenced by macrophyte production, although the dissolved and particulate organic carbon accounted for the major fraction of organic matter content in the lake.     

Inorganic nitrogen transformations in the treatment of landfill leachate with a high ammonium load: A case study

The inorganic nitrogen transformations occurring at a municipal waste leachate treatment facility were investigated. The treatment facility consisted of a collection well and an artificial wetland between two aeration ponds. The first aeration pond showed a decrease in ammonium (from 3480 (± 120) to 630(± 90) mg ⋅ L⁻¹), a reduction in inorganic nitrogen load (3480 to 1680 mg N ⋅ L⁻¹), and an accumulation of nitrite (< 1.3 mg-N ⋅ L⁻¹ in the collection well, to 1030 mg-N ⋅ L⁻¹). Incomplete ammonium oxidation was presumably the result of the low concentration of carbonate alkalinity (∼2 mg ⋅ L⁻¹), which may cause a limitation in the ammonium oxidation rate of nitrifiers. Low carbonate alkalinity levels may have been the result of stripping of CO₂ from the first aeration pond at the high aeration rates and low pH. Various chemodenitrification mechanisms are discussed as the reason for the reduction in the inorganic nitrogen load, including; the reduction of nitrite by iron (II) (producing various forms of gaseous nitrogen); and reactions involving nitrous acid. It is suggested that the accumulation of nitrite may be the result of inhibition of nitrite oxidizers by nitrous acid and low temperatures. Relative to the first aeration pond, the speciation and concentration of inorganic nitrogen was stable in the wetlands and 2nd aeration pond. The limited denitrification in the wetlands most probably occurred due to low concentrations of organic carbon, and short retention times.     

Evaluation of pollution load of Lahore Canal by quantification of various pollutants through physicochemical characterisation

The work describes the physicochemical analysis of the water samples collected from Lahore Canal to evaluate pollution load at different points of the canal. Different physical and chemical pollutants such as temperature, pH, electrical conductivity, total dissolved and suspended solids, turbidity, chlorides, sulphates, nitrates, oils and grease, dissolved oxygen, chemical oxygen demand and biological oxygen demand (BOD) were analysed. The data was analysed through analysis of variance, which showed that the p values for dissolved oxygen (DO), chemical oxygen demand (COD), BOD, electrical conductivity, total dissolved solid (TDS), total suspended solid (TSS), turbidity, oil and grease, sulphates, and nitrates are <0.05, while p value of temperature, pH, and chlorides are 1.000, 0.984, and 0.070, respectively, which are >0.05. Further regression analysis revealed that the simple line regression modal is fit for turbidity and TSS, electrical conductivity and TDS, COD and DO, BOD and DO, and BOD and COD. The studies reveal that Lahore Canal is receiving a considerable amount of physical and chemical pollutants at different points.