Impacts of effluents and wastes of shrimp processing industries on soil and water environment in and around Khulna city

Abstract

Dumping of solid and liquid wastes without treatment is a common practice and of great concern in Bangladesh. Most of the industries in Bangladesh do not follow the environmental compliance for ETP in their plants and release untreated wastes in the environment. There are 130 shrimp processing industries at present in Bangladesh of which 48 are located in and around Khulna city. These industries are mainly involved in processing and packaging shrimps for exporting to the world market. Due to the nature of the industries, substantial quantity of solid wastes and effluents are generated during the process and disposed off in the nearby agricultural lands, channels, canals, rivers, low lying areas, along road side ditches and water bodies. Fish processing activities involve production of large quantities of biodegradable solid organic wastes and by-products from inedible fish parts as well as effluents containing salts, fat-oil-grease (FOG), proteins, carbohydrates, suspended and dissolved solids, high levels of phosphates and nitrates, heavy metals and pathogenic and other micro flora. These waste streams can have extremely high biochemical oxygen demand (BOD) and chemical oxygen demand (COD) and if discharged without treatment into water bodies, the pollutants it contains can cause oxygen depletion in the environment and phytotoxicity. It is hypothesized that untreated wastes and effluents released in the environment from fish processing industries in and around Khulna city will have detrimental effects on receiving soils and water bodies. Crop production and crop quality is also expected to be affected. There are no systematic studies have yet been carried out in Khulna region to identify the nature of contaminants present in the wastes and effluents released and the impact on the environment. Systematic analysis of wastes and effluents for the identification of the pollutants and how these are affecting soil and water qualities and causing environmental quality degradation and crop damages deserve to be investigated. The Environmental Impact Assessment (EIA) was conducted in some selected areas in and around Khulna city. Twelve shrimp processing industries were selected for survey and soil and effluent samples were collected from four large industries for this study. Analysis of effluents, representative soil and water samples were conducted for different physical and chemical parameters as required in the investigation. Seed germination test and pot experiments were conducted to observe the effect of effluents on seed germination and on plant growth and yield. On ground survey of the shrimp processing plants in the present investigation are observed to be constructed on the road side agricultural lands surrounded by, rivers, canals, ponds and small water bodies and the wastes (6800Kg/day/plant) and effluents (47500L/day/plant) generated are directly released in the environment. None of the industries are following the compliance of ETP as required by ECR-97. Effluent released from the investigated shrimp processing industries contains various degrees of chemical species or substances that can affect soil and water, notable of which are pH (8.06±1.12), EC (15.21±2 mSCm-1), DO (1.7±0.12 mgL-1), TDS (1777±553 mgL-1), TSS (543±187 mgL-1), BOD (377±15 mgL-1), COD (593±10 mgL-1), HCO3-+ (28.8±5.95 mgL-1), SO42- (372±46 mgL-1), Cl- (0.9±0.06%), NH4+-N (50.17±32.06 mgL-1), NO3--N (12±1.5 mgL-1), Na+ (70±4 meqL-1), K+ (3.39±0.17 meqL-1), Ca2+ (9.3±0.42 meqL-1), Mg2+ (9.3±0.42 meqL-1), SAR (16.47±1.03), SSP (66.94±1.45%), Hardness (105.29±1.09 mgL-1), Zn (94.48±21.02 mgL-1), Mn (129±19 mgL-1), Pb (2.75±3.25 mgL-1), Cd (0.19±0.31 mgL-1), Cr (16.6±0.03 mgL-1), Ni (7.25±6.05 mgL-1), TC (2.9×103±0.6×103 c.f.u/100 ml), FC (235±76c.f.u/100 ml). The effluents also found to contain different levels of NH4+ and NO3- Nitrogen (92.6±3.2 mgL-1), PO43- (26.5±2.6 mgL-1), SO42--S (372±46 mgL-1), K+ (3.39±0.17 meqL-1), Na+ (70±4 meqL-1), Mg2+ (9.3±0.42 meqL-1), Ca2+ (9.3±0.42 meqL-1), DOC (233.6±70 mgL-1). Effluent characteristics significantly changed with distance travelled over a cross section of land. Concentrations measured at a distance of about 350m from the source point were- turbidity (305-665 NTU), temperature (24-27.5 0C), pH (7.48-8.18), EC (12.1-17.21 mScm-1), Salt (0.77-1.1%), DOC (186-328.67 mgL-1), DO (0.15-1.82 mgL-1), TDS (1320-2350 mgL-1), TSS (366-966 mgL-1), BOD (367-436 mgL-1), COD (572-980 mgL-1), HCO3- (16.02-34.75 mgL-1), SO42- (306-485 mgL-1), Cl- (0.73-0.96%), NH4+-N (7.57-92.87 mgL-1), NO3 -N (10.7-17.9 mgL-1), Na+ (42-71 meqL-1), K+ (2.7-3.91 meqL-1), Ca2+ (23.72-27.22 meqL-1), Mg2+ (6.75-9.72 meqL-1), Hardness (87.16-106.38 mgL-1), Zn (68.3-124.7 mgL-1), Mn (99-165 mgL-1), Pb (1-8 mgL-1), Cd (0.05-0.59 mgL-1), Cr (16.1-18.7 mgL-1), Ni (3.3-13.3 mgL-1), TC (2.3×103-4.75×103c.f.u/100 ml) and FC (110-411c.f.u/100 ml). The chemical properties of the soils receiving effluents were also changed, notable of which are pH (7.2-7.74), EC (4.27-6.69 mScm-1), Percent Salt (0.27-0.43), CEC (12.2-29.7 meq100g-1 soil), OC (2.04-2.98%), OM (3.51-5.13%), Total N (0.14-0.21%), Available N (38.2-137.75 mgKg-1), C:N ratio (12.81-18.47), S (18.75-32.1 mgKg-1), P (14.2-24.1 mgKg-1), Na+ (74.89-193.5 meq100g-1 soil), K+ (2.79-5.83 meq100g-1 soil), Ca2+ (10.88-12.41 meq100g-1 soil), Mg2+ (2.88-3.71 meq100g-1 soil), Zn (88.4-200.6 mgKg-1), Mn (350-928 mgKg-1), Pb (1-10 mgKg-1), Cd (0.2-0.8 mgKg-1), Cr (32.4-49.3 mgKg-1) and Ni (20.4-47 mgKg-1). Seed germination tests carried out with the raw and diluted effluent showed comparable results with three different plant species namely Red amaranth (Amaranthus curentus), Stem amaranth (Amaranthus lividus) and Water spinach (Ipomoea aquitica). The application of raw effluent significantly reduced seed germination of different species up to a level of 24%, however Stem amaranth (Amaranthus lividus) was mostly affected and the order was SA>RA>WS. The recovery of the effect on seed germination was observed at a dilution of 75%. Pot experiments carried out to assess the effect of effluents with or without dilutions on growth and yield of Red amaranth (Amaranthus curentus), Stem amaranth (Amaranthus lividus) and Water spinach (Ipomoea aquitica) showed to have significant effects on the growth parameters and biomass production like the number of leaves/plant, Fresh weight/plant, dry weight/plant and percent moisture content compare to the control treatment (uncontaminated soil) and the order was SA>RA>WS. Soils treated with raw effluents reduced the number of leaves per plant (38.1%), fresh weight per plant (50.14%), dry weight per plant (42.57%) and percent moisture content (6%) in Red amaranth; reduced the number of leaves per plant (46.14%), fresh weight per plant (47.21%), dry weight per plant (47.49%) and percent moisture content (7.32%) in Stem amaranth and reduced the number of leaves per plant (48.51%), fresh weight per plant (27.79%), dry weight per plant (35.51%) and percent moisture content (8.42%) in Water spinach. The effects were recovered at a dilution level of 75%. Uptake of N, P and S was reduced in raw effluent treated crops and the effects were recovered at a dilution level of 50%. Treatment with raw effluent reduced uptake of N to a level of 49.09% in RA, 36.81% in SA and 47.03% in WS; Phosphorous up to 47.89% in RA, 58.6% in SA and 59.86% in WS and S up to 53.8% in RA, 52.84% in SA and 37.93% in WS. Raw effluent treated plants accumulated reduced levels of Ni, Mn, Cr and Zn compared to the control treatment i.e. 54.88% reduction of Ni in RA, 81.36% in SA and 62.48% in WS; 50.17% Mn in RA, 50.44% in SA and 43.33% in WS; 60.69% Cr in RA, 74.43% in SA and 63.19% in WS and 33.09% Zn in RA, 46.6% in SA and 40.85% in WS. Environmental Impact Assessment (EIA) of the wastes and effluents released from the fish processing industries confirmed potential negative impacts on soil physical and chemical properties and water quality around the industries. It is evident from the results that untreated effluents released in the environment from different shrimp processing industries can have significant level of damaging effects on soil and water quality and crop production though some positive effects as well. The effluents analyzed for different physical, chemical and biological parameters showed presence of chemical species and substances that can have detrimental effects on soil biota and can change physical and chemical properties of soils. The effluents also showed to contain chemical species like N, P, S, OC, K+, Na+, Mg2+, Ca2+, Ni, Zn and Mn that can be a potential source of nutrients if applied as irrigation water after removal of unwanted toxic chemical species and reduction of salt contents. It is also noted that none of the industries of shrimp processing plants have ETP and they are not following the compliance of ECR-1997. The installation of ETP required to be enforced for all industries. Khulna is the most fish producing region in the country, and the surface water quality of this area is very important. If the surface water quality is affected, the production and quality of fish may also be affected and can have negative impacts on export and thus on our national revenue.