Bacteriological, virological and chemical evaluation of a wastewater-aquaculture system

Levels of fecal coliforms (FC), fecal streptococci (FS), Salmonella spp and enteric viruses were monitored in the water, sediment and fish in experimental wastewater-fish ponds near Benton, Arkansas, U.S.A. Concentrations of five heavy metals were also monitored in the fish and wastewater. Concentrations of indicator bacteria were reduced by as much as 99.7% through the series of six ponds which had a calculated total retention time of 72 days. Two filter-feeding species of Chinese carp, Hypophthalmichthys molitrix (silver carp) and Aristichthys nobilis (bighead carp), grown in the last three ponds accumulated FC and FS in their digestive tracts and skin at levels as great or greater than in the surrounding water and sediment. Only low levels of FC and FS were found in the fish muscle tissue (maximum of 25 FS per 100 g) even when concentrations of bacteria in the gut exceeded 10⁵ per 100 g. Concentrations of bacteria in the water and sediment were not good predictors of concentrations in the fish. No Salmonella and no enteric viruses were isolated from the fish, but this lack of isolates was attributed to the extremely low levels which were present in the influent wastewater. Higher levels of copper and mercury were found in the fish flesh than in the surrounding water, with three of eleven fish samples containing higher than acceptable levels of mercury in the edible portion. Based on the efficiency of wastewater treatment, an aquaculture system using silver and bighead carp was judged to be a viable treatment system for domestic sewage resulting in a product suitable for animal or human consumption if proper precautions are taken in harvesting and processing the fish.     

Simultaneous determination of microcystin contaminations in various vertebrates (fish, turtle, duck and water bird) from a large eutrophic Chinese lake, Lake Taihu, with toxic Microcystis blooms

This is the first to conduct simultaneous determination of microcystin (MC) contaminations in multi-groups of vertebrates (fish, turtle, duck and water bird) from Lake Taihu with Microcystis blooms. MCs (-RR, -YR, -LR) in Microcystis scum was 328 μg g^− 1 DW. MCs reached 235 μg g^− 1 DW in intestinal contents of phytoplanktivorous silver carp, but never exceeded 0.1 μg g^− 1 DW in intestinal contents of other animals. The highest MC content in liver of fish was in Carassius auratus (150 ng g^− 1 DW), followed by silver carp and Culter ilishaeformis, whereas the lowest was in common carp (3 ng g^− 1 DW). In livers of turtle, duck and water bird, MC content ranged from 18 to 30 ng g^− 1 DW. High MC level was found in the gonad, egg yolk and egg white of Nycticorax nycticorax and Anas platyrhynchos, suggesting the potential effect of MCs on water bird and duck embryos. High MC contents were identified for the first time in the spleens of N. nycticorax and A. platyrhynchos (6.850 and 9.462 ng g^− 1 DW, respectively), indicating a different organotropism of MCs in birds. Lakes with deaths of turtles or water birds in the literatures had a considerably higher MC content in both cyanobacteria and wildlife than Lake Taihu, indicating that toxicity of cyanobacteria may determine accumulation level of MCs and consequently fates of aquatic wildlife.     

Determination of trace levels of linear alkylbenzenesulfonates in the marine environment by high-performance liquid chromatography

The widespread and increasing use of linear alkylbenzenesulfonates (LAS) has shown the need for analytical procedure of LAS. A method has been developed to isolate, concentrate and determine trace levels of LAS from marine environmental samples. LAS were extracted with Bond Elut C₁₈ reversed-phase minicolumn and quantified by high-performance liquid chromatography with fluorophotometric detection. This method can determine trace levels of LAS, simply, rapidly, specifically and sensitively and minimize the risk of contamination. This method showed the limit of determination for each LAS component of approx. 0.1 μg l⁻¹ for water, 0.03 μg g⁻¹ (dry basis) for bottom sediment or 0.3 μg g⁻¹ (wet basis) for fish sample, the recovery of 80% for water, 87% for sediment or 86% for fish sample, and the reproduceability of 3–4% relative standard deviation for five-replicated analysis of sea water or sea sediment.This proposed method was employed for the determination of LAS in marine environmental samples of Tokyo bay, Japan. A concentration range between 0.8 and 30 μg l⁻¹ of LAS was found in Tokyo bay water. The highest concentration was detected in the coastal areas.     

Cultivation of anaerobic granular sludge in UASB reactors with aerobic activated sludge as seed

Methanogenic bacteria of 10⁸ g SS⁻¹ in the activated sludges from an aeration tank treating sewage and from a secondary sedimentation tank of an activated sludge plant treating textile dyeing wastewater were enumerated by the Most Probable Number (MPN) technique. By using the two activated sludges as the seed material, anaerobic granular sludges were obtained at 35°C in two lab-UASB reactors having volumes of 29 and 481, and treating a glucose molasses solution of 1000–3500 mg COD 1⁻¹ and citrate wastewater of 20,000–36,000 mg COD 1⁻¹ respectively. The characteristics of granulation using the activated sludge as the seed were similar to those using digested sewage sludge as the seed. It is shown that activated sludge is readily available seed material for an anaerobic reactor. The growth of methanogenic bacteria in the activated sludge can be attributed to the existence of some anaerobic nuclei in the activated sludge flocs. The factors for the cultivation of granular sludge by using the activated sludge are also discussed.     

Algal settling ponds contribute to final effluent quality of integrated algal pond systems for municipal sewage treatment

Appropriate wastewater technologies and sound management are crucial to global water quality and conservation. The integrated algal pond system (IAPS), considered an efficient, passive and low-cost wastewater treatment technology for peri-urban spaces, is perceived to yield a final effluent unsuitable for discharge. Experiments were carried out to challenge the prevailing perception that algal-based wastewater treatment processes and in particular IAPS produce an effluent that does not always meet national and/or regional regulatory standards. Formation of a microalgal–bacterial floc (MaB-flocs) and settleability together with biomass removal from algal settling ponds (ASPs) is shown to reduce total suspended solids (TSS) from >50 to <20 mg L⁻¹. Thus, production of a readily settleable MaB-floc coupled with removal of settled biomass from ASP ensures that final effluent TSS remains below the general limit of 25 mg L⁻¹ and yields an effluent suitable for either irrigation or discharge.     

Water purification by fluidized bed technique

Composite samples of wastewater obtained from a Nigerian Institution were clarified with a 10% solution of commercial alum and then filtered through a sand bed. The optimum dosage for the clarification was 400 mg 1⁻¹. Considerable reductions in colour, turbidity, suspended solids (SS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), detergents of alkyl benzene sulphonate (ABS) base and total coliform bacteria were achieved in the samples.The samples were further purified by adsorption of their impurities by powered activated carbon (PAC) in a fluidized bed. The purification was done by two modes: fluidization with no beads added and fluidization with beads added. With 200 mg 1⁻¹ PAC and fluidization for 10 min, 92.8% COD reduction was achieved with no beads added while 98.5% COD reduction was achieved with 4% (v/v) glass beads added. Fresh surface water samples obtained from a dam were filtered through sand bed and similarly treated with 200 mg 1⁻¹ PAC in the fluidized bed. The qualities of the final effluents obtained from the two types of samples were comparable with the WHO standards for purified water/wastewater meant for recycling purposes.     

Bacterial response to a shock load of nanosilver in an activated sludge treatment system

The growing release of nanosilver into sewage systems has increased the concerns on the potential adverse impacts of silver nanoparticles (AgNPs) in wastewater treatment plants. The inhibitory effects of nanosilver on wastewater treatment and the response of activated sludge bacteria to the shock loading of AgNPs were evaluated in a Modified Ludzack-Ettinger (MLE) activated sludge treatment system. Before shock-loading experiments, batch extant respirometric assays determined that at 1 mg/L of total Ag, nitrification inhibitions by AgNPs (average size = 1-29 nm) and Ag⁺ ions were 41.4% and 13.5%, respectively, indicating that nanosilver was more toxic to nitrifying bacteria in activated sludge than silver ions. After a 12-h period of nanosilver shock loading to reach a final peak silver concentration of 0.75 mg/L in the MLE system, the total silver concentration in the mixed liquor decreased exponentially. A continuous flow-through model predicted that the silver in the activated sludge system would be washed out 25 days after the shock loading. Meanwhile, a prolonged period of nitrification inhibition (>1 month, the highest degree of inhibition = 46.5%) and increase of ammonia/nitrite concentration in wastewater effluent were observed. However, nanosilver exposure did not affect the growth of heterotrophs responsible for organic matter removal. Microbial community structure analysis indicated that the ammonium-oxidizing bacteria and nitrite-oxidizing bacteria, Nitrospira, had experienced population decrease while Nitrobacter was washed out after the shock loading.     

Nitrification in porous media during rapid,unsaturated water flow

A substantial nitrification in rapid infiltration (RI) systems for wastewater treatment is a prerequisite for obtaining good N removal by denitrification. The purpose of this study is to investigate nitrification in porous media at conditions corresponding to RI treatment systems. Nitrification in six 50-cm porous media columns (98% weathered granite or sand and 2% field soil) during unsaturated leaching at constant flow rates of synthetic wastewater was investigated. Concentrations of NH₄-N between 20 and 60 mg l⁻¹ were applied and vertical concentration profiles of NO₃-N, NO₂-N and NH₄-N were measured for 54 d at 30°C (three columns) and for 140 d at 10°C (three columns). A time lag in nitrification of 20 d was found at 10°C. Complete nitrification was obtained after 3–5 at 30°C and after approximately 50 d at 10°C. Assuming first-order nitrification at steady-state, the corresponding first order reaction rate coefficients (k₁) for NO₃ production in the columns were estimated to be between 0.4 and 1 h⁻¹ at 10°C and between 6 and 9 h⁻¹ at 30°C. Steady-state NO₃ profiles were obtained between 1.5 and up to 9 weeks after the experiments were started. At the actual soil-air contents (0.10 cm³ air phase cm⁻³ soil), oxygen limitations were not observed during the experiments. Nitrogen loadings (water flow times N concentration) above 100 mg N 1⁻¹ cm h⁻¹ (1 g N m⁻² h⁻¹) caused NH₄ accumulation in the columns at 10°C and should probably be avoided during operation of RI system.     

Avoidance-preference reactions of rainbow trout (Salmo gairdneri) after prolonged exposure to chromium(VI)

Avoidance-preference reactions were studied in rainbow trout (Salmo gairdneri) pre-exposed for 7–20 weeks to potassium dichromate solutions (K₂Cr₂O₇) ranging from 0.01 to 3.0 mg l⁻¹ as Cr(VI). Experiments were performed in a hydraulic channel 9.15 m long by 30 cm wide, partly divided along its length and at a flow depth of 30 cm, combining steep and shallow gradient characteristics. An avoidance threshold value of 0.028 mg l⁻¹ was determined for a population which had not been previously exposed to chromium while avoidance thresholds for pre-exposed fish increase linearly with the level of pre-exposure. Pre-exposed fish exhibited lower avoidance reactions compared to the nonexposed population. Avoidance reactions decreased with increasing level of pre-exposure. Fish exposed to test concentrations matching their pre-exposure level clearly preferred this same concentration over any adjacent lower or higher test concentration. After 7 days of acclimation in clear water fish previously exposed at 0.01–0.8 mg l⁻¹ Cr(VI), behaved similarly to the nonexposed population, indicating functional recovery of chemoreceptive capacity, while fish pre-exposed beyond the 0.8 mg l⁻¹ level did not recover fully within the same 7 day acclimation period. The 0.8 mg l⁻¹ Cr(VI) level is proposed as a critical pre-exposure level for short term recovery of normal chemoreceptive capacity. Times of pre-exposure within the range used for the study had no influence on avoidance reactions.     

Norovirus and FRNA bacteriophage determined by RT-qPCR and infectious FRNA bacteriophage in wastewater and oysters

Norovirus (NoV), the leading cause of adult non-bacterial gastroenteritis can be commonly detected in wastewater but the extent of NoV removal provided by wastewater treatment plants (WWTPs) is unclear. We monitored a newly commissioned WWTP with UV disinfection on a weekly basis over a six month period for NoV using RT-qPCR and for FRNA bacteriophage GA using both RT-qPCR (total concentration) and a plaque assay (infectious concentration). Mean concentrations of NoV GI and GII in influent wastewater were reduced by 0.25 and 0.41 log₁₀ genome copies 100 ml⁻¹, respectively by the WWTP. The mean concentration of total FRNA bacteriophage GA was reduced by 0.35 log genome copies 100 ml⁻¹ compared to a reduction of infectious FRNA bacteriophage GA of 2.13 log PFU 100 ml⁻¹. A significant difference between concentrations of infectious and total FRNA bacteriophage GA was observed in treated, but not in untreated wastewaters. We conclude that RT-qPCR in isolation underestimates the reduction of infectious virus during wastewater treatment. We further compared the concentrations of infectious virus in combined sewer overflow (CSO) and UV treated effluents using FRNA bacteriophage GA. A greater percentage (98%) of infectious virus is released in CSO discharges than UV treated effluent (44%). Following a CSO discharge, concentrations of NoV GII and infectious FRNA bacteriophage GA in oysters from less than the limit of detection to 3150 genome copies 100 g⁻¹ and 1050 PFU 100 g⁻¹ respectively.     

The use of Pb/210Pb ratios in lake sediments for estimating atmospheric fallout of stable lead in South-Central Ontario,Canada

The ratio of Pb concentrations (μg g⁻¹) to excess ²¹⁰Pb (²¹⁰Pb_exc) activities (dpm g⁻¹) in the surface (0–1 cm) sediments of lake cores, together with a knowledge of atmospheric ²¹⁰Pb fluxes, were used to estimate the atmospheric deposition of stable Pb in south-central Ontario, Canada. Between three and five cores were collected from each of 10 lakes, while in one lake (Red Chalk - Main Basin) a total of 25 cores were obtained.The average atmospheric ²¹⁰Pb_exc flux to the main basin of Red Chalk Lake was calculated to be 1.1 dpm cm⁻² year⁻¹, a value which compares favourably with literature estimates of ²¹⁰Pb deposition for Ontario. The surface Pb/²¹⁰Pb_exc ratios for 61 cores ranged between 1.26 and 3.44 μg dpm⁻¹(average 2.15 ± 0.45 μg dpm⁻¹). Therefore, the predicted atmospheric Pb deposition was 14–38 mg m⁻² year⁻¹ (average 24 ± 5.0 mg m⁻² year⁻¹). This estimate of stable Pb fallout is similar to those measured by alternate methods and indicates that elemental ratios in lake sediments might be useful for predicting the behaviour of other contaminants in lakes.     

Biological treatment of a coal gasification process wastewater

An 8 month experimental study was performed to assess biological treatability characteristics of Hygas coal gasification process pilot plant wastewater comprised of cyclone and quench condensates. The study evaluated treatability characteristics of ammonia stripped and unstripped wastewater at full strength and at 1:1 dilution. It was determined that minimum pre-treatment required for biological oxidation consisted of reducing wastewater alkalinity, and decreasing raw ammonia concentration by dilution or by stripping. Kinetic studies with stripped Hygas wastewater showed the waste could be processed at mean cell residence times varying from 10 to 40 days with hydraulic residence times of 2–3 days; the bacteriological yield coefficient was 0.10 (COD basis), and the decay coefficient was 0.01 day⁻¹. Hygas wastewater seemed to inhibit bacteriological growth because mean cell residence times less than 10 days do not appear feasible and because apparently higher yield coefficients were observed with diluted wastewater. However, this factor should not effect removal efficiencies for organic contaminants at recommended processing conditions.     

Bioaccumulation profiles of 35S-labelled sodium alkylpoly(oxyethylene) sulfates in carp (Cyprinus carpio)

The uptake, distribution and elimination of two labelled surfactants, ³⁵S-labelled sodium dodecyltri(oxyethylene) sulfate (³⁵S-C12-AES(3)) and ³⁵S-labelled sodium dodecylpenta(oxyethylene) sulfate (³⁵S-C12-AES(5)) were investigated in carp (Cyprinus carpio) exposed to concentrations of 0.3–0.6 mg l^?1, using whole-body autoradiography and the liquid scintillation counting method. ³⁵S-Radioactivity was first rapidly absorbed by the gills and skin and transferred to other organs and tissues. After 24 h-exposure, there was a comparatively high accumulation of ³⁵S-radioactivity in the gills, hepatopancreas, gall bladder, intestinal content, and nasal and oral cavity. The distribution patterns of ³⁵S-radioactivity derived from ³⁵S-C12-AES(3) and ³⁵S-C12-AES(5) in tissues and organs were similar. The whole-body concentration factors of ³⁵S-radioactivity in fish exposed to ³⁵S-C12-AES(3) and ³⁵S-C12-AES(5) for 72 hr were 18 and 4.7, respectively. In surfactant-free water, the absorbed ³⁵S-radioactivity was eliminated more rapidly from the fish body exposed to ³⁵S-C12-AES(3) than ³⁵S-C12-AES(5). It was eliminated relatively fast from gills and hepatopancreas, but elimination from gall bladder was rather slow.     

Interactions between methanogenic,sulfate-reducing and syntrophic acetogenic bacteria in the anaerobic degradation of benzoate

Effect of sulfate on the anaerobic degradation of benzoate was investigated by using the chemostat-type reactors at 35°C. The benzoate concentrations were equivalent to 1250–10000 mg.l⁻¹ in COD (chemical oxygen demand) and the sulfate concentrations were equivalent to 167–1670 mg.l⁻¹ in sulfur (S). Interactions between the methane-producing bacteria (MPB) and sulfate-reducing bacteria (SRB) were dependent strongly on the ratio of COD/S in wastewater. The MPB consumed 99% of the available electron donors at COD/S ratio of 60, but consumed only 69% at ratio of 1.5, and 13% at 0.75. The biochemical reactions and the bacterial composition in the biomass were also governed by the COD/S ratio. At high COD/S ratios (3.0 or higher), benzoate was degraded mainly to methane via acetate and hydrogen/formate. The degradation of benzoate required the syntrophic association between the hydrogen-producing acetogens such as Syntrophus buswellii and hydrogen-consuming MPB, plus Methanothrix-like MPB. On the other hand, at low COD/S ratio (1.5 or lower), benzoate was consumed mainly by SRB, converting sulfate into sulfide and suppressing the methane production. The anaerobic degradation of benzoate was partially inhibited when sulfide concentration was high.     

Lead in coastal sediments: The case of the elefsis gulf,Greece

Lead was determined in surface sediments and cores of a typical, polluted, almost enclosed Mediterranean embayment, the Gulf of Elefsis, near Athens. Total lead concentrations of 500–600 μg g⁻¹ were found in the surface sediments of the northeast section of the gulf, near major industries. However, a few kilometers from the source the concentrations decrease to ∼ 40m μg g⁻¹; the background pre-industrial levels are ∼ 10 μg g⁻¹ (in the < 61 μm fraction). Sequential extractions, consideration of the Pb/Al and Pb/Zn ratios, etc., indicate that the upper 5–15 cm of the sediment column are greatly enriched with lead of anthropogenic origin, which is mainly associated with fine particles. Redox reactions play an important role in the distribution and chemistry of lead, most of which (∼ 40%) is associated with organic matter and sulphides (extracted by EDTA); another ∼ 30% is associated with iron and manganese coatings and carbonates, with only a small but significant 3–4% of the total in a readily exchangeable form. The latter, under given conditions, may influence the lead concentrations in the overlying waters.     

Septage disposal in waste recycling ponds

Experiments were carried out to investigate the feasibility of septic tank sludge (septage) disposal into pilot-scale waste recycling ponds for the production of algae and fish. A septage loading of 100 kg COD ha⁻¹ day⁻¹ to four 4-m² single-stage ponds resulted in the production of algal biomass and dissolved oxygen in the pond water, suitable for Tilapia growth. Some microbiological investigations of this waste recycling scheme were undertaken using ten earth ponds (each with the dimensions of 20 × 10 × 1.3 m: length × width × depth). It was found that the densities of coliform bacteria and bacteriophages in the pond water and sediment tended to increase with increased septage loadings and loading periods. The ponds fed with septage at the loading of 100 kg COD ha⁻¹ day⁻¹ were found to contain higher densities of these microorganisms than those of the control pond without septage feeding. The possible public health impact resulting from this practice was assessed.     

Biological oxidation of high strength nitrogenous wastewater

A nitrification study was conducted in continuous flow stirred tank reactors using high strength nitrogenous wastewater (concentrated stream from a urea plant mixed with pharmaceutical wastewater). The reactors were operated at different solids retention times (SRT = 10–62.5 d) and hydraulic retention times (HRT = 1.5–2.1 d). Pharmaceutical wastewater was used as an organic carbon source to maintain a COD/TKN ratio of 1. The nitrification achieved at different SRTs varied from 87 to 99%. The nitrogen balance data show that ammonia assimilation and denitrification accounted for 4–53% of the total nitrogen removed. The yield coefficients and decay coefficients were Y_b = 0.5 (COD basis), k_db = 0.07 d⁻¹ (COD basis) for heterotrophs and Y_n = 0.15 (TKN basis), k_dn = 0.06 d⁻¹ (TKN basis) for nitrifiers respectively.     

Calcium phosphate precipitation in a fluidized bed in relation to process conditions: A black box approach

The precipitation features of calcium phosphate in a fluidized bed reactor in the concentration range between 5 and 100 mg P 1⁻¹ were studied, and the conditions for optimum phosphate removal efficiency were established. The supply of calcium ions should be such that a Ca/P molar ratio of 3 at the inlet of the reactor is achieved. If the water to be treated does not contain magnesium or carbonate ions, the supply of base should suffice to promote a conversion of 50–65% of the incoming phosphate to the solid phase. In the presence of carbonate and magnesium ions, the base supply should provide a conversion of 80–95%. Magnesium and carbonate ions did not have a detrimental effect on the phosphate removal efficiency for inlet concentrations of up to 4.8 × 10⁻³ (Mg/P < 2 mol mol⁻¹) and 1.8 × 10⁻³ kmol m⁻³, respectively. The feasibility of a process based on the precipitation of magnesium phosphate instead of calcium phosphate was demonstrated for waters with a low calcium content (Ca/P < 0.8 mol mol⁻¹). Finally a method is presented to select process conditions where co-precipitation of unwanted phases can be avoided.     

Absence of acclimation to parathion by rainbow trout during sublethal exposure

After 1, 2, 3 and 5 weeks of pre-exposure to 0.31 mg l⁻¹ of parathion, rainbow trout (Salmo gairdneri) did not change their tolerance of lethal levels of the organophosphate insecticide. This pre-exposure concentration represents 0.25 of the mean control incipient lethal concentration. Thresholds of lethality were reached at 120–144 h for all lethal tests though mortality commenced 12–24 h earlier in lethal tests using pre-exposed fish. Both groups grew during the pre-exposure, but dry weight of pre-exposed fish was only 0.75 of control weight at the end of the pre-exposure. Parathion pre-exposed fish also showed reduced appetite and activity.     

Elemental mercury contamination survey in a chlor-alkali plant by the use of transplanted Spanish moss,Tillandsia usneoides (L.)

Atmospheric Hg⁰ contamination and the potential risk of occupational exposure were evaluated in a chlor-alkali facility by the use of transplanted Tillandsia usneoides. This plant species was selected since it presents some features that makes it useful for air monitoring purposes. After short-term exposure (15 days), control plants showed a mean concentration of 0.2 μg Hg.g⁻¹ whereas Hg values in transplants ranged from 1 to 10 400 μg.g⁻¹. This latter value was observed near an elemental Hg spillage. Even after exposure to toxic conditions plant metabolism was still operative, allowing the transplant technique to be employed to assess both Hg taken up through the stomata and Hg associated with particles deposited on the biomonitor.