Fishpond Effluents Research Articles

Impacts of fish pond effluent on the water quality of an afrotropical stream: a comprehensive evaluation using the water quality index

This study highlights the importance of managing fishpond effluent to minimize its impact on aquatic environments. Fish effluents are a major concern worldwide in aquatic environments. It also provides information on the impacts of effluents on the water quality index of streams when released into aquatic environments. Streams and fishponds were sampled bimonthly for two annual cycles, covering different sampling stations both upstream and downstream of the fishpond effluents at 50-m intervals. Water quality parameters associated with in situ conditions were determined in the field. In the laboratory, other physicochemical parameters were determined via proper standard protocols. The results of the study revealed that water quality parameters such as turbidity, total suspended solids, total solids, conductivity, total dissolved solids, dissolved oxygen, biological oxygen demand and organic matter recorded in water samples collected from 50 m upstream at the point of effluent discharge were significantly (p < 0.05) different from those recorded at other sampling stations. The WQI value of the discharge point was higher than the WQI recorded in both the upstream and downstream sections of the stream. The findings of this study showed that the point of discharge of fishpond effluents is particularly concerning for the receiving stream compared with other sampling points. This localized area has experienced marked deterioration in water quality, posing significant threats to the health and biodiversity of aquatic ecosystems. The effluent's impact, though slight when dispersed in the receiving waterbody, underscores the necessity for adequate management practices to mitigate its adverse effects. Effective strategies, including regular monitoring, effluent treatment, and sustainable pond management, are imperative to ensure the long-term health and resilience of the aquatic environment.

Effects of Effective-Microorganism (EM) Treated Fish Pond Effluent on Soil Microbial Activities

An experiment was conducted at the Department of Crop/Soil Science, Rivers State University to evaluate effects of Effective Microorganism (EM) treated fish pond effluent on soil microbial activities. The study had two levels of fish pond effluent (Diluted and undiluted) and three levels of treated effluent (0EMAS, EMAS, EMAS+EM5) laid out in a completely randomized design with three replications. Microbial count and Carbon-dioxide evolution were evaluated. Total Carbon-dioxide evolved after 15 weeks was highest in soils treated with EMAS+EM5-N and was least in EMAS+EM5-D. The identified fungal isolates were Aspergillus and Mucor species, and the identified bacteria were Bacillus and Micrococcus species but bacteria were more predominant than fungi and recorded highest in soils treated with EMAS+EM5-N. Also Effective Microorganism (EM) increased the biodiversity of microorganism. Data were subjected to analysis of variance.

Evaluation of antibiotic use patterns among farmers and antibiogram from livestock wastes and fish pond effluents in selected animal farms in Cross River State, Nigeria

The extensive and misuse of antibiotics in animal production has become a public health threat. The evaluation of antibiotic use pattern among farmers and antibiogram from livestock wastes and effluent from animal farms was conducted in Cross River State. A descriptive cross-sectional study was undertaken with 379 animal production farmers and multi-stage sampling technique was employed in the selection of farms and respondents. Bacteriological analysis of animal wastes samples and antibiotics susceptibility testing was also conducted. Results revealed that 66.8% of farmers had a good knowledge on the use of antibiotics and its resistance. Majority (91.0%) of the farmers used antibiotics in their animal farms and for purposes of growth promotion, treatment of disease and prevention. Tetracycline, ampicillin, streptomycin, cotrimoxazole, gentamycin and vancomycin were the most frequently used groups of antibiotics. A total of 240 bacteria were isolated and the percentage occurrence of bacterial isolates were: Pseudomonas aeruginosa (14.2%), Escherichia coli (12.5%), Staphylococus aureus (10.8%), while Staphylococcus hominis (2.1%) had the least prevalence of occurrence. All the isolates showed multi-drugs resistance, Staphylococcus aureus showed the highest resistance to several antibiotics commonly used by farmers (80.8% to chloramphenicol, 80.8% to vancomycin and 73.1% of resistance to tetracycline). Statistical analysis of sociodemographic variables with farmers’ knowledge and antibiotics use showed that respondents’ level of education, years of farming experience, and farm type, were statistically significant (p&lt;0.05). There is a need to improve farmers’ knowledge of antibiotics use and the possible consequences of their inappropriate use of antibiotics in farms.

Development of Ag-doped on multi-walled carbon nanotubes for the treatment of fish pond effluent

The treatment of fish pond wastewater utilizing nanocomposites by batch adsorption using purified carbon nanotubes and silver-doped carbon nanotubes (CNTs) as nano-adsorbents was explored in this study. Ultraviolet spectroscopy, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM) were used to confirm the biosynthesized AgNPs. The metallic silver is associated with the peaks in the XRD pattern, and HRTEM studies indicated that AgNPs are between particle sizes of 11.12 and 15.39 nm. Purified carbon nanotubes (P-CNTs) and silver-doped carbon nanotubes (Ag-CNTs) were produced using a Fe–Ni/kaolin catalyst in a catalytic chemical vapour deposition process, followed by acid purification and doped with silver nanoparticles, respectively. HRTEM, HRSEM, FTIR, and BET were used to characterize the as-synthesized CNTs, P-CNTs, and Ag-CNTs. Both unpurified and purified CNTs were tube-like, extremely porous, and crystalline, with Ag-CNTs having a higher surface area (1068 m2/g) greater than P-CNTs (268.40 m2/g). The batch adsorption process was used to investigate the adsorption behaviour of P-CNTs and Ag-CNTs to remove Fe, Mn, and Zn from fish pond effluent as a function of contact time, adsorbent dosage, and temperature. The Freundlich isotherm described equilibrium sorption data better than the Langmuir isotherm, and the adsorption kinetics fit well with the pseudo-second-order model. A thermodynamic study of the adsorption process found that the change in Gibbs free energy was negative, indicating that the adsorption process was feasible and spontaneous. Consequently, it has been demonstrated that removing heavy metals from aquatic effluent using Ag-doped CNTs is effective in aquaculture.

Predicting selected kinetic parameters of hydrocarbon interactions with alum-based water treatment residuals

Kinetic parameters of hydrocarbon interactions with alum-based water treatment residuals (WTR) in the biostimulation of crude oil-polluted soil are very important because they reveal how long the WTR bind with the hydrocarbon to control its fate and transport in the soil. In this study, we used Michaelis-Menten biokinetic model to determine two important kinetic parameters, the maximum specific rate constant (μmax) and Michaelis-Menten constant (Km), as well as total petroleum hydrocarbon (TPH) degradation rate equation in the biostimulation of crude oil-polluted Niger Delta Oxisols using WTR synthesized from local fishpond effluents. Using the completely randomized design, the experimental setup consisted of 6-duplicate reactors including the control (labelled A to F) containing mixtures of soil, crude oil, and WTR in the ratios of 4:1:0, 4:1:1, 4:1:1.5, 4:1:2, 4:1:2.5, and 4:1:3, respectively. Treatment lasted for 70 days and TPH concentration was determined by gas chromatography-mass spectrometry (GC-MS). Results showed that a rounded average of 51% TPH reduction was achieved after 70 days of treatment. The rounded average of μmax was 0.5 mg/kg-day and Km was 270 mg/kg, while the TPH degradation rate equation was deduced as r=−0.5S/(270+S) at any TPH concentration, S. With an average root-mean-square error of 4.998 mg/kg, residual prediction deviation of 18.08, and corresponding validation r2 of over 99%, the model prediction was categorized as excellent with an error of only 1%. This shows the potential of the model to predict TPH in the biostimulation of crude oil-polluted Niger Delta Oxisols with alum-based WTR.

Growth, biofiltration and photosynthetic performance of Ulva spp. cultivated in fishpond effluents: An outdoor study

Anthropogenic impacts on water resources, especially by ​​nutrient discharge, is a worldwide problem in marine coastal areas. In this context, seaweed cultivation in aquaculture wastewater can be considered as an alternative for effluent mitigation, where the biomass becomes a source of valuable compounds. The current study examined the potential use of the seaweeds Ulva pseudorotundata and Ulva rigida to remove nutrients to treat effluents from the culture of Chelon labrosus. Two experiments were conducted under pilot-scale conditions to evaluate the nutrient uptake, photosynthetic activity, and biomass production of the seaweed species cultivated under 50 and 100% effluent concentrations. Photosynthetic parameters were determined by in vivo chlorophyll a fluorescence associated to photosystem II 3 times a day to estimate photosynthetic performance and seaweed physiology throughout the experiment: optimal quantum yield (Fv/Fm), in situ and ex situ electron transport rate (ETR), photosynthetic efficiency (αETR), saturation irradiance (Ek), and the maximum non-photochemical quenching (NPQmax). To evaluate seaweed metabolism and biomass compounds, elemental and biochemical composition were analyzed in the beginning and end of each experiment. Results regarding the nutrient source showed that both species removed more than 65% of ammonium after 3 hours of experimentation. At the end of the experiments, up to 94.8% of the initial ammonium was sequestered from the effluent. Additionally, after 5 days of cultivation under 50% fish effluent both Ulva species were able to remove more than 85% of the nitrate. Although a decrease in uptake efficiency was observed in cultures with 100% fish effluent, at the end of the experiment more than 440 µmol L-1 of nitrate was removed, considering all treatment conditions. The biomass values showed that growth rates of seaweed cultivated in 100% effluent were higher than those obtained in 50% effluent. Moreover, when cultivated in the 100% effluent concentration, a significant increment in protein content was detected in both Ulva species. Our results contribute to the understanding of biofiltration and photosynthetic performance of two different Ulva species in order to improve growth optimization, enhancement of biofiltration capacity and also to boost management practices of seaweed cultivation in aquaculture effluent treatment systems.

Bacteriological and Physicochemical Analysis of Fish Pond Effluents in Warri and Its Environs, Nigeria

Aims: This study was to ascertain the bacteriological and physicochemical characteristics of fish pond effluents.&#x0D; Study Design: Waste water samples were collected from six (6) different ponds, three (3) earthen ponds (A, B &amp; C) and three (3) concrete ponds (D, E &amp; F).&#x0D; Place and Duration of Study: The study was conducted in a laboratory in the Department of Environmental Management and toxicology, Federal University of Petroleum Resources, Effurun, Delta State, Nigeria. The research lasted for six months.&#x0D; Methodology: Standard procedures were adopted for sample collection, microbiological and physicochemical analyses. Waste water samples were analyzed for total bacterial count, total coliform count and Escherichia coli (E. coli) count. Physicochemical parameters measured were pH, electrical conductivity (EC), dissolved oxygen (DO) and temperature and many others.&#x0D; Results: Pond C which was an earthen pond was found with the highest bacterial, coliform and E. coli. counts (2.8 × 105 ±0.01, 1.2 × 103 ±0.10 and 0.5 ×102 ±0.04 cfu/ml), and pond F, a concrete pond, recorded the lowest bacterial and coliform counts of (2.3 × 104 ±0.05, 0.2 × 103 ±0.00 cfu/ml respectively and insignificant E. coli count. The isolated bacteria species were Lactobacillus sp., E. coli, Klebsiella sp., Staphylococcus sp., Streptococcus sp., Enterobacter sp. and Proteus sp. The occurrence of the isolated bacteria was highest in pond C with 71.43%. The values of turbidity and total hardness were above WHO and FEPA standards, while values of other physicochemical characteristics complied with WHO and FEPA standards. The antibiotics susceptibility test of the bacterial isolates revealed multiple antibiotics resistance.&#x0D; Conclusion: The study revealed that these ponds were disgustingly infected with pathogenic bacteria that could affect cultured fishes by causing diseases, lowering the fish yield and resulting into economic loss, threatening human’s health and contaminating the environment where the effluents are discharged into.

Preliminary Investigation of Microbial Community in Wastewater and Surface Waters in Sri Lanka and the Philippines

In this study, the composition and richness of bacterial communities in treated and untreated wastewater from hospitals, commercial, and non-commercial fish farming sites, sewage effluents, and surface waters, which included seawater and fresh water in Sri Lanka and the Philippines, were investigated through 16S rRNA gene amplicon sequence analysis. Firmicutes were found predominantly in Sri Lankan hospital wastewaters, while Cyanobacteria and Acidobacteria were typically detected in fish culture sites and the waste canal in Sri Lanka, respectively. The Shannon–Weaver index (SW) and number of Operational Taxonomic Units (OTUs) were higher in the Philippines than in Sri Lanka. The bacterial richness in the university non-commercial fish pond and sewage effluent displayed greater than that in hospital wastewaters. In addition, the bacterial richness was higher in the untreated wastewater compared to that in the treated wastewater in hospitals. These results indicate the differences among water types in terms of bacterial community, especially influenced by their source.

A study on physicochemical parameters of fish pond effluents: A case study of Umudibia fish farm

This study investigated the physicochemical characteristics of fish pond effluents. Four (4) effluent samples were collected at two-day intervals from a fish pond located at Umudiba Nekede, Owerri, and analyzed to ascertain their characteristics. The physiochemical parameters assessed are the temperature, biochemical oxygen demand, chemical oxygen demand, total dissolved solids, turbidity, ammonia, total hardness, alkalinity, pH, and electrical conductivity. The result revealed the following ranges for the physicochemical characteristics: temperature (23.0 to 25.9°C), pH (6.24 to 3.1), total alkalinity (43.1 to 50.4mg/l), total dissolved solid (27.9 to 95.2 mg/l), total hardness (19.7 to 21.5mg/l), turbidity (12 to 170 NTU), and electrical conductivity (137.6 to 144.3 μmhos/cm). The result of the study indicated that the effluents from the fish pond could constitute a threat to the ecology of the aquatic water bodies if not properly treated before discharge.

Effects of Sole and Combined Physical Filtration Materials on Physicochemical and Microbiological Properties of Waste Waters

Agricultural re-use of waste waters is a feasible alternative for increasing water resources for agriculture. Several methods have been adopted for improving waste water quality for safe re-use in agriculture. However, these methods are complex and difficult to use by local farmers. Hence, a study was conducted to examine the effects of a simple and cost-effective waste water treatment methods on physicochemical and microbial properties of waste waters. The research was conducted in the Department of Crop, Soil and Pest Management, the Federal University of Technology, Akure (FUTA). Waste waters consisted of: fish pond effluent and municipal stream. Materials used for physical filtration of waste waters include: granite, rice husk, charcoal, and pure river sand. Prior to and after treatments, the waste waters were subjected to chemical analysis (pH, electrical conductivity (EC), Nitrate, Cl, P, Ca, and Mg), physical analysis (Total solid, Total dissolved solid and Total suspended solid), and microbiological analysis (Total faecal coliforms, bacteria, yeast and fungi). Results obtained showed that sole and combined applications of physical filtration materials significantly reduced microbial loads in waste waters. Similarly, significant reductions in total solid (TS), total suspended solid (TSS) and total dissolved solid (TDS) were obtained for waters filtered with the filtration materials, both in the single and combined applications. The highest significant pH, EC and chloride were recorded in untreated fishpond effluent (T₁), while fishpond effluent filtered with rice husk (T₅) recorded the highest Significant Ca and Mg. Highest significant Nitrate was recorded in municipal wastewater filtered with rice husk (T₁₁), while highest significant P was obtained at T₅ and T₁₁. Results of this research showed improvement in the quality parameters of waste waters filtered with sole and combined filtration materials.

Evaluation of Luffa cylindrica fibres in a biomass packed bed for the treatment of fish pond effluent before environmental release

The aim of this study was to investigate the potential of Luffa cylindrica fibres in a packed bed for the treatment of fish pond effluent before releasing into the environment. The fibres were modified by mercerisation with 0.5 M NaOH solution. Both modified and unmodified fibres were characterised using Fourier transform infrared (FTIR) spectroscopy. Parameters measured were the pH, total dissolved solids (TDS), total suspended solids (TSS), dissolved oxygen (DO), chemical oxygen demand (COD) and biochemical oxygen demand (BOD). It was observed from the study that a biomass packed bed of modified and unmodified Luffa cylindrica fibres was unsuitable in remediating the DO, TDS and COD of fish pond effluents. However, the material was suitable in remediating the pH, TSS, BOD and colour of the fish pond effluents. The process reduced the colour from 9.83 to 7.12 TCU for the modified fibres and 3.41 TCU for the unmodified fibres. TSS was reduced from 2.92 to 2.8 mg/l for the modified fibres and 2.61 mg/l for the unmodified fibres. BOD was reduced from 3.5 to 0.6 mg/l for the modified fibres and 1.4 mg/l for the unmodified fibres.

An integrated, two-step biofiltration system with Ulva fasciata for sequenced removal of ammonia and nitrate in mariculture effluents

Secondary treatment of fishpond effluent is imperative for the removal of excess nitrate and phosphorus. Biofilters comprised of the green macroalgae, Ulva, exhibit several advantages for this process, including usability of the produced edible biomass. However, even low levels of ammonia in fishpond effluent inhibit the uptake of nitrate by Ulva. In order to overcome this drawback we examined Ulva faciata in a two-step biofiltration system. The biofiltration system comprised of two sequenced tanks where the upstream Ulva biofilter was fed directly with mariculture effluent containing both ammonia (as total ammonium nitrogen - TAN) and nitrate (as NO3-N) and the TAN-depleted but NO3-N-rich effluent from this biofilter were transferred to the downstream Ulva biofilter. The performance of each separate Ulva biofilter as well as that of the whole system was measured on a weekly regime over a culture period of three weeks. Between 81 and 95% of the dissolved inorganic nitrogen (TAN + NO3-N) in mariculture effluent was removed by the two-step biofilter, with specific removal of 89–100% of TAN and 57–78% of NO3-N in mariculture effluent by the upstream and downstream Ulva, respectively. Exposure of Ulva in upstream biofilters to higher N input with both TAN and NO3-N did not affect algal production rate, which was relatively similar to that in downstream biofilters fed with TAN-depleted, NO3-N-rich effluent, with mean specific growth rate of 17.85% d−1 (±3.1) in the different biofilters. Removal rates of TAN or NO3-N by upstream and downstream Ulva, respectively, were relatively similar, between 90 and 135 mmol N m−2 d−1, while PO4-P removal was much faster in downstream Ulva biofilters having only NO3-N as a N source. While TAN removal induced production of Ulva biomass with higher N, P and protein content, culture in NO3-N-rich effluent resulted in Ulva biomass with higher lipid content.

Adsorptive kinetics, isotherm and thermodynamic analysis of fishpond effluent coagulation using chitin derived coagulant from waste Brachyura shell

High grade chitin extracted from Brachyura shell waste was successfully used for adsorptive de-colorization of highly turbid fishpond effluent. Brachyura shell chitin was characterized via Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results obtained from the characterization indicated that the extracted chitin possessed significant features required for surface phenomenon driven matrices. The best efficiency obtained for turbidity and color removal were 88% and 91%, respectively, at BSC dosage of 1.8 g/L, pH of 6.0 and temperature of 45°C. The maximum adsorption capacity of the de-colorization process onto BSC was found to be 265.59 mg/g. Results from kinetic analysis suggested that pseudo-second order model was most accurate (R2 > 0.99) in predicting the experimental data. Webber-Morris intraparticle diffusion rate constant (Kipd) demonstrated that the adsorptive process depended more on film diffusion mechanism. Equilibrium study was carried out using Langmuir, Freundlich, Temkin, Dubinin Radushkevich and Brunauer-Emmett-Teller isotherm model at 30, 40 and 50°C. Fitness appraisal analysis of the isotherm models pointed out that experimental data aligned significantly with Langmuir and Temkin isotherm (R2 > 0.94), suggesting the homogenous and monolayer mode of the adsorptive process. Values of Gibbs free energy (− ΔG0= 1.7816 – 2.6706 kJ /mol), enthalpy (ΔH0= 11.6867kJ/ mol), activation energy (EA= 13.2330kJ/ mol) and entropy (ΔS0= 44.4511J / molK) obtained from thermodynamic analysis confirmed the spontaneous, endothermic, favorable and physical nature of the process.

Integrated biofilters with Ulva and periphyton to improve nitrogen removal from mariculture effluent

Biofilters composed of Ulva or periphyton reveal great potential in removal of excess nitrogen in mariculture effluent while producing protein-rich edible biomass. However, TAN depletion is requisite to improve nitrate removal performance. In the current study we compared the contribution of Ulva fasciata and periphyton in removal of nitrogen, particularly in the form of nitrate, from fishpond effluent. For this purpose, we integrated U. fasciata or periphyton as a secondary biofilter downstream to a primary U. fasciata biofilter, and measured growth and nutrient removal performance in each of these two-step biofilters and in their constitutuent biofiltration units. The upstream U. fasciata biofilters removed nearly all TAN from fishpond effluent, leaving less than 5 μM of TAN but excess NO3-N in the effluent leaving these biofilters for the downstream biofilters. The downstream U. fasciata biofilter removed 76% of NO3-N from its inlet water. While this was about three times more efficient than its periphyton counterpart, the periphyton's specific removal rate of this nutrient (1.5 g NO3-N g−1 DW d−1) was much faster than that of U. fasciata. Overall, integration of two sequenced U. fasciata biofilters (‘Ulva-Ulva’) yielded more biomass and removed more nitrogen than the Ulva-periphyton biofilter (removing 25 vs. 18 g N wk.−1, respectively). Despite the differences in N removal rate and efficiency, the protein level in upstream U. fasciata and downstream periphyton was relatively similar (~25% DW), while somewhat lower in the downstream U. fasciata. Results of the current study favour the two-step U. fasciata biofilter, but periphyton's faster specific removal of NO3-N and its contribution to oxygen generation should not exclude further improvement of this technology.

Effects of Biofilms on Ammonium Removal Efficiency in Fish Pond Effluents

Treatment of wastewater in fish ponds effluent is an effort to reduce the impact of pollutants contained in the wastewater so that it can be disposed into the aquatic environment safely. The purpose of this study is to understand and analyze the effect of inoculant sources on removing of total ammonium in vanamae shrimp and marguensis shrimp pond wastewater, and to pre-design the technology for treating high-salinity organic waste with biological wastewater treatment using natural microorganisms. The study was conducted using a laboratory-scale reactor. At the beginning of the study, adherent biofilm media was planted at the bottom of the sea with a depth of 1.5 m for three weeks to grow nitrifying bacteria, then applied to treat fish pond wastewater. The results showed that the efficiency of ammonium reduction with adherent media from Telukawur is 74% while adherent media from Panjang Island is 66% with declining and fluctuating trends every day. The extensive -scale application for treating wastewater from brackishwater aquaculture is designed with 4 processing units, a 15.5 m x 7.7 m x 1.5 m sedimentation basin, a 10.5 m x 3.5 m x 1.5 m anaerobic basin, a 13 m x 13 m x 1.5 m aerobic basin, and a 15.5 m x 7.7 m x 1.5 m effluent basin. It concludes that biofilm adhesion technology from Panjang Island waters and Telukawur waters can work efficiently in removing ammonium concentration.

Antioxidant activity of extracts from marine macroalgae, wild-collected and cultivated, in an integrated multi-trophic aquaculture system

Methanolic and hydroethanolic extracts of ten common species of marine macroalgae (5 Rhodophyta, 2 Ochrophyta and 3 Chlorophyta) of the intertidal system of the Canary Islands were screened to evaluate their in vitro antioxidant activity by DPPH radical scavenging activity and reducing power. The concentration of bioactives as pigments and phenolic compounds was also determined. Wild-collected algae and these cultivated in an integrated multitrophic aquaculture (IMTA) system during one month, were analyzed. The highest antioxidant activity was observed in Halopithys incurva, Fucus spiralis and Treptacantha abies-marina. The hydroethanolic extracts exhibited higher reducing power than methanolic extracts in most species. However, the differences in DPPH scavenging activity between solvents were not so high, and only the hydroethanolic extracts of some species showed antioxidant activity. The highest concentration of polyphenols was reached in H. incurva, T. abies-marina and F. spiralis. However, compared to collected seaweeds, the percentage of these compounds was lower in cultivated samples. The highest concentrations of chlorophyll a and carotenoids were found in T. abies-marina, Codium intertextum and F. spiralis. In red algae, the phycoerythrin (PE) content was higher in H. incurva, followed by P. capillacea. After culture, pigment content increased in most species, depending on the assimilation capacity of the ammonium from fishpond effluents. C/N ratio in samples collected in the field was high, indicating nitrogen limitation. After cultivation under high nitrogen availability (fishpond effluents), the ratio decreased in all species, especially in C. intertextum, F. spiralis and H. incurva, by the accumaltion of N-compounds. Pearson coefficient only showed significant correlations between the reducing power and some bioactive compounds, particularly polyphenols and PE. In conclusion, culture under IMTA conditions changed the biochemical composition of algae. The antioxidant activity did not decrease after culture in several species, despite the reduction of phenolic compounds, probably due to the benefits of the high N availability in the IMTA.

Effect of a reduced fertilizer rate on the water quality of paddy fields and rice yields under fishpond effluent irrigation

Aquaculture effluent irrigation has been widely adopted to replace freshwater irrigation to save water and providing additional fertilizer to the crop. There is limited information on the performance of fertilizer supply levels under fishpond effluent irrigation. The objectives of this study were to investigate the effect of reducing a rate of fertilizer on the purification of wastewater from fishponds by paddy fields and the yield of rice under fishpond effluent irrigation in central China in 2015. The treatments included 100 %, 80 %, and 60 % of the normal fertilizer rate (NFR, 150 kg N ha−1, 120 kg P2O5 ha−1 and 75 kg K2O ha−1) with fishpond (freshwater-pond aquaculture) effluent as an irrigation source, designated NFR-E, 0.8NFR-E, and 0.6NFR-E, respectively; with an additional NFR with freshwater as an irrigation source (NFR-F). The results showed that 5700 m3 ha-1 freshwater was saved by the use of the NFR-E, 0.8NFR-E and 0.6NFR-E treatments. The concentrations of total nitrogen (TN), total phosphorus (TP), dissolved phosphorus (DP), ammonia-nitrogen (NH4+-N), nitrate-nitrogen (NO3--N) and particulate phosphorus (PP) in the surface water and seepage water of the paddy field and the residual soil N and P in the 0−60 cm soil depth after the rice harvest decreased with the decreasing NFR. The removal rates of the TN in the surface water across the tillering, booting, heading and filling stages were 25.1 %, 38.9 % and 50.5 % on average for the NFR-E, 0.8NFR-E and 0.6NFR-E treatments, respectively. The corresponding removal rates of the TP were 56.4 %, 71.2 % and 76.2 %, respectively. These increased removal efficiencies were related to the lower N and P concentrations in the surface water of the paddy field and the efficient use of nutrients by rice under the reduced fertilization treatments. Compared to the NFR-F treatment, the 0.8NFR-E treatment resulted in a comparable accumulation of N and P and grain yield of rice, while decreasing the contents of N and P in the water of paddy fields and the residual soil N and P in the 0−60 cm soil depth after the rice harvest. Thus, reducing the normal fertilizer rate by 20 % could improve the water quality of the paddy field without deleterious effects on the rice yield and save 5700 m3 ha-1 of fresh water under fishpond effluent irrigation. These results can also provide a basis for in-depth understanding of the mechanism of aquaculture effluent purification through paddy field ecosystem in response to fertilizer supply levels.

Changes in metabolism, growth and nutrient uptake of Ulva fasciata (Chlorophyta) in response to nitrogen source

The form of inorganic nitrogen (N) determines the biofiltration performance of Ulva, particularly by inhibition of nitrate assimilation in the presence of ammonia. In the current study, Ulva fasciata from a biofilter of fishpond effluent was examined for its biomass production, photosynthetic activity, nutrient uptake and activity of nitrate reductase when supplied with either ammonia or nitrate as the sole nitrogen source. The effects of prior acclimation to either nitrogen source were also studied. Cultivation of Ulva with ammonia resulted in a rapid uptake of this nutrient, whereas photosynthesis, uptake of orthophosphate and C:N ratio were greater in cultures with nitrate. The transfer of Ulva from ammonia to nitrate nutrition increased carbohydrate content in the biomass. Longer culture in nitrate did not influence photosynthetic yields, growth, or N and P uptake rate by the algae, but increased both lipid and P content in biomass. Once transferred from ammonia-rich to nitrate-rich seawater, nitrate uptake by Ulva commenced immediately, although the activity of the enzyme nitrate reductase was first detected only 28 h later. Culture of Ulva in different nitrogen forms, ammonia and nitrate, may determine application of the resulting biomass in different industries, e.g., feeding, bioethanol, biofiltration, etc., considering the rapid production of protein-rich Ulva in the presence of ammonia, while yield is lower in the presence of nitrate but the biomass contains more carbohydrates and removes P from the effluent more rapidly.

Response of Fish Pond Effluent on Soil Chemical Properties and Growth of Cucumber (Cucumis sativus) in Igbariam South Eastern, Nigeria

The response of fish pond effluent on soil chemical properties and growth of cucumber (Cucumis sativus) in Igbariam South Eastern, Nigeria was studied during 2018 farming season at the Teaching and Research Farm of the Department of Soil Science, Faculty of Agriculture, Chukwuemeka Odumegwu Ojukwu University, Igbariam Campus, Anambra State, Nigeria. The field experiment which was laid out in a Randomized Complete Block Design (RCBD), comprised three treatments and three replications as follows: T1 – Control (No treatment): T2 – Fish Pond Effluent (40,000 litres/hectare) and T3 – Fish Pond Effluent (20,000 litres/hectare) + 200kg/ha fertilizer (NPK 20: 10:10). Results obtained revealed that, the treatments were significantly (P=0.05) different on some chemical properties of soil and Growth Parameters of Cucumber. The highest values of the Soil Chemical Properties (Available Phosphorus -6.6 mg/kg; Total Nitrogen -0.8g/kg; Organic Carbon – 5.8g/kg; Organic Matter – 10.1g/kg were recorded at the plot where Fish Pond Effluent was applied at the rate of 20,000 litres/hectare with 200kg/ha of fertilizer (NPK 20: 10:10). Fish Pond Effluent had no significant effect on the pH of the soil as the pH of the treated plots was almost at par with the Control. While the highest values of Number of leaves (37.9), Vine length (39.47cm) and Number of Branches (2.80) were also recorded at the plot where fish pond effluent was applied at the rate of 20,000L/ha with 200kg/ha of NPK fertilizer (20:10:10) at 7 WAP.

An integrated Ulva-periphyton biofilter for mariculture effluents: Multiple nitrogen removal kinetics

Biofilters made of Ulva and periphyton differ in their effectiveness in removing ammonia and nitrate from mariculture effluents. Our research evaluated the practicality of a combination of these two biofilters in improving the overall removal of dissolved N, where efficient removal of ammonia by the seaweed is followed by efficient removal of nitrate by periphyton. A paired Ulva-periphyton biofilter was exposed to various areal loads of ammonia and nitrate, the primary nitrogen forms in fishpond effluents.A first upstream macroalgae biofilter stocked with Ulva was fed with fishpond effluents at different areal loads of ammonia and nitrate, while a second downstream periphyton biofilter was paired for further nitrogen removal from the effluent. Ulva removed ammonia at a rate of 0.7–5.4 g TAN m−2 d−1, in correlation with the TAN areal load, with Vmax of 5.1 and Km of 4.4 g TAN m−2 d−1. Downstream periphyton was exposed to a lower TAN, but nitrate-rich effluent, and revealed similar capacities for the removal of both N forms, at removal rates of up to 1.7 and 1.8 g N m−2 d−1, respectively. Compared to nitrate, areal load of TAN had a greater impact on the removal dynamics of both N forms by periphyton. Overall, the paired biofilter resulted in a nearly total depletion of ammonia (97%) and efficient nitrate removal (67%), when areal loads in fishpond effluents were below 2 and 4 g N m−2 d−1 of TAN and NO3-N, respectively.